Linux & Python for Raspberry Pi: Getting started with Linux & Python

1. Installation
	1.1 Introduction
	1.2 Os(Rasbian) Installtion
	1.3 Development Environment
2. Linux Basic
	2.1 Introduction to Unix & Linux
	2.2 Linux Command Syntax
3. Linux File System
	3.1 File & Directory Command
	3.2 Standard I/O
	3.3 File Permission
	3.4 File System and Link
4. Shell Scripting
	4.1 VI Editor
	4.2 Shell programming
5. Process & System
	5.1 Process
	5.2 System Initialization
	5.3 User
	5.4 Utilities & APT
6. Python Basic
	6.1 Introduction
	6.2 Syntax
	6.3 Data Structure
	6.4 Function
	6.5 Module
	6.6 Class
	6.7 Exception
	6.8 File I/O
	6.9 Thread
	6.10 Networking
7. Python Web Programming
	7.1 Introduction
	7.2 HTTP
	7.3 Flask
	7.4 WebSocket
	Chapter2: Raspberry-Pi for Prototyping
1. Raspberry-Pi & GPIO
	1.1. GPIO
	1.2. Digital Output
	1.3. Digital Input
	1.4. Analog Output – PWM
	1.5. Analog Input – RC Circuit
	1.6. High Level Sensor Modules
2. Raspberry-Pi Communication
	2.1 Serial Communication
	2.1 UART
	2.1 I 2 C
	2.1 SPI
	2.1 Bluetooth
	2.1 BLE - Beacon
3. Raspberry-Pi Multimedia
	3.1 Buzzer
	3.2 Audio
	3.3 Camera
	3.4 CCTV
	3.5 OpenCV Computer Vision
8. Raspberry-Pi Web IoT
	8.1 Introduction
	8.2 Web with GPIO
	8.3 Camera Web Streaming
9. Appendix
	9.1 Arduino
		  Raspberry-Pi
			 https://en.wikipedia.org/wiki/Raspberry_Pi
			 Eben Upton, UK Raspberry Pi Foundation Founder
			 For teaching computer science in developing countries
			 2011, Alpha board
			 2012, First sales
			 Broadcom BCM2835 SoC
			 Designed as a PC, Not a development board
		  Raspberry Pi Boards Series
			 https://www.raspberrypi.org/products/
		 Raspberry Pi Boards Series
		 Raspberry Pi 3
			 ARMv8 CPU 1.2GHz 64bit quad-core
			 802.11n Wireless LAN
			 Bluetooth 4.1
			 Bluetooth Low Energy(BLE)
			 1GB RAM
			 4 USB ports
			 40 GPIO Pins
			 Full HDMI port
			 Ethernet port
			 3.5mm audio
			 Camera interface(CSI)
			 Display interface(DSI)
			 Micro SD card slot
			 VideoCore IV 3D graphics core
		 Raspberry Pi 3
		 OS image file download
			 https://www.raspberrypi.org/downloads/raspbian/
			 201x-xx-xx-raspbian-jessie.zip
			 Raspbian
				 Jessie with PIXEL : Full Image with PIXEL Desktop
				 Jessi Lite : Minimal Image
		 Burn Image to SD Card
			 ETCHER
				 https://etcher.io/
				 Windows, MacOSX, Linux
			 Win32Disk Imager
				 https://sourceforge.net/projects/win32diskimager/
				 Windows Only
					
		 setup
			 As a PC
				 Connect Monitor, Keyboard, Mouse and Internet
				 Network setup
				 SSH Connection
			 As a develop board
				 Serial Consol TTY
					 USB-Serial Convertor
					 USB(PC) to UART(R-Pi)
					 Network setup
					 SSH Connection
				 Direct Ethernet cable(Internet Sharing)
					 Ethernet(PC) – Ethernet(R-Pi)
					 Network setup
					 SSH Connection
		 As a PC
			 Easiest way to setup but inconvenient
			 Connecting
				 Monitor using HDMI Cable
				 Mouse/Keyboard using USB
				 Ethernet Cable
			 Insert SD Card
			 Power In
		 As a PC
			 open editor as sudo
				 Run
				 sudo leafpad
		 As a PC
			 static IP setup
				 File > Open
				 /etc/dhcpcd.conf
		 Serial Console TTY Enable
			 Eject SD card reader and Connect to PC again
			 Check ‘boot’ drive and 2 files in it
				 cmdline.txt
				 config.txt
			 cmdline.txt (Just checking)
			 config.txt
				 add “enable_uart=1” at the end of the file
				 no spaces in the line
			 Eject SD card from PC, Insert into R-Pi SD slot
				 No Powering to Raspberry Pi yet.
		 Static IP setup
			 sudo vi /etc/dhcpcd.conf  (Must Back-up)
			 sudo reboot
			 ifconfig eth0
				 Check IP address
		 Network Check
			 ip
				 ifconfig
				 ip address
			 Router
				 route
				 ip route
			 DNS
				 cat /etc/resolv.conf
		 Wifi setup
			 sudo iwlist wlan0 scan
			 sudo vi /etc/wpa_supplicant/wpa_supplicant.conf
			 sudo ifdown wlan0
			 sudo ifup wlan0
			 ifconfig wlan0
				 Check IP address
		 SSH Login
			 PuTTy
				 Connection Type : SSH
				 Host Name : Raspberry  Pi IP Adress
				 Port : 22
				 Save RSA Key
			 Login
				 ID : pi
				 Passwrd : raspberry
		 Software Configuration
			 sudo raspi-config
				 4 Internationalisation options
					 Time Zone > Asia > Seoul
					 Change Locale
				 en_US.UTF-8
					 ko_KR.EUC-KR
					 ko_KR.UTF-8
					 Default : en_US.UTF-8
				 Change Keyboard layout
					 Generic 105-Key
					 Korean-104Key Compatible
			 Module Update
				 sudo apt-get update
				 sudo apt-get upgrade
			 Install Korean Font
				 sudo apt install fonts-unfonts-core
			 Install Korean Keyboard Input
				 sudo apt install ibus
				 sudo apt install ibus-hangul
		 LCD Monitor setup
			 http://elinux.org/index.php?title=RPiconfig
			 /boot/config.txt
				 BIOS in PC
			 max_usb_current
				 Change Usb output limits
				 600mA j1200mA
			 hdmi_group
				 1 : CEA, 2: DMT
			 hdmi_mode=87
				 Custom mode
			 hdmi_cvt
				 width, height, framerate, aspect, margins, interlace, rb
		  Remote Desktop - VNC
			 Raspberry-Pi Configuration GUI
				 Interfaces
					 Enable VNC Service
			 Raspberry-Pi Configuration CLI
				 sudo raspi-config
					 Interfaces
						 VNC
		 Remote Desktop - VNC
			 Raspberry-Pi
				 Server Installation
					 sudo apt-get install x11vnc
				 Execute Server
					 x11vnc
				 Adjust Resolution
					  http://elinux.org/Rpiconfig
					 /boot/config.txt
		  Remote Desktop - VNC
			 PC
				 http://www.realvnc.com/download/
				 Install VNC Viewer
		 Remote Desktop - xrdp
			 Raspberry-Pi
				 Server Installation
					 sudo apt-get remove vnc4server
					 sudo apt-get remove tightvncserver
					 sudo apt-get install tightvncserver
					 sudo apt-get install xrdp
				 File for server setting
					 /etc/xrdp/xrdp.ini
			 PC(Windows Only)
				 Start > mstsc (Remote Desktop)
				 sesman-XVnc
				 pi / raspberry
		 Python
			 https://www.python.org/downloads/release/python-2711/
			 Version 2.7.x, Not 3.5.x
		  Python
			 Installation on PC
			 Default Path
			 Enable "Add python.exe to path" Option
		 Python
			 Hello World
			 REPL(Read-Eval-Print-Loop)
				 open Windows command console
				 execute 'python' command
				 python shell prompt opened
				 execute 'print "Hello world"
				 command 'exit()'
			 Source Code
				 make a file named 'hello_world.py'
				  execute command
					 python hello_world.py
		 WinSCP
			 SFTP : FTP based on SSH
			 Transfer/ Receive File
			 https://winscp.net/eng/download.php
		 WinSCP
			 Installation
			 Default Options
		  WinSCP
			 Connect to RaspberryPi
		 WinSCP
			 Left Pannel : PC Local File System
			 Right Pannel : Remote, RaspberryPi File System
			 File upload : File > Upload  (F5) to /home/pi
		  Python on RaspberryPi
			 Open PuTTY
			 Check the file "hello_world.py" uploaded
				 ls hello_world.py
			 Execute
				 python hello_world.py
		 GCC Cross Compiler for RaspberryPi
			 http://gnutoolchains.com/raspberry/
			 Appropriate version for Raspbian Image installed
		  GCC Cross Compiler for RaspberryPi
			 Install on PC
			 Default Options
		  GCC Cross Compiler for RaspberryPi
			 Check Installation
			 C:\SysGCC\Raspberry\bin\arm-linux-gnueabihf-gcc  --version
			 Source Code "hello_world.c"
				 make file named hello_world.c
		  GCC Cross Compiler for RaspberryPi
			 Compile
				 arm-linux-gnueabihf-gcc  -o hello_world hello_world.c
				 Check the output file named "hello_world"
			 Upload to RaspberryPi using WinSCP
				 /home/pi/hello_world
			 Check and change permission the file on RaspberryPi
				 ~$ file hello_world
				 ~$ chmod 777 hello_world
			 execution the file
				 ~$ ./hello_world
		  NodeJs
			 Download for PC(Windows)
			 https://nodejs.org
			 LTS Version
		  NodeJs
			 Installation on PC
			 Default Options
		 NodeJs
			 Download for RaspberryPi
			 Too old version(v0.10.x) is installed by default
			 Determine download version with CPU archtecture
				 $ uname –m or  $ lscpu or $ cat /proc/cpuinfo
				 RaspberryPi CPU is ARMv8, but Rasbian OS is based on 32bit
		 NodeJs
			 Download
				 wget https://nodejs.org/dist/v6.9.4/node-v6.9.4-linux-armv7l.tar.xz
			 Extract
				 tar –xf node-v6.9.4-linux-armv7l.tar.xz
			 move to /opt
				 sudo mv node-v6.9.4-linux-armv7l /opt/nodejs
			 create link
				 apt-get remove nodejs
				 sudo ln –s /opt/nodejs/bin/node /usr/bin/node
				 sudo ln –s /opt/nodejs/bin/npm /usr/bin/npm
		 NodeJs
			 check nodejs version
				 $ node –version
			  Source Code
				 make the file named 'hello_world.js' on PC
				  Run on PC
					 node hello_world.js
			 Upload and Run on Raspberry
				 upload the file using WinSCP
				 node hello_world.js
		 JDK(Java Development Kit) Installation
			 Needed for Eclipse
				 http://java.sun.com
				 http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
		 Eclipse Installation
			 http://www.eclipse.org/downloads/
			 Eclipse IDE for JavaEE Developer
		  PyDev Installation
			 Eclipse > Help > Eclipse Marketplace
			 Search "Python"
		 PyDev Configuration
			 Eclipse Preferences
			 Pydev > Interpreters > Python Interpreter
			 Quick Auto-Config
		  Python Project
			 Create a Python new project
				 New  > Project
			 Create a Python Source Code File
				 New > PyDev Module
		 Python Project
			 Python Code
			 Running
				 R Click > Run As > Python Run
		 Eclipse CDT(C/C++ Development Tooling) Installation
			 Eclipse Help > Install New Software
			 Click Add Button
			 Name : CDT
			 Location : http://download.eclipse.org/tools/cdt/releases/9.2
		  Eclipse CDT(C/C++ Development Tooling) Installation
			 Eclipse Help > Install New Software
			 Add Button Click
			 Name : CDT
			 Location : http://download.eclipse.org/tools/cdt/releases/9.2
			 check all items
				 uncheck Arduino C++ Tools
		  C Project
			 R Click  > New Project
		 C Project
			 Fill in the Project Name
			 Project Type
				 Hello World ANSI C Project
			 Toolchanis
				 Cross GCC
		  C Project
			 Basic Settings
				 Fill in the blanks appropriately
		 C Project
			 Select Configurations
				 Leave it as defaults
				 Checked Debug, Release
		  C Project
			 fill in the blanks correctely
			 cross compiler prefix
				 arm-linux-gnueabihf-
			 cross compiler path
				 C:\SysGCC\Raspberry\bin
				 Path of the Cross Compiler
		 C Project
			 C Source code
			 Build
				 Menu > Project > Build All
			 Check the result
				 Console message
				 output file under Debug
		 C Project
			 Running
				 Upload using WinSCP
				 Execute the file on the RaspberryPi using PuTTY
		 Eclipse NodeJs Configuration
			 Nodejs Plugin Installed by default on Eclipse Neon
			 Check the Configuration
			 You can customize
		  NodeJs Project
			 Create a Nodejs Project
				 R Click > New Project > Javascript Project
		 NodeJs Project
			 Fill in the project name
			 Leave all other items as default
			 Click Finish
		  NodeJs Project
			 Create Source Code File
				 R Click > New > File
				 Fill in the File Name with .js extention
				 Click Finish button
			 Edit File
			 Running
				 R Click > Run As  > Node.js Application
				 Check the result on the Console
		 RemoteSystem Setup
			 You can control the Remote RaspberryPi with Eclipse
			 Open Perspective
				 Eclipse > Window > Perspective > Open Perspective > Other
				 Remote System Explorer
		  RemoteSystem Setup
			 Register a new Connection
			 Remote System > R Click
		 Login
		  Apply Python Project to Remote
			 Export project produced in PyDev Perspective
			 Remote Systems > Remote File System
		 Apply Python Project to Remote
			 Select a directory on RaspberryPi
		  Apply Python Project to Remote
			 Select Destination
			 Check "Review/Sysnchronize" Option
		 Apply Python Project to Remote
			 Put the file to apply using Synchronize view
		 Apply Python Project to Remote
			  Executing remotely using PuTTY.
		 Apply C Project to Remote
			 R Click on the Project
			 Run As > Run Configurations
			 Select "C/C++ Remote Application"
			 create new run configuration
			 new connection
			 connection type
			 SSH
		 Apply C Project to Remote
			 New Connection
				 Fill in the blanks
			 Remote path
				 Select properly path on the remote Raspberry Pi
		 Apply C Project to Remote
			 Commands to execute before application
				 chmod 744 path/to/output_file_name
			 Check the result in the Console view
		 Apply NodeJs Project to Remote
			 NodeJs Project Export
			 Remote Systems > Remote File System
			 Select a directory on RaspberryPi
			 Check "Review/Synchronize" option
		 Apply NodeJs Project to Remote
			 Put the file to apply using Synchronize view
			  Executing remotely using PuTTY.
		 Unix
			 Multics for GE646 by AT&T, GE, MIT in 1964
				 Multi User, Multi Processing, Multi Process
				 Pulled down for many problems in 1969
			 Unix
				 AT&T Lab
				 1971' Re-do in Assembly by  Ken Thompson(US, 1943 ~ )
				 1973' Re-written in C language by Dennis Ritchie
					 US, 1941 ~ 2011
					 Developed C language to Write Unix
				 UC Berkley
					 Buy Source Code from AT&T
					 Added TCP/IP Stack
					 BSD version
				 System V from AT&T
					 Solaris, HP-UX, AIX
				 BSD from UC Berkley
					 SunOS, FreeBSD
		 Minix
			 Minimal Unix-like OS, 1987 Andrew Stuart(Nederland, 1944~)
			 For Education only
		 Linux
			 1991' University of Helsinki, Linus Torvalds(Finland, 1969~)
			 Created Unix like OS on Minix
			 Free Software, GNU GPL
		 Distributions
			 Red Hat
				 Famous in Enterprise Server
				 Package Manager : RPM
				 Fedora, CentOS, 붉은별
			 Debian
				 Famous in Desktop
				 Package Manager : APT
				 Ubuntu,  Rasbian, Mint
			 Slack ware
				 OpenSUSE, Slax
		 Unix like System
			 Minix
			 Linux
			 Mac OSX
		 POSIX(Portable Operating System Interface)
			 suggested by Richard Stallman(1953 ~ ) in 1985
			 Standards for Unix Interface
			 Certified
				 AIX
				 HP-UX
				 IRIX
				 macOS, Darwin
				 Solaris
				 FreeBSD
				 NetBSD
				 Linux
				 VxWorks
		 Unix/Linux System Structure
			 Kernel
			 File System
			 Shell
		 Kernel
			 Core Component
			 Device Management
			 Memory, Process Management
			 File System Management
			 CPU Control
		 File System
			 Hierarchical Directory and File, /(root)
			 Managing Files in Disks
			 Mapping Devices, Processes to Files
			 Linux FS
				 Ext3, Ext4
		 Shell
			 Interfacing between Human and Kernel
			 Shells
				 Bourne Shell
					 Unix Orinate
				 C Shell
					 Similar C language
				 Korn Shell
					 Unix Standard
					 Improved Bourne & C
				 Bash Shell
					 Most Linux Shells
					 Bourne Again
				 Z Shell
					 Mordern Style
		  Command Line Interface
			 Command
				 Shell Built-in Command
				 Execution File in PATH
			 Options
				 Optional
				 dash(-) character
				 Additional Requirements
				 Modifiers for Command
			 Arguments
				 Optional or Mandatory
				 Object of Command
				 Target to Execute
		 Command Line Interface
			 Command Only
				 No options
					 Default Options
				 No arguments
					 Objects or Targets omitted
				 Examples
					 uname
					 date
					 cal
					 ls
		 Command Line Interface
			 Command + Options
				 Additional Requirements
				 Common Options
					 -a : all
		 Command Line Interface
			 Command + Arguments
				 Target Specific
				 No omitted
		 Command Line Interface
			 Command + Options +  Arguments
		 Command chaining
			 Executing Multi Commands Simultaneously
			 ; - Semi Colon(;)
				 command-1; command 2; command-n
				 sequential Separated N command
				 No effect error
			 && - Ampersand X 2
				 No Single & (Background)
				 Depends on Error
				 Stop If Error Occurs
		 Control Characters
			 Process
				 Ctrl + c :  Interrupt(terminate) current process, SIGINT
				 Ctrl + d : EOF(End of File) or EOT(End of Transmission) Character
				 Ctrl + z : Suspend current foreground process, SIGSTP
			 Cursor
				 Ctrl + a : move cursor to start of line
				 Ctrl + e : move cursor to end of line
			 Screen
				 Ctrl + u : Clear current line
				 Ctrl + w : Clear current word
				 Ctrl + l : Clear screen
				 Ctrl + s : Stop output to the screen
				 Ctrl + q : Resume output to the screen stopping with Ctrl + s
		 Types of Command
			 Shell Built-in
				 Internal Command
				 Shell Command
			 Executable Program File
				 External Command
				 All Files has X mode in disk
				 Specified the location in $PATH env
					 /bin : basic command for normal users
					 /sbin : basic command for administrators
					 /usr/bin, /usr/sbin : command for specific class user
						 ex : office user,  developer, gamer
					 /usr/local/bin, /usr/local/sbin : user compiled, installed program
		  Types of Command
			 Shell Built-in
				 List up
					 help
				 Detail Information
					 help 
				 Distinguish
					 type 
			 Executable Program File
				 List up
					 echo $PATH
				 Detail Information
					  --help
					 man help
				 Location
					 which 
		 Manual page
			 From Unix Manual Paper Book
				 online : http://man7.org/linux/man-pages/index.html
		 Manual page
			 man 
				 Navigate key
					 enter : next line
					 space : next page
					 b : prev page
					 /pattern : search pattern
					 n : next pattern
					 q : exit
				 SEE ALSO
					 Relative Command
				 Section Number
					 Command(n)
		 Manual page
			 Inquiring in section
				 man –s  
				 man  
			 Keyword
				 man –k 
		 pwd
			 present working directory
		 ls
			 list up files and directories
			 ls options pathname
			 -l : long, detail
			 -a : all, no hidden file
			 -d : directory
			 -R : recursive
			 -F : file type
				 / : directory
				 * : executable
				 (none) : text
				 @ : link
			 ls file
			 ls /dir
		 ls -l
		 Tree
			 list directory like tree-format
				 -d : directory only
				 -L : depth level
				 -P  : pattern only
				 -I  : ignore patten
		 File
			 determine file type
				 -i : MIME type
				 -L  : symlink
		 Stat
			 display file or file system status
		 Directory Command
			 mkdir
				 make directory
				 -p : make parent
			 cd
				 change directory
				 Path
					 Absolute vs Relative
				 .  : current dir
				 .. : parent dir
				 ~ : home dir
				 / : root dir
				 - : previous
		 Making a File
			 touch 
				 no content in the file
				 zero size
			 echo 'content' >  
				 echo  'hello world' > hello.txt
				 echo & redirection
			 Editor
				 nano 
				 vi 
		 Nano Editor
			 Linux Basic Test Editor
			 nano [FILENAME]
				 Ctrl + X : eXit
				 Ctrl + O : Save
				 Ctrl + K : Cut, Copy
				 Ctrl + U : Paste
				 Ctrl + ^ : Block
				 Ctrl + W : Search
				 Ctrl + G : Help
		 cp (Copy)
			 Copy File or directory
			 cp option source target
			 File Copy
				 new file name
					 cp fileA fileAA
				 new file name to other dir
					 cp fileA dirA/fileAA
				 no file name to other dir
					 cp fileA dirB
				 -i : Interactive
					 prevent overwriting
		 cp (Copy)
			 Directory Copy
				 -r : recursive
				 To new directory
					 cp –r dirA dirZ
					 create new directory
				 To existing directory
					 cp –r dirA dirB
					 copy to child directory
		 mv (Move)
			 Move File or Directory
			 To Move File
				 File name only
					 mv fileA fileX
					 The same with rename
				 New path
					 mv fileB dirB/fileX
		 mv (Move)
			 To Directory
				 To new directory
					 mv dirA dirX
					 create new directory
				 To existing directory
					 mv dirB dirC
					 move to child directory
		 rmdir (Remove Empty Directory)
			 rmdir [option] DIRECTORY...
				 -p : parent
					 Remove ancestors
				 only empty directory
				 if not empty
					 fail
					 use rm
		 rm (Remove File or Directory)
			 rm [options] file_path
				 -r : recursive
					 Not Empty
				 -f : force
					 ignore nonexistent
				 -d : empty directory
		 Display File content
			 cat [OPTION] [FILE]
				 concatenate file to output
				 If no file, standard input
			 more FILE
				 paging one screen
				 scroll
					 enter : next line
					 space : next page
					 b : prev page
					 / : search
					 n : next pattern
					 q : quit
			 head [OPTION] [FILE]
				 output the first part
				 -n  : first NUM lines
			 tail [OPTION] [FILE]
				 output the last part
				 -n : last NUM lines
				 -f : following
		 wc (Word Count)
			 wc [OPTION] FILE
			 no option : lines, words, bytes
			 -l : line counts
			 -w : word counts
			 -c : byte counts
			 -m : character counts
			 useful with pipe(|)
		 grep
			 grep [OPTION] PATTERN [FILE..]
			 print lines matching a pattern
			 OPTION
				 -i : Ignore case
				 -l : print file name
				 -n : line number
				 -v : invert match
				 -c : count
				 -w : word searching
				 -E : extended regexp
				 -F : fixed string
				 -r : recursive
		 egrep
			 grep -E
		 fgrep
			 grep –F
		 rgrep
			 grep -r
		 find
			 search files
			 find path expression action
				 expression
					 -name  filename
						 'filename*' : * with quotation mark
					 -type filetype : f, d, c, b ...
					 -size  [+|-]n[c,k,M,G]
					 -atime, -amin, -mtime, -mmin, -ctime, -cmin [+|-]n
					 -user owner_id
					 -perm [-|/] mode
						 - : match all bit
						 / : match any bit
					 -maxpeth n
		 find expression
		 find expression
		 find –perm
		 find
			 search files
			 find path expression action
				 action
					 -print(default) : path and name
					 -ls : print detail
					 -delete : delete files
					 -exec  command  [{}]  \;
					 -exec  command  {}  +
						 execute command
						 {} : Result of find
						 \; : execute separately
						 + :  execute at once
					 -ok command  [{}] \;   :  execute command interactively
		 find action
		 find –exec
		 Standard  I/O
		 Redirection
			 Input from file instead of stdin
				 < file_name
			 output to file instead of stdout
				 > file_name : overwrite
				 >> file_name : append
			 output to file instead of stderr
				 2> file_name : overwrite
				 2>> file_name : append
		 Redirection
			 /dev/null
				 Null Device
				 Special File to discard useless data
				 command  2> /dev/null
					 discarding useless error messages
			 > file_name 2>&1
				 Redirecting stdout, stderr to same file
		 Pipe ( | )
			 Connect stdout of process(A) to stdin of another process(B)
			 A | B
		 tee
			 Read from stdin, write to stdout and file
			 Good for output both stdout(terminal) and file
			 Using Redirection and Pipe Together
			 -a : append
		 Linux File Mode
			 Determine can read, write, execute
			 File type
				 - :  Normal file
				 d : Directory
				 l  : Symbolic link
				 s  : socket
				 p : Named Pipe
				 c : Character device
				 b : Block device
			 User
				 Owner
					 Owner ID
				 Group
					 Member of the group
				 Other
					 Not a owner, Not a member
		 File Permission
		 Determine Permission
			 id [USER]
				 print user and group
		 Change Permission
			 chmod mode filename
				 symbolic mode
					 Target
						 u : owner
						 g : group
						 o : other
						 a : all (default, except umask bit)
					 Operator
						 + : add
						 - : remove
					 = : assign
					 Permission
						 r : read
						 w : write
						 x : execute
		 Change Permission
			 Symbolic mode
		 Change Permission
			 chmod mode filename
				 Octal mode
					 3 digit in octal
		 Change Permission
			 Octal Mode
		 Change Owner
			 chown id FILENAME
			 chown id : group FILENAME
			 chown :group FILENAME
		 Change Group
			 chgrp gid FILENAME
		 Umask
			 newly created file's permission
			 umask : print umask
			 umask value : set umask
		 Umask Calculation
			 Default – Umask_value
				 2's Complement of umask
				 AND operation
			 Default Permission
				 Directory : 777
				 File : 666
			 Example, umask=0022
		 Umask
		 File System
			 Control how data(File) is stored and retrieved
			 Windows : FAT, NTFS, exFAT
			 Unix : UFS
			 Linux : Ext2/3/4, XFS,JFS
			 MacOS : HFS
			 Flash : UBIFS, JFFS2, YAFFS
		 Linux File System
			 Boot Block (Boot Sector)
				 At the beginning of Storage
				 Special data to start a system
			 Super Block
				 File system metadata (Type, Size, Status)
				 Information of I-Node, Data block
			 I-Node Block
				 Represents a File
				 Stores data of permission, owner, size,  pointer of Data Block
			 Data Block
				 Contain file data and directory
				 can be multiple per file
		 I-Node & Data Block
			 ls –il
				 -i : inode
		 Directory
			 Directory is a file
			 Stores file list
				 Pair of I-Node number and file name
			 Link Count
				 Every Directory has 2 items
					 . (Current)
					 .. (Parent)
				 Sub Directory Count
		 Link
			 Connection between a file and data
				 Hard Link
					 Low-level link
					 Make another File Name
					 But not make I-Node, has the same I-Node number
					 No difference between the original and the link
					 Increment Link Count
					 Cannot make a hard-link to directory
				 Soft(Symbolic) Link
					 Similar to Windows shortcut icon
					 Make a new file pointing to the original file
					 File Type : l, @
					 Permission : 777
		 Link
			 Update and Read
				 Always the same effect
				 Original, Hard-link, Soft-link
		 Remove Link
			 Remove origin
				 No effect  on hard-link
				 Make Dangling soft-link
					 Restorable, Creating a file with the same name as origin
			 Remove hard-link
				 No effect on origin, soft-link
			 Remove soft-link
				 No effect on origin, hard-link
		 Finding Link
			 Hard link
				 find . -samefile 
				 find . -inum 
			 Symbolic link
				 find . -lname 
		 vi [File Name ]
			 Mode
				 command mode
				 edit mode
				 last line mode: Input command at the last line
		 Vi  Edit Mode
			 i : Input in front of curser
			 a :  Input after the curser
			 o :  Input after adding a line at the end of curser
			 O : Input after adding a line before curser
			 A : Input at the end of curser line
			 I : Input in front of curser line
			 r : Overwrite one unit at the curser position
			 R : Overwrite exiting character from curser position
			 x : Delete a unit
			 dd : Delete a line
			 u : Redo
		 Vi  Moving Curser
			 h : Move left
			 j : Move down
			 k : Move up
			 l : Move right
			 ^ , 0:  To the beginning of the line
			 $ : To the end of the line
			 G : To the end of the document
			 1G : To the beginning of the document
			 Number G : Move to number line
			 Ctrl + D : A half page down
			 Ctrl + F : A half page up
			 Ctrl + B : One page up
			 Ctrl + U : One page down
		 Vi Copy/ Paste
			 yy : Copy the line with curser
				 Number yy : Copy lines as numbered
			 x : Cut one unit where the curser is located
			 p : Paste
				 Number p : Paste lines as numbered
		 Block Mode
			 v : Blurred Mode
			 y : Block Copy
			 p : Block Paste
			 d : Block Delete
			 > : Block Tap
			 < : Remove Block Tap
			 v , Ctrl + v : Block Column Mode
		 Vi Setting
			 :set nu
				 Show line number
			 :set showmode
				 Show mode
			 :set nonum
				 Hide line number
			 :set ai
				 Auto indent
			 :set cindent
				 C language style indent
			 :set list
				 Show special character
			 :set
				 Show set vi variables
			 :se all
				 Show all variables and set values
			 Save setting
				 ~/.vimrc
		 Vi Breaking Window
			 Open new window
				 Ctrl + w, n :
			 Transfer windows
				 ctrl +ww
			 Close window
				 ctrl +w, q
		 Vi Save, Shut down
			 :w [File Name]
				   Save
			 :e File name
				  Open file
			 :q
				 Shut down
			 :q!
				 Forced shut down
			 :x
				 Save and shut down
		 Meta-characters
			 Glob Patterns : wildcard characters whith file names
				 * : matches any characters
				 ? : matches any single character
				 [ ] : matches one charater given in the bracket
			  ( ) :  sub shell
			 $( ) : command substitution
		 Variables
			 Name : alphabet, number(no first letter), _(under score)
			 MY=value : make a variable
			 compgen –v : listup defined variables
			 unset : remove variable
			 export : exports variable to child process
		 Variables
			 Environment Variable : Valid System Wide
				 PATH, HOME, PS1, TERM, SHELL, LOGNAME
			 Special Variables
				 $$ :  current PID
				 $# : number of arguments
				 $0 : filename of current script
				 $n : arguments (n is positive decimal)
				 $? : exit state of last command executed
				 $! : PID of last background command
		 read
			 read a line from stdin and save to variable
		 expr
			 evaluate expression
		 exit
			 Exit the shell with a status of N
		 Quotes
			 ' : Single quotation, Ignore meta-character
			 " : Double quotation,  Ignore meta-character except 3 character
				 $, `, \
			 ` : backtick, command substitution
		 test express, [ express ]
			 evaluate conditional expression
				 Exit status : return 0 to true, 1 to fa
		 String Operators
			 = : check if equal
			 != : check if not equals
			 -z : check if size is zero(empty string)
			 -n : check if size is non-zero
		 Arithmetic Operator
			 A –eq B : check if A is equal to B , ==
			 A –ne B : check if A is not equal to B, !=
			 A –gt B : check if A is greater than B, >
			 A –lt B :  check if A is less than B, <
			 A –ge B :  check if A is greater than or equal to B, >=
			 A –le B: check if A is less than or equals to B, <=
		 File Test Operators
			 -d file : check if file is a directory
			 -f file : check if file is a normal file
			 -r file : check if file is readable
			 -w file : check if file is writable
			 -x file : check if file is executable
			 -s file : check if file has size greater than 0
			 -e file : check if file exists
		 Boolean Operators
			 ! : logical negation
			 -o : logical OR
			 -a : logical AND
		 Decision Making
			 if ~ then ~ fi
			 if ~ then ~ else ~ fi
			 if ~ then ~ elif ~ else ~ fi
		 for loop
			 for variable in values
		 while loop
			 while expression
		 until loop
			 run while condition is false
			 until [ condition ]
		 Executing Shell
			 execute command in the new shell process
				 sh my.sh
					 sh : /bin/sh -> dash ,  minimal shell of bash for executing shell
					 execute command in the new shell process
				 my.sh
					 chmod +x
					 she bang
						 #! /bin/sh
						 #! /bin/env sh
			 execute command in the current shell process
				 source my.sh
					 source : execute command in the current shell process
				 . my.sh
					 . is alias for source
		 Shell Initialization
			 When the shell is invoked, startup files
			 system wide startup
				 /etc/profiles
					 set PATH, PS2
					 invoke /etc/profile.d/*.sh
				 /etc/profile.d/*.sh
					 custom changes
			 user-specific startup
				 ~/.bashrc
				 ~/.bash_aliases
					 invoked from ~/.bashrc
		  Shell Initialization
			 alias [-p]
				 list up defined alias
			 alias NAME=VALUE
				 define alias NAME for VALUE
			 ~/.bash_aliases
				 invoked from ~/.bashrc
			 23 Handy bash shell aliases
				 https://www.linuxtrainingacademy.com/23-handy-bash-shell-aliases-for-unix-linux-and-mac-os-x/
		 Process
			 An Instance of Program running
			 init (systemd) process
				 /sbin/init j /lib/systemd/systemd
				 First process after booting
				 Ancestor of all process
				 PID(Process Identifier) is1
					 ps –p 1
			 Parent Process
				 process that created child
			 Child Process
				 process that is created by parent
			 Deamon Process
				 not require controlling terminal
			 Orhpan Process
				 parent dies or get killed before the child
				 init process adopts
			 Zombie Process
				 child dies but parent does not fetch termination status
		 Searching Process
			 ps –ef | grep command
			 pgrep –l command
		 SIGNAL
			 Limited form of Inter Process Communication
			 Signals
				 kill -l
		 SIGNAL
			 Major Signals
			 sending signal
				 kill –signal target
		 Background Process
			 command &
				 run in background
			 ctrl + z
				 go stopped in background
			 jobs
				 list up background
				 run in background
			 fg [job_id]
				 run in foreground
		 nohup
			 run command ignoring hangup signals
			 nohup COMMAND &
		 Init and Systemd
			 First Process started during booting
			 continues running until the system is shut down
			 SysV style
				 Traditional init system from Unix
				 7 Run-levels
				 /etc/inittab
				 /etc/init.d/*
				 /etc/rc[0-6, S].d/*
			 systemd
				 Replacements for init
				 Since
					 Debian Jessie v8,  2015
					 RedHat v7.0, 2014
				 /lib/systemd/systemd
				 /lib/systemd/system/*.service
		 Run Level
			 mode of operation
			 7 run-levels in Linux SystemV init
		 Run Level
			 Systemd target
			 Mapping runlevels and systemd target
			 Determine current run level
				 runlevel
				 who –r
			 Change run level
				 sudo init [0-6]
			 shutdown
				 -P : power off
				 -h : power off
				 -H : halt, lowest state leaves it power on
				 -r : reboot
				 -c : cancel shutdown
				 -k : shudown warning to users
			 halt
				 -p : poweroff
			 poweroff : power off the machine
			 reboot : reboot the machine
			 wall : write a message to all user
		 Run Level
			 Setting Run Level
				 /lib/systemd/system/default.target
				 change symbolic link to
					 /lib/systemd/system/poweroff.target ( runlevel0 )
					 /lib/systemd/system/rescue.target ( runlevel1 )
					 /lib/systemd/system/multi-user.target (runlevel2, 3, 4)
					 /lib/systemd/system/graphical.target (runlevel5)
					 /lib/systemd/system/reboot.target (runlevel6)
		 Startup Service
			 Process that require autorun after booting
				 /etc/rc.local
					 System V Init Style Compatable
					 Invoked by /lib/system/system/rc-local.service
					 add command in the file
				 /lib/system/system/myd.service
					 Systemd Init Style
					 Create .service file
					 systemctl enable
					 systemctl start
					 systemctl stop
					 systemctl disable
			 Example shell, myd.sh
				 write time to ~/date.log every seconds
				 save as /home/pi/myd.sh
				 chmod +x myd.sh
		 Startup Service
			 Easy way : rc.local
				 open /etc/rc.local
				 add the command that invokes myd.sh before "exit 0"
					 su – pi –c '~/myd.sh' &
				 Reboot and Check the process
		 Startup Service
			 Add Service : myd.service
				 Create file /lib/systemd/system/myd.service
		 Startup Service
			 Add Service : myd.service
				 Enable and Start
				 Reboot and Check the Process
				 Stop and Disable
		 Getting User Information
			 Determine Current or User
				 id [ID]
				 who am i
			 Get all users logined
				 who
				 users
			 /etc/passwd
				 stores all user accounts information
		 Getting User Information
			 sudo passwd -aS
				 display all user accounts information
		 Getting User Information
			 sudo chage -l
				 display user accounts expiry information
		 Adding User Account
			 sudo adduser 
				 add a user or group to the system
		 Changing Password
			 passwd
				 own password
				 passwd must not be short
			 sudo passwd
				 someone else's password
				 passwd can be short
		 Creating Group
			 sudo groupadd 
				 add a group to the system
		 List up all Groups
			 cat /etc/group
		 Adding a user to an Group
			 sudo adduser  
		 Remove a user from group
			 sudo deluser  
		 Getting Super User authority
			 add user to sudo group
			 /etc/sudoers
			 sudo adduser  sudo
		 Sudo with No Password
			 make a file in /etc/sudoers.d
				 no contain '~' or '.'
		 Substitute User
			 su [-] 
				 - , -l, --login : login shell
					 Unset all variable and set again
					 Change Home directory
		 Become a Root
			 su – root
			 su -
		 Remove a existing group from system
			 sudo delgroup 
		 Remove a User from system
			 sudo deluser 
		 Enabling Root Account
			 NOTE : Not Recommended
			 Root Account is locked and not set password
				 Unlock
				 Set New Password
		 Enabling Root Account
			 NOTE : Not Recommended
			 Allow login through ssh
				 /etc/ssh/sshd_config
					 #PermitRootLogin prohibit-password  j PermitRootLogin yes
		 Disabling Root Account
			 Lock Account
			 Delete Password
				 sudo passwd –dl root
		 top, htop
			 Display Processes, cpu info, memory info
		 df
			 Show disk space usage
			 -k : kilo
			 -h : human readable
		 tar (tarballs)
			 make archive file
				 tar -cvf a.tar /abc /def aaa bbb
			 make archive with zip compression
				 tar -cvzf a.tar.gz /abc /def aaa bbb
			 extact archive file
				 tar –xvf a.tar
			 extract archive with zip compression
				 tar –xvzf a.tar.gz
		 Disk Utilities
			 lsblk
				 list block devices
			 fdisk
				 manipulate disk partition table
				 -l : list up
			 dd
				 data duplicate, convert and copy a file
				 dd bs=n if=input_file of=output_file
			 mount
				 -l : list up
				 mount [Device] [Mount_point]
			 umount
				 unmout file system
				 umount [Device_name]
		 APT(advanced package tool)
			 Tool system used to manage package in Debian line Linux
			 Package File
				 *.deb
			 Related Command
				 apt
				 apt-get
				 apt-cache
				 apt-config
				 aptitude
				 dpkg
			 Related Setting Files
				 /etc/apt/sources.list
				 /etc/apt/apt.conf
				 /etc/apt/preferences.d
		 apt
			 High level command using apt-get, apt-cache internally
			 Regular user version of apt-get/cache
				 apt list [package-name]
					 --installed
					 --upgradable
					 --all-version
				 apt search
				 apt show
				 apt install
				 apt remove
				 apt edit-sources : sources.list
				 apt update
				 apt upgrade
				 apt full-upgrade
		 apt-get
			 Tool used to handle APT package
				 apt-get update
					  Synchronize package list
					 Base on /etc/apt/sources.list
					 Need to run before upgrade or dist-upgrade
				 apt-get upgrade : Up-to-date all package installed in system
				 apt-get dist-upgrade : Change dependency of new version package
				 apt-get dselect-upgrade
				 apt-get install : Install given package
					 -y : auto yes
				 apt-get remove : Remove given package
				 apt-get purge : Delete and eliminate setting
				 apt-get source
				 apt-get download : Download in current directory
		 apt-cache
			 No system change in apt-cache
			 Offer package related information
			 apt-cache search [package-name]
				  Search package
			 apt-cache show [package-name]
				 See package information
		 dpkg
			 Tool need for package installation, building, deleting and managing
			 Tool for more general user than dpkg is aptitude
				 dpkg -r : Delete
				 dpkg -P : purge Delete
				 dpkg -l [package_name]:  Print install package list
		 Python
			 Guido Van Rossum(1956)
				 Created python(1989)in Amsterdam, Netherlands
				 Google (2005~2012)
				 Dropbox (2013 ~)
			 Named after a BBC comedy series “Monty Python’s Flying Circus”
			 Teaching Python instead of LISP to freshmen in MIT
			 Has two Versions : 2.x, 3.x
				 Not compartable
			 Interactive interpreted language
			 Independent platform
			 Dynamic type system
			 Rapid development
			 Simple and easy language
			 Object-oriented language
			 Multiple programming paradigms
			 Garbage Collection
		 Python Shell - Windows
			 IDLE
				 Menu > Python > IDEL
				 GUI-based interactive Python interpreter
				 Quit : Ctrl + D
			 Command
				 Python input at the Dos
				 Quit : Ctrl + Z Enter
		  Version to check
			 Terminal
			 Python shell
		 Basic Rule
			 A code starts with the first column
				 Exceptions-Python notes (#)
				 Use indentation to indicate code block
		 File Script - IDLE
			 File > New File
			 File > Save
				 ~/hello.py
			 Run > Run Module(F5)
		 File Script - Console
			 Creating a file with editor
			 Code-in
			 Running
		 File Script – Hashbang(shebang), Unix Only
			 #!
				 Hashbang, shebang, shabang, pund-bang, hash-pling
				 script interpreter directive
			 Adding Hashbang at the first line of file
				 #! /usr/bin/python
				 #! /usr/local/bin/python
				 #! /usr/bin/env python
			 Adding execution permission
		 PYTHONSTARTUP
			 a script to run whenever Python executed
			 https://docs.python.org/2/using/cmdline.html#environment-variables
			 startup.py
			 Set the File path to Environment variable
		 API Document
			 IDLE
				 Help > Python Docs(F1)
			 Online
				 Standard API : https://docs.python.org/2/library/
					 Built in Function : https://docs.python.org/2/library/functions.html
					 String Method : https://docs.python.org/2/library/stdtypes.html#string-methods
				 Global Modules : https://docs.python.org/2/py-modindex.html
				 External Modules : https://pypi.python.org/pypi
		  Help system
			 Interactive help system generates documentation on the console using help()
				 A line down : enter, down arrow, j
				 A line above : up arrow, k
				 A page down : space button, f
				 A page above : b
				 quit : q
		 Integrated Development Environment(IDE)
			 Eclipse + Pydev :
				 Slow pace
				 Available with other plug-ins
			 PyCharm
				 Rapid pace
				 Most widely used
				 Free or Charge
			 Other Editors for development
				 Sublime
				 Notepad++
				 brakets
		 Syntax
			 Case-sensitive
			 Use indentation instead of  parentheses
			 pass
				 If functions or conditional sentences are NOT included
			 Comments
				 # a single line comment
				 ‘’’(single quote * 3), “””(double quote*3) : multi-line comments
			 The End of sentence
				 Use a line break character instead of semicolon (;)
				 Use \(backlash) for line-breaking at the end of sentence
			 Korean Hangul Keyboard
				 # -*- coding:utf-8 -*-
					 Show the beginning of file
				 Insert Korean letters into a string literal
					 u ’Korean’
					 The 'u' in front of the string values
		 Keywords
			 import keyword
			 keyword.kwlist
		 Syntax
			 Comment
		 Variables
			 With no declaration
			 Data type dynamic binding according to a value of the quota
			 The naming convention
				 The first letter in English , under-score(_)
				 A number can be included from the second letter
				 Convention
					 Small letter_small letter
				 Eliminate duplication of the name of embedded module and function
			 del x : Delete variables
			 All variables are objects
				 Garbage Collection
			 Identifying an object
				 id()
					 UID(address) check
				 a is b
			 int.bit_length()
		 Variables
		 Data type
			 Number
				 int(integer)  : long in C, 32bit-min)
					 1, 100, 123
				 long(Python2 Only) : unlimited precision(as long as a memory allows), Use l, L
					 1L, 100L, 123L
				 float(real number) : double in C
					 3.14, 1.2
				 complex(complex number) : 64bit for each real/imaginary number, use j, J instead of i)
					 1 + 2j, 3j
			 boolean (subtype of integer)
				 True, False
			 str (Strings) : letter strings
				 "abc", 'hello'
				 Immutable sequence
			 None : No value
			 Built-in Data Structure
				 list[1,2,3], tuple(1,2,3), dict{1:’a’, 2:’b’}, set{1,2,3}
			 type()
				 Identify a dynamic type
		 Data type
		 Letter strings
			 ‘  ’, “ “
				 Use double quote mix with single quote
				 "hello", 'hello'
			 +
				 concatenation
			 *
				 repetition
			 ==
				 True when contexts are the same despite ID’s difference
			 in calculation (Membership check)
				 confirm to check the context
			 len(str)
				 A length of letter strings l
			 Format letters
				 %s: letter strings, %d: integer, %f: real number
			 Indexing : Turple
				 str[0], str[0:4]
			 Immutable Sequence
				 str[0] = 'h'  #Error
		 Letter strings
			 Main Methods
				 Startswith(s) : Does it start with -s?
				 Endswith(s) : Does it end with -s?
				 find(s) : index for s , if not -1
				 rfind(s) : find() from the end
				 count(s) : How often –s appears?
				 lstrip() : Delete the left side of blank
				 rstrip() : Delete the right side of blank
				 strip() : Delete either side of blank
				 isalpha() : Does it consist of English alphabets only?
				 isdigit() : Does it consist of numbers only?
				 isalnum() : Does it consist of English and numbers only?
				 replace(old, new[, count]) : replace old with new letter strings
				 format() : create a visual basic
					 {idx}
						 'my name is {0} and {1} years old'.format('Lee', 27)
					 {key}
						 'my name is {name} and {age} years old'.format(age=27, name='Lee')
		 Arithmetic operation
			 ‘abc’ + ‘def’  : ‘abcdef’
				 link together when adding letters
			 ‘10’ + 2, '10' – 2, '10' / 2  : error
				 Unable to add, subtract and divide between letters and numbers
			 ‘abc’ * 3  : able to multiply letters and numbers
				 ‘abcabcabc’
			 2 ** 3 : 8
				 square
			 7 / 4 :  1
				 Integer as a result of integer calculation(Python 2)
				 Real number as a result of real number calculation(Python3)
			 7 % 4 : 3
				 Residue check
				 divmod(7, 4) : compute quotient and remainder
			 7 / 4.0 : 1.75
				 Real number as a result of real number calculation
			 7 // 4.0   : 1.0
				 emission of fraction after a decimal point
			 (2 + 3j) + (3 + 2j) : 5 +5j
				 Complex number calculation
			 i++, i--, ++i, --i : error
				 i+=1, i-=1
		  Operator
		 Comparison operator
			 a == b
			 a != b
			 a  >  b
			 a >= b
			 a < b
			 a<=b
		 Logical operator
			 Unable to use &&, ||, !
			 a and b
			 a or b
			 not a
			 a in b
			 a not in b
		 Comparison & Logical operator
		 Bitwise operator
			 ~ :   ~5
				 Bit reversal (One’s complement)
			 << :  3 << 2
				 Left Shift, each bit is shifted to the left
				 left bit is dropped
				 Right bit to be filled by 0 s (zeros)
			 >> : 4 >> 1
				 Right Shift, each bit is shifted to the right
				 right bit is dropped
				 Left bit to be filled with the last bit on the left
			 & :  3 & 2
				 Bitwise AND
			 | : 3 | 8
				 Bitwise OR
			 ^ : 15 ^ 6
				 Bitwise XOR
		 Bitwise operator
		 Type conversion
			 to convert integer
				 int(“10”)
				 int(True)
				 long("1234")
			 to convert real numbers/complex numbers
				 float(‘3.14’)
				 float(123)
				 complex("3+5j") , blanks are Not allowed
			 to convert letters in a string str(10)
				 ‘%s’ %10
		 Console Input and Output
			 Python 2
				 input( [prompt] )
					 evaluate user input
					 easy number input
					 enable string input if enclosed in double quotes
				 raw_input( [prompt] )
					 return user input for string
					 number input required for conversion
				 print exp1, exp2…
					 Console output
					 Tuples
			 Python 3
				 input([Prompt])
					 Same with of raw_input python2 (eliminate raw_input )
				 print( exp1, exp2...)
					 Console output
					 A function, not a command
		 If-else Condition
			 if  :
			 if  :
			 if  :
		 Practice – credit program
			 Input : score ( 0 ~100)
			 Output : credit (A : ≥ 90, B : ≥ 80, C : ≥ 70, D: ≥ 60, F : < 60
			 Examples
		 Repetition Statements - for
			 for x in […] :
			 Should be Sequence Type
			 The function of range()
				 xrange() : python2
				 range() : python3
		 Practice - Double dice
			 Roll two six-sided dice ten times
			 Sum of two dice output
				 7
				 11
				 Same spot
			  Random number
				 import random
				 random.randint(start, end)
		 Repetition Statements - while
			 while  :
		 Practice – Guess the number
			 Random number( 1 ~ 100)
			 insert number you guess
			 Higher/lower output
			 Repeat untill correct answer
			 Examples
		 Practice – Guess the number
		 List
			 Similar to a simple Array language
			 The most frequently used
			 Mutable Sequence Type
				 a group of sequence data types
				 Indexing, Slicing, Concatenation, Iteration
				 Changeable, Resizing
			 Syntax
				 my_list = [1,2,3,4]
				 my_list[0] : 1
				 my_list[-1] :  4
					 first from the end
				 my_list[1:3] : [2, 3]
				 my_list[:3] : [1,2,3]
				 my_list[1:] : [2,3,4]
				 my_list[ : ] : [1,2,3,4]
				 my_list[1 : :2] : [2,4]
				 my_list[::2] : [1,3]
				 my_list * 2 : [1,2,3,4,1,2,3,4]
				 my_list + [10,20] : [1,2,3,4,10,20]
				 my_list[1] = 5 : [1,5,3,4]
			 Method
				 append : add at the end
				 insert :
				 index : search for elements
				 count : count elements
				 sort  :
				 reverse :
				 remove :
				 pop : remove after getting the last item in the list
				 extend : add list
		 List
			 Functions
				 range( stop), xrange()
				 range(start, stop [, step])
					 Create a sequence integer list
					 start default : 0
					 the last item is stop – 1
					 step default : 1
				 len(list)
					 sizing
				 list() : type conversion
		 Tuple
			 Read-only List, often use in argument, return value of function
				 Immutable
				 No methods
			 Sequnce Type
				 Indexing, Slicing, Iteration
			 Syntax
				 my_tup = 1,2,3,4
				 my_tup = (1,2,3,4)
				 my_tup = (1,)
					 Comma is needed when there is an element
				 my_tup[1] : 2
				 my_tup2] = 5 : Error
				 a,b,c,d = my_tup
				 a,b,c,d = 1,2,3,4
				 a,b = c, d
			 Function
				 tuple()
					 Type conversion
				 len()
		 Set
			 Set data type
				 No sequence
				 No duplication
			 Syntax
				 my_set = {1,2,3,4,5}
				 my_set = set([1,2,3,4,5])
			 Methods
				 s1.add(el) : add an element
				 s1.update([1,2,3]):add multiple elements
				 s1.discard(el),  s1.remove(el) : remove  an element
				 s1.clear() : clear all elements
				 s1.union(s2) , s1 | s2 :
				 s1.intersection(s2) , s1 & s2:
				 s1.difference(s2) , s1 – s2 :
				 s1.symmetric_difference(s2), s1^s2 :
				 s1.issubset(s2), s1 <= s2 : s1 is a  subset of s2
				 s1.issuperset(s2), s1 >= s2 : s1 is a  superset of s2
		 Dictionary
			 Mapping Type
				 Key : value
				 Key is Set
			 Syntax
				 dict()
				 my_dic = {‘a’ : 1, ‘b’:2}
				 my_dic[‘a’]  : 1
				 my_dic[‘b’] = 5
					 {‘a’:1, ‘b’: 5}
				 my_dic['c'] = 6
					 {'a':1, 'b' : 5, 'c':6 }
			 Main Methods
				 dic.get(key [, default]) : if given key exists, returns its value.
				                                         Otherwise, it returns to the given default value.
				 dic.pop(key) : remove the element with given key from dictionary and return its value
				 dic.keys() : return a view object that displays a list of all the keys
				 dic.values() : return a view object that displays a list of all values in a given dictionary
				 dic.items() : return a view object that displays a list of dictionary's (key, value) tuple pairs
				 dic.clear() : remove all items from the dictionary
		 Comprehensions
			 List ,Set, Dictionary
				 Apply function to each element of the matrix of lists and return results in List, Set, Dict
				 [ expression for ~in if condition]
			 Application of arithmetic coding
				 S = {x² : x in {0 ... 9}}
				 V = (1, 2, 4, 8, ..., 2¹²)
				 M = {x | x in S and x even}
			 Comprehension
				 s= [ x**2 for x in range(10)]
				 v= [ 2**x for x in range(13)]
				 m = [x for x in s if x%2 == 0]
		 Function
			 Subroutine
			 A series of code to repeatedly use
			 Syntax
			 Return None Type if return statements  not present
			 Main Declaration Type
				 def fn():
				 def fn(a, b):
				 def fn(*args):
					 Tuple type
				 def fn(num=0)
					 default value
				 def fn(**kwargs)
					 Dictionary type
		 Function
		 Function
		 Namespace
			 LGB(Local, Global, Built-in)
			 Access in Function
				 confusion between local and global variables
				 Global Variable :Accessed by any statement in the entire program
				 Variables are declared inside and outside a function
			 dir(__builtins__) : Built-in name space
		 Lambda
			 Anonymous Inline Function
			 No return statement
			 Syntax
		 Practice – calculator
			 When you put the 4 fundamental arithmetic operations, you can get an output
			 Get the remainder using of the given code
				 plus(a,b), minus(a,b), multiply(a,b), divide(a,b)
				 str2num(str_val) : int | float
			 Examples
			 Code provided
		 Practice – calculator
			 Implemented code
		 Practice - Hangman
			 Figure out a word
			 Given 6 words
			 input a letter or word that a user guess
			 Show as ---
			 Show a part in alphabet if correct
			 14 chances in total
		 Practice - Hangman
		 Practice - Hangman
		 Module, Package
			 module
				 A piece of software that has a specific functionality
				 *.py file
			 package
				 A unit collecting modules that have a similar functionality
				 *.py a directory collecting files
				 __init__.py file required(Python 2 Only)
			 How to use modules and packages
				 import random
				 imoprt random as r
				 from random import randint
				 from random import *
		 custom module
		 custom package
			 A directory including modules
			 __init__.py file included
			 Choose the latter imported name if duplicated
		 custom package
			 Custom module same with average API
		 Top Level module
			 A module used at the beginning of execution
			 Built-in module: The value of __name__ is '__main__'
				 Use the given module name if it’s not Top Level
				 if __name == '__main__'
		 __init__.py
			 Package should have  __init__.py file
			 Normally empty file
			 Specification of modules in response to import *
				 __all__ = [ 'module_name-1' , 'module_name-2' … 'module_name-3']
		 __init__.py
		 Module Path
			 A location where Python search for Module
				 No separate *.py file
				 sys.builtin_module_names
					 PYTHON_HOME/site-packages
		 Class
			 A system that can classify the same type, DataType
			 A essential template to create objects that have the same structure(functions, variables)
		  Object
			 Unique things generated by Class
			 Share unique function with the value(variables)
		 Practice-Turtle Class
		 The definition of Class
			 Syntax
			 The name of class starts with a capital letter
		  Object generation and application
			 Syntax
		 Instance check
			 type(obj)
			 obj.__class__.__name__
			 isinstance(obj, Class)
		 Class definition and application
		 __init__ Method
			 Automatically called when you call it to create
			 Objects are initialized
		 Class variable VS Instance variable
			 class variable : variables generated in Class
				 Create a variable in Class
				 Use class name to access
				 Instance access
					 if instance variable of the same name is not present : class variables access
					 if instance variable of the same name is present : instance variables access
			 instance variable : Variables generated through self in method
				 Independent variables are created in each object
				 Instance access
				 Inaccessible with the name of Class, Error
		 Class / Instance variable
		 Static method
			 Method irrelevant to class or instance
			 Call it through Class
			 Able to call it through Instance, not recommended
			 Use @staticmethod Decorator
		 Class method
			 Method for class-related work
			 Irrelevant to Instance
			 Deliver class reference value when you call
			 Use @classmethod Decorator
		 Instance method
			 Method for  Instance-related work
			 most of methods
			 Deliver class reference value when you call
		 Encapsulation
			 Block access of instance variables from outside
			 Access through a function
			 The name of variables
				 highlight 2 prefixes
				 only one suffix is allowed to highlight but is not private for a suffix of double line
		 Inheritance
			 Similar class with the existing one
			 Extension of class functionality
			 Reuse code
			 Syntax
			 or
		 Inheritance
		 Method Overriding
			 Redefine the inherited method from Base class
			 Name it as the same with the method
			 Irrelevant to parameter type
		 Multiple Inheritance
			 Designate multiple Base classes
			 Same method name increases ambiguity
				 prioritize class which was put at the front
		 Abstract Class
			 Unimplemented class
			 Impossible to generate objects
			 abc.@abstractmethod included
			 __metaclass__=abc.ABCMeta
		 Hidden methods
			 __call__()
				 A response when you call function method from instance method
				 Application to @decorator
				 Hooking into function calls
			 __iter__(), next()
				 Application to Iteration through for ~in
				 __iter__
					 Return object that has next() in for statements e
					 __next__()  : renamed in python 3.x
				 next
					 Call for every for statements
					 Raise StopIteration after repeating
		 __call__ , Decorator
		 __iter__ , Iterator
		 Generator, yield
			 Able to use for~in statements without __iter__
			 Replace with yield statements
			 Reentrancy function
		 Exception
			 Error while in operation
			 The program abnormally end If left untreated
			 try :
				 statements that exceptions expected
				 Jump over the except block if exceptions occur
			 except Exception:
				 Execution if certain exceptions occur
			 except :
				 Execution regardless of exceptions
			 else :
				 Execution unless exceptions occur
			 finally
				 Execution regardless of exceptions
		 Exception occurance
			 rase Exceptions
		 Exception information
			 sys.excinfo()
				 Kinds of exception, value, trackback
		 Exception handling
		 Built-in exceptions
			 Exception
				 Root class of all exceptions
				 No forcible regulation of user definition exception class
			 StandardError
				 Base class of all built-in exceptions except Systemexit
			 Arithmetic Error
				 Base class of OverflowError, ZeroDivisionError, FloatingPointError
			 LookupError
				 Base class of IndexError, KeyError
			 EnvironmentError
				 Base class of external exceptions occurance(IOError, OSError)
		 Custom Exception
		 File read
			 f = open(file_name)
			 f.read()
			 f.close()
		 File write
			 f = open(file_name, 'w')
			 f.write(‘content’)
			 f.close()
		 open(name, mode, bufferring)
			 name : file name
			 mode
				 r : read mode
				 w : write mode
				 a : append mode
			 bufferring
				 0 : no use of buffer
				 1 : system default buffer use
				 >1 : buffer use of designated size
		 File read / write
		 Context manager
			 Use with ~ as statement
			 Resource management(close()) automatically call functions
			 Automatically call when entering __enter__ : with statement
				 Return reference value in as statements
			 Automatically call when leaving __exit__ : with statement
				 Implementation of function call such as close()
		 File with ~ as
			 Able to omit close() function call
		 Read by line
			 f = open(name)
			 f.readline()
			 f.readlines()
			 f.close()
		 Write by line
			 f = open(name, 'w')
			 f.writelines()
			 f.close()
		 Thread
			 A small process inside of a process
			 Parallel transaction
			 asynchronous processing
			 Easy for memory share and control comparing to parallel process
		 Three ways
			 thread module (low level)
				 thread.start_new_thread(fn_name, (x,y,…))
			 threading module (high level)
				 Direct generation , Simple
					 th = threading.Thread(target=fn_name, args=(x,y,…))
					 th.start()
				 Inherited implementation, Detail Control
					 class MyThread(threading.Thread)
						 def fun():
					 th = MyThread()
					 th.start()
		 Thread module (low level)
		 Threadding module
			 Direct generation
			 Inherited implementation
		 Thread control
			 terminate a thread when main ends
			 No specific functions to kill thread
			 Decide whether or not maintain work through state variables of  thread
		 Timer
			 Function call after given period of time
			 threading.Timer(delay, fn, args=[])
		 time module
			 time() : return present time
			 localtime() : local time
			 gmtime() : Greenwich Mean Time
			 strftime() : Format time as a string
				 %Y :Year, %m: month, %d : date, %H:Hours, %M:Minutes, %S:Seconds
			 delay(sec) : delay operation
		 datetime module
			 date
				 date(year, month, day)
				 today()
				 weekday()
				 year, month, day
			 time
				 time(hour, minute, second, microsecond)
				 strftime(format)
				 hour, minute, second, microsecond
			 datetime
				 datetime(year, month, day, hour, minute, second, microsecond)
				 today()
				 date()
				 time()
				 year, month, day, hour, minute, second, microsecond
		 time, datetime
		 Socket as a server
			 soc = socket(AF_INET, SOCK_STREAM)
				 generate socket stream
			 soc.setsockopt(SOL_SOCKET, SO_REUSEADDR,1)
				 Set closed socket reuse
			 soc.bind( (‘ ‘, 1234) )
				 Socket binkidng
			 soc.listen(5)
				 Maximum listener : 5
			 conn, addr = soc.accept()
				 Beginning of waiting
			 msg = conn.recv(1024),
				 msg.decode('utf-8') : Python3
			 conn.send(‘content’), conn.send(b‘content’), conn.send(‘content’.encode('utf-8')
			 conn.close()
			 soc.close()
		 Socket as a Client
			 soc = socket(AF_INET, SOCK_STREAM)
				 Create a stream socket
			 soc.connect( (host, port) )
			 msg = soc.recv(1024) : Python2
			 msg = soc.recv(1024).decode('utf-8') : Python3
				 transmission
			 soc.send(‘content’) : Python2
			 soc.send(b‘content’): Python3
			 soc.send(‘content’.encode('utf-8')) Python3
				 reception
			 soc.close()
				 Socket close
		 Socket by server
			 Server Execution
			 putty(telnet) localhost 1234 access
		 Socket by Client
		 Socket by server using thread
		 Socket by Client using thread
		 Web Architecture
		 Client/Server Timeline
		 Hyper-Text Transfer Protocol over TCP/IP
		 History
			 HTTP 0.9 : No Spec Sheet
			 HTTP 1.0 :
				 Fix : 1996’ IETF RFC 1945
				 Difference between spec and implementation
				 Added Header, GET Method
			 HTTP 1.1 :
				 Fix : 1997’ IEFT RFC 2068,
				 Rev. 1999’, RFC 2616(Current Version)
				 Cache Control, connection keep
				 http://tools.ietf.org/html/rfc2616
		 Feature
			 Connectionless
			 Stateless
			 Request and Response
		 HTTP Request Structure
		 Request Methods
		 HTTP Request Example
		 HTTP Response Structure
		 HTTP Response Example
		 Response Status Code
		 Response Status Code
		 Multipurpose Internet Media Extensions Type
		 Internet Media Type
		 Content-type
		 Syntax
		 Example
		 Socket Webserver
		 SimpleHTTPServer
			 List up current directory; exemplary class running function
		 BaseHTTPServer
			 Compose custom server inheriting BaseHTTPReuqestHandler
		 WSGI
			 Web Server Gateway Interfacce
			 CGI standard for Python (PEP-333)
		 Http Client
		 Flask
			 http://flask.pocoo.org/
			 Micro framework based on WSGI
			 Armin Ronacher, Austrian(http://lucumr.pocoo.org/)
			 Light framework
			 Able to expand as needed
			 route function
			 Jinja Template
		 Installation
			 pip install flask
		 URL Routing
			 Register individual function handler according to requested URL/Method
		 URL Routing Parameter
			 Sub path of specific URL
			 REST Style
			
			
			
			
			
			
			
			
			
			
			
			
			
		 Static File
			 Simple file service not registered in route
			
			
		 Parameter Collection
			 GET Method
				 from flask import request
				 request.args.get(‘name’)
				 request.values[‘name’]
		 Parameter Collection
			 POST Method
				 from flask import request
				 request.form[‘name’]
				 request.values[‘name’]
		 Parameter Collection
			 POST Method
			 static/form.html
		 Template
			 Jinja2 (http://jinja.pocoo.org/docs/dev/)
				 Basic Tmeplet Engine
				 Data composition to static HTML file
			 render_template()
		 Template
			 templates/test.html
		 Session
			 session.secret_key
		 Flask-Socket.IO
			 https://flask-socketio.readthedocs.io/
			 Socket.io that can be used with Flask
				 http://socket.io/
			 Installation
				 sudo pip install flask-socketio
				 sudo apt-get install python-dev
				 sudo pip install gevent or pip install eventlet
			 Main code
				 from flask_socketio import SocketIO, send
				 socketio = SocketIO(app)
				 socketio.run(app)
				 @socketio.on(‘message’)
				 send(‘message’, broadcast=True)
				 socket.send(‘message’) : Use externally
				 emit(‘event name’, ‘message’,  broadcast=True)
		 websocket.py
		 static/websocket.html
		 static/websocket.html 
		 static/websocket.html 
		 GPIO
			 General Purpose Input Output
			 Hava no predefined purpose, unused by default
			 Some pin has Alternative functionality (e.g. Tx, Rx, CLK etc.)
			 Can be configured to be INPUT or OUTPUT
			 Input values are 1(High) or 0(Low)
				 Tri-state : Hi-Z
				 Pull-up or Pull-down
			 Output values are 1(High) or 0(Low)
				 High : 3.3v
				 Low : GND
		 Raspberry Pi 3 GPIO
			 40 physical pins
			 26 available GPIO Port
				 02 ~ 27
			 2 Types Numbering
				 BCM SoC
				 Board Physical
		 Raspberry Pi GPIO Pin Header
			 Pin header mapping
		 4 Ways to Control GPIO
			 Low Level C programming
			 Highest Performance, Lowest productivity
			 Dependency to specific H/W board
			 3rd party C Library
				 Easy way C programming
				 Dependency to specific H/W board and Library
				 /dev/class/gpio
				 Command line or Linux System call Programming
				 Low Hardware Dependency, Cross H/W with Linux
			 Language(Script) Bindings
				 Python, Java, NodeJs(Javascript), Perl, Scratch, etc…
				 Easy Programming
				 Lowest Performance, Highest Productivity
				 No H/W, Platform(OS) Dependency, Cross Platform
		 Direct Register Access
			 Access Register of BCM 28xx Directly
				 Memory GPIO address mapping using mmap() function
				 /dev/mem  : Root privilege needed, available for GPIO, I2C, SPI etc.
				 /dev/gpiomem  : Rootless, GPIO only
			 Board/Hardware Dependency
			 Needed to reference Soc Datasheet
				 https://www.raspberrypi.org/wp-content/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
		 Direct Register Access  gpio_register.c<1/4>
		 Direct Register Access gpio_register.c<2/4>
		 Direct Register Access gpio_register.c<3/4>
		 Direct Register Access gpio_register.c <4/4>
		 3rd party C Library
			 Provide complex register access as an easy C function
			 Dependency to H/W and Library
			 Wiring Pi :
				 http://wiringpi.com/ (Gordon)
				 Arduino wiring-like  Library for Raspberry Pi
			 BCM2835
				 http://www.airspayce.com/mikem/bcm2835/ (Mike McCauley)
		 Wiring-Pi
			 Installation
				 Installed by default on Jessie or later.
					 Not required on most Rasbian recently
				 sudo apt-get install git-core
				 Git clone git://git.drogon.net/wiringPi
				 Cd wiringPi
				 ./build
			 Console Command line
				 can use "gpio" command after installing WiringPi
				 -g options : GPIO pin numbering
		  Wiring Pi Library gpio_wiringpi.c <1/1>
		 BCM2835
			 Installation
				 wget  http://www.airspayce.com/mikem/bcm2835/bcm2835-1.50.tar.gz
				 tar zxvf bcm2835-1.50.tar.gz
				  cd bcm2835-1.50/
				 ./configure
				 make
				 sudo make check
				 sudo make install
		 BCM2835 Library gpio_bcm2835.c <1/1>
		 Sysfs
			 Linux Kernel 2.6+
			 Special File System
			 Includes drivers for GPIO control
			 C Programming using System calls
			 Indepentent of board type, Available on any Linux OS
			 Console  command
		  Sysfs C Program – gpio_sysfs.c <1/2>
		 Sysfs C Program - gpio_sysfs.c <2/2>
		 Sysfs Python Program – gpio_sysfs.py <1/2>
		  Sysfs Python Program - gpio_sysfs.py <2/2>
		 Java  Binding
			 JDK(Java Development Kit) Default Installed on Raspberry Pi.
				 java –version
				 javac –version
			 Pi4j (http://pi4j.com)
				 Java I/O library for Raspberry Pi
				 Dependency on WiringPi
				 Pin Mapping with WiringPi
				 Installation
					 $ curl –s get.pi4j.com | sudo bash
		 Java Binding – GPIO_Pi4j <1/1>
		 Python GPIO Modules
			 Rpi.GPIO
				 https://pypi.python.org/pypi/RPi.GPIO
				 https://sourceforge.net/projects/raspberry-gpio-python/ (Ben Croston)
				 Installed by default in Raspberry Pi
				 Most popular way in Raspberry Pi
				 Wrapping  way of Direct Register Access
				 GPIO and Software PWM support only
				 H/W PWM, SPI, I2C, UART not support
		 Rpi.GPIO  basic API
			 import Rpi.GPIO as GPIO
				 Module import
			 GPIO.setmode(GPIO.BCM or GPIO.BOARD)
				 GPIO.BCM : Pin Number that Broadcom Soc  defined
				 GPIO.BOARD : Pysical Raspberry-Pi board  Pin number
			 GPIO.setup(channel, direction[, intial=state] )
				 channel : GPIO Pin number
				 direction :  GPIO.IN, GPIO.OUT
				 state : GPIO.HIGH, GPIO.LOW
			 GPIO.setup(channel, GPIO.IN [, pull_up_down=pud])
				 pud = GPIO.PUD_UP, GPIO.PUD_DOWN
			 GPIO.input(channel)
			 GPIO.output(channel, state)
			 GPIO.cleanup()
				 Release Resource before exiting
			 https://sourceforge.net/p/raspberry-gpio-python/wiki/Examples/
		 Python Rpi.GPIO  - gpio_python.py
		 Python GPIO Modules
			 WiringPi-Python
				 https://github.com/WiringPi/WiringPi-Python
				 wrapper of WringPi written in C
				 Arduino style Code
				 Support all H/W functions such as GPIO, Serial, SPI, I2C, Hardware PWM
				 Wiringi-Pi Library dependency
					 Wiring-Pi build/install required
				 Installation
					 sudo pip3 install wiringpi
					 or
						 cd ~
						 git clone --recursive https://github.com/WiringPi/WiringPi-Python.git
						 sudo apt-get install python-dev python-setuptools swig
						 cd WiringPi-Python
						 ./build.sh
		 Python WiringPi-Python – gpio_wiringpi.py
		 NodeJs GPIO Modules
			 Finding Good module
				 https://www.npmjs.com/
				 http://node-modules.com/
				 https://nodejsmodules.org/
				 http://npmsearch.com/
			 Major Modules
				 onoff
				 Johnny-Five
				 WiringPi-Node
			 Minor or No more maintaned
				 gpio
				 rpi-gpio
				 pigpio
				 rpio
				 mmm-gpio
				 pi-gpio
		 NodeJs GPIO Modules
			 onoff
				 https://github.com/fivdi/onoff
				 most popular
				 Synchronous, Asynchronous function
				 Linux Sys-fs is used internally
				 epoll is used to interrupt mode, callback
				 Install
					 npm install onoff
				 Basic API
					 var Gpio = require('onoff').Gpio
					 Gpio(gpio, direction)
					 read(callback), readSync()
					 write(value, callback), writeSync(value)
					 watch(callback), unwatch(callback), unwatchAll()
					 direction(), getDirection(direction)
					 unexport()
		 NodeJs onoff module – gpio_onoff.js
		 NodeJs GPIO Modules
			 Johnny-Five
				 http://johnny-five.io/
				 JavaScript Robotics & IoT Platform
				 Abstractions of many types of H/W boards
					 All API of H/W is the same
					 Arduino, RaspberryPi, BeagleBone, Intel Edison etc.
				 http://johnny-five.io/platform-support/#raspberry-pi-3-model-b
					 raspi-io module is used internally
					 https://github.com/nebrius/raspi-io
				 Installation
					 npm install raspi-io
					 npm install johnny-five
		  NodeJs Johnny-five module – gpio_johnnyfive.js
		 NodeJs GPIO Modules
			 WiringPi-Node
				 https://github.com/WiringPi/WiringPi-Node
				 Node.js bindings to wiringPi
				 Faster than others
				 Install
					 npm install wiring-pi
				 Core functions
					 var wpi = require('wiring-pi')
					 wiringPiSetup(), wiringPiSetupGpio(), wiringPiSetupPhys(), wiringPiSetupSys(), setup(mode)
					 pinMode(pin, mode)
					 digitalRead(pin)
					 digitalWrite(pin, state)
		 LED Blink
			 LED Blink
			 Part
				 LED(Light Emitting Diode)
					 Short Leg: Cathode, Negative( - )
					 Long Leg: Anode, Positive( + )
					 The head of cathode is cut.
				 Resister
					 Block flow of electric current
					 Voltage, decrease electric current
					 No electrode
					 Unit: Ω(ohm)
			 Connect Circuit
				 LED Long leg: GPIO18 + Resister
				 LED Short leg: GND
		 Calculating Resistor Value
			 LED Voltage, Check electric current
				 Data sheet
				 5mm red as base
				 Electric Current 20mA
				 Voltage approx. 1.8V~2.2V
			 Ohm’s kaw
				 V = I * R
				 R = V / I
				 (Supply Voltage – LED Voltage) / Electric Current
				 (3.3 – 2) / 0.02 = 65
				 Use resistor value most close to 65: 100Ω (220Ω)
		  Reading Resistor
			 In the past, it was difficult to print #
			 4 or 5 color band
			 Gold or silver to right
			 4 Color band:
				 3rd # is multiplier (# of 0)
				 4th # is margin of error
			 5 Color band:
				 4th number is multiplier (# of 0)
				 5th # is margin of error
			 e.g
				  Brown(1),Black(0),Orange(103),Gold
					 10,000Ω = 10KΩ, ±5%
			 Red(2),Red(2),Brown(101),Gold
				 220Ω, ±5%
			 Orange(3),Orange(3),Brown(101),Gold
				 330Ω, ±5%
			 Brown(1),Black(0),Green(105),Gold
				 1,000,000Ω = 1MΩ ,±1%
		 Bread Board
			 Prototype before making PCB
			 No need to weld
			 Able to assemble and disassemble
			 Connect to the same row
			 Left and right vertical line for power(Bus)
			 Center 5 spots for part (IC)
		 Composing LED Blink Circuit
		  Led onoff Code
			 Python Rpi.GPIO module  - digital_out.py
		 Led onoff Code
			 Python WiringPi module  - digital_out_wpi.py
		  Relay Switch
			 Turn on/off 220V(110V) Home Appliance
			 Home appliances other than 5v power control
			 Necessary parts
				 Replay Switch
					 IN, 5V, GND
				 Static semiconductor relay
					 IN, GND
				 220V Plug fe/male
		 Composition of Relay Switch Circuit
		 Composition of Relay Switch Circuit
		 Relay Switch Code
			 Same as LED Blink
		 Transistor
			 Transistor = Trans + Resistor
			 Semiconductor Device
			 3 Socket: C(Collector), B(Base), E(Emitter)
			 Change internal resistor value according to base
			     socket electric current (voltage)
			 Use for amplifying circuit and switching circuit
				 Accelerator pedal for automobile
				 Run if base voltage is higher than 2m
			 PNP
				 Run if base voltage is lower than 2m (0.6v)
		 Transistor Switch
			 2n2222
				 Commonly used NPN mating type
				 Controls electric current not voltage
				 Protect transistor using resistance
			 Circuit composition
				 USB Connector Vcc – R-PI 5V
				 USB Connector GND – Collector
				 R-PI GPIO18 – Base(220Ohm)
				 R-PI GND - Emitter
		 Transistor Switch Circuit Composition
		 Transistor Switch Code
			 Same as LED Blink
		 Push Button Switch Input
			 Turn on/off LED with button switch
			 Button Switch
				 Two legs are connected
				 Works with only two of four legs connected
			 Connect Circuit
				 #13 – LED – GND
				 Pull-down resistance
					 5V – button – 10k resistance – GND
					 Button -  Digital #7
				 Pull-up resistance
					 5V – 10k resistance – button – Digital #7
					 Button – GND
		 Pull-Up, Pull-Down Resistor
			 Floating Condition
				 Condition unknown while switch is open
				 Weak on noise like surrounding pin voltage, electric statics
				 Solve by connecting 0V(GND) or Vcc (5V) while switch is open
				 When Vcc and GND is directly connected overflowing electric current causes short-circuit
				 Generally, use 10KΩ resistor to solve the issue
				 Pull up when resistor is connected to Vcc and pull down when resistor is connected to GND
		 Pull Up, Pull Down Resistor
			 Connect GND without resistor
				 Fire
		 Push Button Switch Circuit (Pull-up Resistor)
		 Push Button Switch Circuit (Pull-down Resistor)
		 Switch Input
			 Python Rpi.GPIO module  - digital_input.py
		 Switch Input
			 Python WiringPi module  - digital_input_wpi.py
		  Internal Pull-up/down (Push Button Switch)
			 Pull up resistor is supplied internally
			  GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_UP)
			  GPIO.setup(pin, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
		 Switch Internal Pull-Up/Down
			 Python Rpi.GPIO module – digital_input_pud.py
			 Python WiringPi module – digital_input_pud_wpi.py
		 Magnetic Door Switch
			 Sense door open
			 Switch working by two magnetic closing and opening
			 Necessary parts
				 Magnetic door switch
				 10KΩ resistor
			 Use same circuit and sketch as Push Button
		  Interrupt / Edge detecting
			 Polling
				 Check pin value and condition periodically
				 Adjust period with delay() function
				 Halt all program while delay()
				 Waste unnecessary CPU
				 When it does not fit on the period, input is omitted
			 Interrupt
				 When condition is met, call-back designated function (ISR)
				 Runs separately from delay() period
		 Interrupt – RPi.GPIO
			 Edge Type
			 GPIO.RISING
				 GPIO.FALLING
				 GPIO.BOTH
			 wait_for_edge(pin, type)
			 add_event_detect(pin, type [, callback=fn,  boucetime=ms])
		  Interrupt / Edge detecting
			 Python Rpi.GPIO module – interrupt.py
		 Interrupt / Edge detecting
			 Python WiringPi module – interrupt_wpi.py
		  LDR (Light Dependent Resistor)
			 조광센서
			 양음극 없음
			 가변저항, 빛에 따라 저항값 변화
				 밝으면 저항 감소, 어두우면 저항 증가
				  10Lux : 20 ~ 50kΩ
				 0Lux : 2MΩ
			 회로
				 주변 환경에 따라 풀다운 저항 변경(10K~1M)
				 가변적인 전압의 특정 값 이상/이하 입력
				 Analog 신호를 Digital로 인식
		 LDR (조도센서) 회로구성
		  LDR(조도센서) Code
			 Python Rpi.GPIO module – ldr.py
		 LDR(조도센서) Code
			 Python WiringPi module – ldr_wpi.py
		  적외선 센서(Infrared Sensor)
			 적외선 발생기(IRED)
				 Infrared Emitting Diode
				 LED 모양
				 일반적으로 리모콘 끝 부분에 장착
				 육안으로 빛을 볼 수 없슴
					 카메라 뷰파인더로 확인 가능
				 동작 전류 : 100mA
				 동작 전압 : 1.3v ~ 1.7v
				 필요  저항 : 5v 일때 35Ω
					 (5 – 1.5)v / 0.1A = 35
		 적외선 센서(Infrared Sensor)
			 적외선 수신기(Photo Transistor)
				 적외선 수신에 따른 트랜지스터
				 적외선 값에 따라 Collector-Emitter 저항 변화
				 Pull-down 저항 1MΩ
		 적외선 센서 회로구성
		 적외선 센서 Code
			 Python Rpi.GPIO module -  ir.py
		  적외선 센서 Code
			 Python wiringpi module -  ir_wpi.py
		 인체 동작 감지
			 사람의 움직임 유무 감지
			 인체 온도 36.5o 적외선 파장 감지
			 필요 부품
				 Passive Infrared, PIR 센서
					 1 : Out
					 2: Vcc
					 3: GND
		 PIR 센서 Code
			 Python WiringPi module  - pir_wpi.py
		 PIR 센서 Code
			 Python Rpi.GPIO module  - pir.py
		 Touch Sensor
			 인체의 전류 감지
			 3핀
				 Red : Vcc (3~5V)
				 Green : Data Out
				 Black : GND
			 단순한 Digital Input
		 Touch Sensor
			 Python Rpi.GPIO module  - toche.py
			 Python WiringPi module  - touch_wpi.py
		 Analog Out
			 PWM( Pulse Width Modulation) 펄스 폭 변조
				 지정된 주파수의 펄스의 폭을 조절하여 아날로그 신호로 사용
				 주파수(Frequency) : Hz, 1초에 일어날 펄스의 갯수
				 주기(Period) : 한 펄스의 지속 시간
				 Pulse Width : 하나의 Period에서 활성화된 기간
				 Duty Cycle : 한 주기 내에서 HIGH 상태 시간 비율
		  Raspberry-Pi PWM
			 Hardware PWM : BCM2835 SoC
				 레지스터 ALT0
					 GPIO12,13 – PWM0, PWM1
				 레지스터 ALT5
					 GPIO18, 19 – PWM0, PWM1
			 Software PWM :
				 CPU Clock에 의존하여 Pulse 생성
				 GPIO 제한 없슴
				 정확도 떨어짐
			 Library(Module) Support Level
				 Python Rpi.GPIO module
					 Software PWM only
				 NodeJs Onoff module
					 No PWM support
				 WiringPi (Python, NodeJs)
					 H/W, S/W support
		 LED Fade Circuit
		 python Rpi.GPIO module
			 S/W PWM support only
			 관련 함수
				 pwm = GPIO.PWM(pin, Hz)
				 pwm.start(duty_cycle)
				 pwm.ChangeDutyCycle(duty_cycle)
				 pwm.stop()
		 LED Fade
			 – python Rpi.GPIO module – pwm.py
		 WiringPi module
			 H/W PWM
				 GPIO pin limitation (12,13 / 18, 19)
				 wpi.pinMode(pin, wpi.PWM_OUTPUT)
				 wpi.pwmSetMode(mode)
					 { PWM_MODE_MS : Mark Space , wpi.PWM_MODE_BAL : Balanced(default) }
				 wpi.pwmSetClock(divisor)
					 19.2Mhz(PWM base clock) / divisor(분주비)
				 wpi.pwmSetRange(range)
					 Define Resolution, default = 1024
					 19.2M / divisor / range = Hz
				 wpi.pwmWrite(pin, value)
				 root privileges required(sudo)
		 LED Fade
			 python WiringPi module H/W PWM – pwm_wpi_hw.py
			 python WiringPi module H/W Clock PWM – pwm_wpi_hw_clk.py
		 WiringPi module
			 Soft Ware PWM
				 GPIO pin no limitation
					 each pin uses 0.5% of the CPU
				 wpi.pinMode(pin, wpi. OUTPUT)
				 wpi.softPwmCreate(pin, init_value, range)
					 Mininum Pulse Width 100μS, 100Hz for low CPU usage
					 Recommended range = 100
				 wpi.softPwmWrite(pin, value)
		 LED Fade
			 Python WiringPi module S/W PWM – pwm_wpi_sw.js
		 SG90 Servo Motor
			 180º 회전 가능
			 각도 별 제어 가능
			 Voltage : 4.8v ~ 6v
			 PWM Period : 50Hz(20ms)
			 PWM 펄스의 지속시간으로 회전각도 제어(1~2ms, datasheet)
				 0.5ms : -90º
				 1.5ms : 0º
				 2.5ms : +90º
		  Servo Motor 회로 구성
		 Servo Motor
			 Frequency : 50Hz
				 1초(1000ms)에 50Hz
				 1Period = 20ms(1000/50)
			 -90º : 0.5ms
				 1Period의 2.5%
					 0.5 / 20 = 0.025
			 0º : 1.5ms
				 1Period의 7.5%
					 1.5 / 20 = 0.075
			 +90º : 2.5ms
				 1Period의 12.5%
					 2.5 / 20 = 0.125
		 Servo Motor
			 Python WiringPi module S/W PWM Servo – servo_wpi_sw.py
			 Python WiringPi module H/W PWM Servo – servo_wpi_hw.py
		 Capacitor를 이용한 Analog Input
			 디지털 입력 핀으로 아날로그 흉내
			 RC회로(Resistor * Capacitor)
			 Capacitor (콘덴서)
				 교류는 통과, 직류는 차단
				 축전지
				 교류 전압 충전/방전
				 시 상수 (Time Constant)
					 전압의 63.2%를 충전하는데 걸리는 시간(초)
					 반복 : 나머지 전압의  63.2% 충전
					 TC = R x C
		 Capacitor를 이용한 Analog Input
			 저항의 크기에 따라 충전 시간 변화
			 캐패시터의 충전 시간 측정
				 가변저항 값 유추
			 고정저항 + 가변저항
				 1KΩ  + LDR
		 RC circuit LDR Analog Input
			 Python Rpi.GPIO module – rc_analog.py
		 RC circuit LDR Analog Input
			 Python WiringPi module – rc_analog_wpi.py
		 Ultra Sonic Sensor
			 Vcc : 5v
			 Trigger : GPIO 24 , 초음파 발생
			 Echo : GPIO 23, 반사되는 음파 인식
				 Raspberry-Pi GPIO 3.3v
				 Level Convertor
				 1K, 2K 저항
			 GND : Ground
		 Ultra Sonic Sensor
			 초음파를 발생시켜서 반사되는 시간으로 거리를 계산
			 Trigger pin에 10us 동안 HIGH
				 8번의 40hz 초음파 펄스 발생
			 Echo pin Low상태
				 펄스 발생 중
			 Echo pin HIGH 상태
				 펄스 발생 종료
			 Echo pin LOW 상태
				 반사 음을 수신
			 소요 시간
				 HIGH 상태인 동안의 시간
		 Ultra Sonic Sensor
			 소요시간으로 거리 계산
			 Speed of Sound
				 Depends on medium, temperature
				 343.21m/s in dry air 20 C (68  F)
				 34321cm/s
			 Speed = Distance / Time
			 34321 = distance / time
				 34321 = distance / (time/2)
					 왕복 시간
				 17160 = distance / time
				 17160 * time = distance
		 Ultra Sonic Sensor
			 Python Rpi.GPIO module – ultra_sonic.py
		 Ultra Sonic Sensor
			 Python WiringPi module – ultra_sonic_wpi.py
		 DHT-11 온도/습도 Module
			 온도/습도 센서를 Module로 구성
			 3핀
				 Red : Vcc (3~5V)
				 Green : Data Out
				 Black : GND
			 1Wire 통신
			 주어진 통신 체계에 마추어 신호 전달
				 MCU 요청신호가 전달되면 동작
				 HIGH 레벨 지속 시간에 따라 0, 1 구분
				 40bit 데이타(습도: 16bit, 온도: 16bit, CheckSum: 8bit
				 Real-time 요구
				 Rpi.GPIO, onoff Module 높은 실패율
				 wiringPi Module 또는 전용 Module 사용
				 https://akizukidenshi.com/download/ds/aosong/DHT11.pdf
		 DHT-11 온도/습도 Module
			 요청 신호(Start Signal) : HIGHjLOW(18ms) j PULL_UP
			 수신 데이타(40bit)  : 0 = 26~28us HIGH , 1= 50~70us HIGH
		  DHT-11 온도/습도 Module
			 40bit 전송 데이타
				 16bit 습도 (예: 53.0%)
					 8bit : 습도 상위 비트 (0011 0101) :53
					 8bit : 습도 하위 비트 (0000 0000) :  0
			 16bit 온도 (예: 24.0oC)
				 8bit : 온도 상위 비트 (0001 1000) : 24
				 8bit : 온도 하위 비트 (0000 0000) :   0
			 8bit : Check Sum (예: 0100 1001)
		 DHT-11 Sensor
			 Python Rpi.GPIO module – dht11.py<1/4>
		 DHT-11 Sensor
			 Python Rpi.GPIO module – dht11.py<2/4>
			 Python Rpi.GPIO module – dht11.py<3/4>
			 Python Rpi.GPIO module – dht11.py<4/4>
		  DHT-11 Sensor
			 Python Adafruit DHT module
				 https://learn.adafruit.com/dht/overview
			 Installation
				 cd ~
				 git clone https://github.com/adafruit/Adafruit_Python_DHT.git
				 cd Adafruit_Python_DHT
				 sudo python setup.py install
			 dht_adafruit.py
		 DHT-11 Sensor
			 Python WiringPi module – dht11_wpi.py <1/4>
			 Python WiringPi module – dht11_wpi.py <2/4>
			 Python WiringPi module – dht11_wpi.py <3/4>
			 Python WiringPi module – dht11_wpi.py <4/4>
		 Serial VS Parallel
			 Serial Communication
				 Send each bit consecutively
				 Slow
				 One Communication circuit
			 Parallel Communication
				 Send multiple bit at once
				 Fast
				 Need as much circuits as the number of sending bits
		  Serial Communication & Clock
			 Data is sent one by one consecutively
			 Need to distinguish one bit
			 Sender and receiver know same bit
		 Asynchronus  Serial Communication
			 Agreement on data distinguishing period
			 Do not send separate clock signal
			 If communication speed is different between
			 Two sides, it is impossible to communicate
			 Need extra starting and ending bit
			 Only 1:1 Communication
			 RS-232(UART) Communication Protocol
		 Synchronus Serial Communication
			 Data signal and bit distinguishing signal (Clock)
			 is separately sent
			 Recognize data signal on clock
			 No need to agree on speed
			 Limit on maximum speed
			 1:N Communication is possible
			 Master/Slave relations, Master leads clock
			 I2C, SPI Communication protocol
		 UART/RS-232
			 UART(Universal Asynchronus Receiver Transmitter)
				 Asynchronus Communication mechanical device
				 Most have internal MCU hardware
				 Able to decide clock start/end bit within software
				 Communication speed : Baud Rate
				 Use two data circuits
					 TxD(Transfer), RxD(Receive)
			 RS-232
				 US EIA(Eletronic Industries Association)
				 Standard for electronical and mechanical (Connector) traits for UART
				 Represents serial port in PC
			 UART/RS-232 Communication
				 MCU UART TTL(Transistor to Transistor Logic) : 0~5V
				 RS232 : -12V ~ +12V
				 RS232 – TTL transfer chip
					 MAX232 / Maxim
				 USB – TTL transfer chip
					 FT232R / FTDI Chip
					 CP2102 / Silicon Lab
		 RaspberryPi UART
			 UART Activation
				 sudo vi /boot/config.txt (Must back-up)
					 enable_uart=1
				 sudo vi /boot/cmdline.txt (Must back-up)
					 Delete below detail (getty disable)
					 console=serial0,115200
				 sudo reboot
				 ls /dev/serial*
					 Check below detail
						 serial0 --> ttyS0(UART)
						 serial1 --> ttyAMA0(Bluetooth)
					 Use device name connected to serial0
		 RaspberryPi URAT
			 Raspberry Pi – PC Communication
				 Transfer Device
					 RS232 to TTL Convertor
					 USB to Serial Convertor
					 Arduino
			 Communication b/w 2 Raspberry Pis
				 Cross connection of Tx, Rx jumper cable
				 Connect GND
			 Raspberry Pi – MCU Board(Arduino)  Communication
				 Connect GPIO UART Pin
				 Connect USB
		  UART Communication Between Two Raspberry Pis
			 Compose circuit (Tx –Rx Cross connection)
				 Tx – Rx
				 Rx – Tx
				 GND –GND
		 RaspberryPi - Arduino
			 Compose circuit (Tx –Rx Cross connection)
				 RaspberryPi Tx – Arduino Rx
				 RaspberryPi Rx(3.3v) – Arduino Tx(5v)
					 Level Convertor(Resistor)
					 R1 : 1KΩ
					 R2 : 2KΩ
				 GND -GND
		  minicom Setting
			 Setting
				 sudo apt-get install minicom
			 Execute
				 sudo minicom –b 115200 –D /dev/xxx
			 Setting
				 CTRL-A Z O
				 Q : local Echo on/off
				 P : Add line feed
				 T : Add Carriage Return
				 Esc
				 Save setup as dfl
		 RaspberryPi Serial Communication  Programming
			 Python serial Module
				 https://github.com/pyserial/pyserial
				 Install
					 pip3 install pyserial
					 or
					 sudo apt-get install python-serial
				 Basic API
					 import serial
					 port = serial.Serial(‘/dev/xxx’, baudrate=115200, timeout=1.0)
					 port.isOpen()
					 port.write(‘str’)
					 ch = port.read()
					 port.close()
		 RaspberryPi URAT Communication
			 Sender, Python Serial module – uart_write.py
			 Receiver, Python Serial module – uart_read.py
		 RaspberryPi URAT Communication
			 Two-way communication, Python Serial module – uart_rw.py
		 I2C(Inter Integated Circuit) Communication
			 Integrated Circuit Communication
			 Protocol for communication with MCU and peripheral devices
			 Developed by Philips
			 Communication Circuits: 2 circuits (TWI : Two Wire Interface)
				 SCL(Serial Clock)
				 SDA(Serial Data)
				 Need each circuits pull up resistor
			 Actual Communication circuit is only one (SDA)
				 Only half-double Communication is possible
				 Slow sending speed
			 Able to connect multiple devices to one bus
				 Have specific address (7bit) for Slave
				 Maxi 128(27) slave
				 No extra circuit for additional devices
		 Setting RaspberryPi
			 I2C Activation
				 sudo raspi-config
					 Advanced Options > A7 I2C
		 Setting RaspberryPi
			 Check device activation
				 ls –l /dev/i2c*
			 Check module loading in kernel
				 sudo vi /etc/modules
					 “i2c-dev”
					 Check detail, if no detail, add
				 lsmod
					 Check i2c_dev from the list
			 Allow I2C Communication
				 sudo vi /etc/modprobe.d/raspi-blacklist.conf
					 “blacklist i2c-bcm2708”
					 Delete detail or mark command
		 RaspberryPi – Arduion  I2C Communication
			 Circuit Connection
		 Arduino
			 Code Sketch
		 Setting RaspberryPi
			 I2C Tool installation
				 $ sudo apt-get install i2c-tools
			 I2C Bus Scan
				  $ i2cdetect –y 1
					 Check printing of slave address (0x04) designated in Arduino code
		 I2C Programming
			 Python smbus module
				 Installation
					 sudo apt-get install python-smbus
					 sudo apt-get install python3-smbus (python3의 경우)
					 https://github.com/bivab/smbus-cffi
				 Basic API
					 import smbus
					 bus = smbus.SMBus(busNo)
					 bus.write_byte(address, value)
					 bus.read_byte(address)
			 python smbus module - i2c.py
		 I2C Programming
			 NodeJs i2c module
				 Installation
					 npm install i2c
					 https://www.npmjs.com/package/i2cBasic API
				 Basic API
					 i2c = require('i2c')
					 wire = new i2c(addres, {device:'/dev/i2c-x'})
					 wire.writeByte(byte, function(err){})
					 wire.readByte(fnction(err, res){})
		 Rotary Potentiometer
			 Change resistor by switching handle
			 Pin1 : 5V, Pin2 : OUT, Pin3 : GND
			 Fade LED using Variable resistor value output
		  SPI(Serial Peripheral Interconnect) Communication
			 Serial Peripheral Interconnect Communication
			 Developed by Motorola
			 Communication   Circuits: 4
				 SCK, SCLK(Serial Clock): Master sends clock
				 MOSI(Master Output Slave Input): Master send
				 MISO(Master Input Slave Output): Master Receive
				 SS(Slave Select): Select slave by Master
					 Add one specific circuit for each slave
					 '0' to selected slave, '1' for remainder
			 Actual Communication circuits is two (MOSI, MISO)
			 All double Communication, Fast transfer
			 SPI Mode
				 Set start bit(0,1), clock bit(0,1)
		  MCP3008
			 ADC (Analog Digital Convertor)
			 10bit resolution (0~ 1023)
			 SPI Communication
			 Exercise variable resistor analog signal
		 Connect Circuit
			 Vdd – 3.3v
			 Vref – 3.3v
			 AGND – GND
			 CLK – CLK(GPIO11)
			 Dout – MISO(GPIO09)
			 Din – MOSI(GPIO10)
			 CS -  CE0(GPIO08)
			 CH0 – Variable resistor OUT
		 Reading Variable Resistor as MCP3008
		 SPI Activation
			 Raspberry-pi SPI Port Activation
				 sudo raspi-config
					 8.Advanced  Options > SPI > Yes
				 ls /dev/spi*
		 MCP3008 Communication
			 http://www.farnell.com/datasheets/808965.pdf
			 3Byte(24bit) Transfer/ Receive
			 SPI Mode : 0 (CPOL-0,CPHA-0)
			 Speed : 10kHz
			 Transfer
				 1: Start bit : 1
				 2: Channel configuration
				 3: Ignored
			 Receive
				 1: Ignored
				 2-3 : 10bit value
		 SPI Programming
			 Python Py-spidev
				 Installation
					 spidev Control Module (/dev/spidev0.0 ,  /dev/spidev0.1)
					 https://github.com/doceme/py-spidev
					 git clone git://github.com/doceme/py-spidev
					 cd py-spidev
					 Sudo python setup.py install
					 or
					 pip3 install spidev
				 Basic API
					 import spidev
					 spi = spidev.SpiDev()
					 spi.open(bus, channel)
					 recv_list = spi.xfer(send_list)
					 recv_list = spi.xfer2(send_list)
					 spi.max_speed_hz = hz
					 spi.mode = {0b01,0b11,0b10, 0b11}
		 Python spidev module
			 open(port, dev)
				 Port : 0
				 Dev :CE0 =0, CE1=1
			 xfer2([byte_1, byte_2, byte_3])
				 byte_1 : 1
				 byte_2 : channel config
					 1000 000 : channel 0
				 byte_3 : 0(ignored)
			 adc_out
				 r[0] : ignored
				 r[1] : Most significant 2 bit of 10bit
				 r[2] : Least significant 2 bit of 10bit
		 Bluetooth
			 Standard for personal short distance wireless comm.
				 1994 Ericsson (Swedish Communication Device Vendor)
				 SIG : Bluetooth Special Interest Group
				 https://www.bluetooth.com/
			 Classic Protocol
				 RFCOMM
					 Radio Frequency Communication
					 Replaced RS232 serial port to wireless
					 Similar to TCP
					 Able to use 30 port (Channel)
				 L2CAP
					 Logical Link Control and Adaption Protocol
					 Packet type, Max 672Bytes
					 Similar to UDP
					 Used as transfer layer of RFCOMM
				 ACL
					 Asynchronous Connection-oriented Logical
					 Similar to IP protocol, Use as sub protocol of L2CaP
				 SCO
					 Synchronous Connection-Oriented
					 Audio transfer protocol (64kb/s)
		 BlueZ
			 http://www.bluez.org
			 Library for Linux official Bluetooth Protocol Stack
			 bluez installation
				 sudo apt-get install bluez
			 bluez related command
				 hciconfig
					 Bluetooth device set
				 hcitool
					 Tool for command transfer and Bluetooth device connection
				 l2ping
					 Request  L2CAP echo/ping to given address
				 sdptool
					 Offer SDP (Service Discovery Protocol) for Bluetooth devices
				 frcomm
					 Set and manage Bluetooth sub system RFCOMM
					 Use Bluetooth as Serial(RS232)
				 bluetoothd
					 Service demon handling all Bluetooth devices
					 bluetoothd –v
		 Setting Communication Between Two Raspberry Pi
			 Server
				 sudo hciconfig
					 Check devices and address of installed Bluetooth
				 sudo hciconfig hci0 name “MyName”
					 Set hci0 name to show under scan list
				 sudo hciconfig hci0 piscan
					 Set hci0 to show under scan list, Enable Page and Inquiry scan
				 sudo hciconfig hci0 noscan
					 Set hci0 to not show under scan list, Disable Scan
			 Client
				 hcitool scan
					 Scan possible devices
				 sudo l2ping XX:XX:XX:XX:XX:XX
		 Setting Communication Between Two Raspberry Pi
			 Server
				 sudo vi /lib/systemd/system/bluetooth.service (Must back-up)
					 Add –C at the end of ‘bluetoothd’
					 Motion error due to version difference b/w bluez5 and SDP
					 sudo systemctl restart bluetooth
				 sudo sdptool browse local
					 Check serial port service in SDP
				 sudo sdptool add  SP
					 Add Serial Port service
				 sudo rfcomm listen /dev/rfcomm0
					 Connect to stand by /dev/rfcomm0
					 Need separate terminal connection under listening condition after connecting to client
				 sudo minicom –b 115200 –D /dev/rfcomm0
					 Serial communication with /dev/rfcomm0
			 Client
				 sudo rfcomm connect /dev/rfcomm0 XX:XX:XX:XX:XX
					 Connect and Bind to /dev/rfcomm0 with remote address channel
					 Eliminate: rfcomm release /dev/rfcomm0
				 sudo minicom –b 115200  –D /dev/rfcomm0
		 Android
			 Bluetooth Serial Controller
				 https://play.google.com/store/apps/details?id=nextprototypes.BTSerialController&hl=ko
				 Execute and connect after stand-by at Raspberry
		  Serial Communication
			 Server
				 sudo rfcomm listen /dev/rfcomm0   python bt_serial.py
			 Client
				 python bt_serial.py
		 Bluetooth Socket
			 Python Pybluez module
				 https://github.com/karulis/pybluez
				 sudo apt install libbluetooth-dev
					 dependency lib
				 sudo pip3 install pybluez
				 or
				 sudo apt-get install python-bluetooth
		 Bluetooth Device Scan
			 Python Pybluez module – bt_scan.py
		  Bluetooth Socket
			 Python  Server - bt_server.py
		 Bluetooth Socket
			 Python Client – bt_client.py
		  Service Discovery – bt_service_server.py
			 ServerSocket, Stand-by to connect to specific services (MyService)
				 sudo vi /lib/systemd/system/bluetooth.service (Must Back-up)
					 Add ‘-C’ at the end of ‘bluetoothd’
					 Error due to version difference b/w bluez5 & SDP
				 sudo service bluetooth restart  (/etc/init.d/bluetooth)
		 Service Discovery – bt_service_client.py
			 ClientSocket, Connect to specific services (MyService)
		 Service Discovery – bt_service_server.js
		 Service Discovery – bt_service_client.js
			 ClientSocket, Connect to specific services (MyService)
		 BLE
			 Bluetooth Low Energy
				 Bluetooth 4.0 Standard
				 Bluetooth SMART (BLE  Device, Sensor)
				 Bluetooth SMART Ready (Laptop, Smart Phone)
			 Profile
				 Conceptual standard difference for Bluetooth
				 motion & control
				 GAP,  Generic Access Profile
				 GATT, Generic Attribute Profile
				 ATT, Attribute Protocol
			 GAP
				 Control connection among devices
				 Distinguish motion
					 Advertising: Broadcast to other devices
					 Connection: Connecting two devices
			 Rolls
				 Central Device: PC, Smart Phone
				 Peripheral Device: Sensor etc.
		 BLE
			 GATT
				 Control communication among devices
				 Define data transfer methods using Service, Characteristic
				 Attribute
					 Minimum unit for data transfer /receive
				 Profile
					 Product
				 Service
					 Specific function
				 Characteristic
					 One value for one characteristic
			 Rolls:
				 GATT Server(Slave) :
					 Offer data
					 Sensor
				 GATT Client
					 Central Device
					 PC , Smart Phone
				 GATT Client (Request) j  GATT Server
		 Beacon
			 Advertising Specific Devices
			 iBeacon
				 Apple registered mark for indoor positioning system
				 Maxi 31byte payload within PDU
		 iBeacon Data Frame
			 Advertising Data
			 Max 31 Byte payload within PDU
				 Major/Minor Number
					 Recognize Beacon device
				 Tx Power
					 Signal strength measured within 1m of device
					 Use to calculate distance
		 Advertising / Connection
			 Advertising / Scanning
				 Advertising / Scan Response
				 Advertising Interval
				 Electric current consumption difference by Interval
			 Connection / Pairing
				 End Advertising
				 Scan impossible
				 Communication via GATT/Service/Characteristic
		 Making Raspberry-Pi with iBeacon
			 sudo hciconfig hci0 noscan
				 Scan halt
			 sudo hciconfig hci0 leadv3
				 None Connectable LE Advertising, leadv0 : Connectable
			 sudo hcitool -i hci0 cmd 0x08 0x0008 1E 02 01 1A 1A FF 4C 00 02 15 E2 0A 39 F4 73 F5 4B C4 A1 2F 17 D1 AD 07 A9 61 00 01 00 02 C8 00
				 Advertising send command
				 0x08 : OGF, Bluetooth command group
				 0x0008 : OCF, send Beacon command
				 1E 02 01 : AD Flag(3Byte), 총길이 30byte, General Discorverable Mode
				 1A 1A : AD Headers(2Bytes), Remainder length 26, Vendor AD Type
				 FF 4C 00 02: Vendor spec. data, Apple ID(4C 00), TypeId(02:iBeacon)
				 15 : Remainder length: 21
				 E2 0A 39 F4 73 F5 4B C4 A1 2F 17 D1 AD 07 A9 61 : UUID
				 00 01 : Major Number
				 00 02 : Minor Number
				 C8 : Tx Power
				 00 : Null EOF
			 sudo hciconfig hci0 noleadv
				 Advertising send halt
		 Check with Mobile App
			 Locate Beacon App , Radius Networks
			 Android
				 https://play.google.com/store/apps/details?id=com.radiusnetworks.locate&hl=ko
			 iPhone
				 https://itunes.apple.com/kr/app/locate-beacon/id738709014?mt=8
		 RaspberryPi Beacon Scanner
			 iBeacon Device
				 Locate App, Beacon Transmitter
					 Android 5.0+
				 Estimote
					 http://estimote.com/
				 SensorTag
					 http://www.ti.com/sensortag
				 HM-10
					 http://www.jnhuamao.cn/
					 Ti CC2540/2541 SoC base
		 RaspberryPi Beacon Scanner
			 hcidump Installation
				 sudo apt-get install bluez-hcidump
			 le scan
				 sudo hcitool lescan --duplicate
					 Exclude same device filtering
				 sudo hcidump --raw
					 Print detail lescan info
					 UUDI, Major/Minor, Tx analysis
		  RaspberryPi Beacon Scanner in Python
			 iBeacon Scanner
				 https://github.com/switchdoclabs/iBeacon-Scanner-
				 http://www.switchdoc.com/ Part of BeaconAir Project
			 Source download & execute
				 git clone https://github.com/switchdoclabs/iBeacon-Scanner-
				 cd iBeacon-Scanner-
				 sudo python testblescan.py
					 MAC addr, UUID, Major, Minor, Tx Power, RSSI
		 Python Beacon Scanner – beacon_scan.py
		  RaspberryPi Beacon Scanner in NodeJs
			 Noble
				 https://github.com/sandeepmistry/noble
				Refer to : https://blog.truthlabs.com/beacon-tracking-with-node-js-and-raspberry-pi-794afa880318#.khaba1d7m
		  Buzzer
			 Digital output
			 Material
				 Buzzer or Piezo
				 Variable Resistor (Volume Control)
				 Print frequency fit to compass
			 WiringPi softTone
				 oftToneCreate(PIN)
					 Print GPIO Pin #
				 softToneWrite(PIN, FREQUENCY)
					 Designate frequency value to print
		  Compose Circuit for Signal
		 Print Warning Sound
			 Python – buzzer.py
		  Twinkle Twinkle Little Star
			 Python – buzzer_littlestar.py
		  Audio Print
			 sudo raspi-config
				 Advanced Option -->  Audio
			 Audio Enable
				 /boot/config.txt
				 Dtparam=audio=on
			 Audio Print Modules
				 Python
					 pyaudio, pygame
				 NodeJs
					 play-sound
		  ALSA
			 Advanced Linux Sound Architecture
			 Linux Kernel Version 2.6 Basic Sound System
			 Replace OSS (Open Sound System)
			 Main utils
				 amixer
					 Sound system check and set
				 alsamixer
					 Sound volume control
				 alsactl
					 Sound driver advance setting
				 aplay
					 Recorder and Player
					 aplay ~/sample.wav
				 speaker-test
					 Print white noise
		 PyAudio
			 https://people.csail.mit.edu/hubert/pyaudio/
			 Installation
				 sudo apt-get install python-pyaudio
			 Function
				 Recoding
				 Wav Print, mp3 not supported
			 Main Function
				 p = pyaudio.PyAudio()stream = p.open()
				 stream.read(chunk)
				 stream.stop_stream()
				 stream.close()
				 p.terminate()
		 PyAudio
			 Wave File Play Block
		 PyAudio
			 Wave File Play Callback
		  Pygame mixer Module
			 http://www.pygame.org/docs/ref/music.html
			 Installation
				 sudo apt-get install python-pygame
				 Installed by default
			 Basic APIs
				 import pygame
				 pygame.init()
				 pygame.mixer.music.load(‘sample.mp3’)
				 pygame.mixer.music.play()
				 pygame.mixer.music.pause()
				 pygame.mixer.music.unpause()
				 pygame.mixer.music.stop()
		 Pygame mixer code
			 mp3.py
		 Raspi-Camera
			 https://www.raspberrypi.org/documentation/usage/camera/python/README.md
			 Connect to camera Interface
			 Activate Raspberry camera
				 sudo raspi-config
					 6. Enable Camera
		  Raspi-Camera
			 Take Photo
				 raspistill –o caputre1.jpg
					 Take still photo after 5 seconds
				 raspistill -0 capture2.jpg –w 1280 –h 720
					 Resolution 1280 x 720
			 Take Video
				 raspivid –o video.h264 –t 5000
					 Shoot video for five seconds
					 Check video
						 omxplayer path/video.h264
			 Notice
				 Preview not shown in VNC Viewer
				 Need to connect Display device
		 PiCamera Module
			 Picamera Module Installation
				 https://github.com/waveform80/picamera
				 sudo apt-get install python-picamera
			 Main Function
				 camera = picamera.PiCamera()
				 camera.rotation = 90
				 camera.resolution = (1280, 720)
				 camera.start_preview()
				 camera.capture(‘cam1.jpg’)
				 camera.start_recording(‘video.h264’)
				 camera.stop_recoding()
				 camera.stop_preview()
				 camera.close()
		 Pycamera Module
		 Camera Streaming
			 Remote Streaming of Video from Camera
			 Main Service
				 Motion: http://www.lavrsen.dk/foswiki/bin/view/Motion
				 MJPG-Streamer: https://sourceforge.net/projects/mjpg-streamer/
				 VLC: http://www.videolan.org/vlc/
		 Motion
			 Sense motion and record, Remote streaming
			 Install
				 sudo apt-get install motion
			 Sett
				 /etc/motion/motion.conf
					 stream_localhost on j off
			 Run & Shut down
				 sudo service motion stop
			 Motion Check
				 Connect to web browser
				 http://ip_address:8081
		 Camera Streaming
			 Insert motion view to web page
		 MJPG-Streamer
			 Install dependent package
				 sudo apt-get install libjpeg8-dev imagemagick libv4l-dev
			 Source code download
				 wget http://sourceforge.net/code-snapshots/svn/m/mj/mjpg-streamer/code/mjpg-streamer-code-182.zip
				 unzip mjpg-streamer-code-182.zip
				 cd mjpg-streamer-code-182/ mjpg-streamer
			 Apply patch
				 wget https://github.com/swkim01/RaspberryPiWithIOT/raw/master/ch7/input_uvc_patch
				 patch -p0 < input_uvc_patch
			 Build & Install
				 make USE_LIBV4L2=true clean all
				 sudo make DESTDIR=/usr install
			 Run
				 mjpg_streamer -i "input_uvc.so -d /dev/video0 -n -f 30 -r 1280x720" -o "output_http.so -n -w /usr/www"
		 MJPG-Streamer
			 Check result
				 Connect to web browser
				 http://ip_address:8080
		 VLC
			 Install
				 sudo apt-get install vlc
			 Start Streaming
				 raspivid -o - -t 0 -n | cvlc -vvv stream:///dev/stdin --sout '#rtp{sdp=rtsp://:8554/}' :demux=h264
			 Check VLC Video
				 Install VLC for PC
				 https://www.videolan.org/vlc/download-windows.ko.html
				 File > openNetwork > rtsp://IP_Address:8554/
		 OpenCV
			 http://opencv.org/
			 Open Source Computer Vision, Intel
			 Realtime Computer Vision Library
				 Official Support : C, C++, Python, Java
				 Non-officially support part of NodeJs (Do not support rendering)
			 Offer Various Function for Video Handling
				 Filter
				 Divider
				 Detect Characteristics
				 Detect Motion
				 Video Capture
			 Install
				 sudo apt-get install libopencv-dev
				 sudo apt-get install python-opencv (python 2 only)
			 v4l2 Loading
				 sudo apt-get install v4l-utils
				 sudo modprobe bcm2835-v4l2
				 ls /dev/video0
				 /etc/modules : auto load at booting time
		 Rendering Image File
			 cv_show.py
			 Printing GUI at Terminal
				 Select display device, DISPLAY=:0
				 Should connect VNC or monitor
				 e.g.: DISPLAY=:0 python cv_show.py
				 Or export DISPLAY=:0
		 Video Capture
			 cv_capture.py
		 Video File Play
			 cv_video_play.py
		 Camera Video Record
			 cv_camera_rec.py
		 Sense Motion
			 Difference Video
		 Sense Motion 
		 Image face/eye detecting
			 https://github.com/opencv/opencv/tree/master/data/haarcascades
		 Camera Face Sensor
		 General IoT Architecture
		 Web IoT  Communication Type
			 Remote Control
				 e.g. Turning On/Off Lamp, Heater, A/C, Audio,  Moving Camera etc.
				 Send Command and Get Result
				 HTTP Request and Response
			 Periodic Monitoring
				 e.g. CPU, Memory, Temperature, Humidity etc.
				 Long term interval
				 Typical Polling
				 HTTP Request and Response + Ajax
			 Real-Time Notification(Server Push)
				 e.g. Alarm of Fire/Intrusion/Emergency bell etc.
				 Server Push
				 WebSocket/MQTT/XMPP
		 Web Remote Control
			 LED On/Off
				 LED GPIO #18
		 Web Remote Control
			 /static/led.html <1/3>
			 /static/led.html <2/3>
			 /static/led.html <3/3>
			  Python – led.py <1/2>
		 Web Remote Control
			 Python – led.py<2/2>
		 Web Remote Monitoring
			 Monitoring Temperatur/Humidity
				 DHT-11 GPIO #24
		 Web Remote Monitoring
			 dht11.html <1/3>
			 dht11.html <2/3>
			 dht11.html  <3/3>
		 Web Remote Monitoring
			 Python - dht11.py  <1/2>
		 Web Remote Monitoring
			 Python - dht11.py  <2/2>
		 Web Remote Notification
			 Button Switch Bush
				 Button Switch GPIO #23
		 Web Remote Notification
			 btn_notify.html <1/2>
			 btn_notify.html <3/3>
		 Web IoT Combined
			 Client
				 HTML - /static/web_iot.html
			 Server
				 Python – web_iot.py
				 NodeJs – web_iot.js
		 Web IoT Combined
			 HTML - web_iot.html <1/3>
		 Web IoT Combined
			 HTML - web_iot.html <2/3>
		 Web IoT Combined
			 HTML - web_iot.html <3/3>
		 Web IoT Combined
			 Python - web_iot.py <1/2>
		 Web IoT Combined
			 Python - web_iot.py <2/2>
		 Camera Streaming
			 OpenCV + Web Programming
				 Base64 Encoding
				 data:image/png;base64,
			 Client
				 /static/cam.html
			 Server
				 Python
					 cam.py
				 NodeJs
					 cam.js
		 Camera Streaming
			 HTML – /static/cam.html <2/3>
		 Camera Streaming
			 HTML – /static/cam.html <3/3>
		  Camera Streaming
			 Python – cam.py <1/2>
		 Camera Streaming
			 Python – cam.py <2/2>
		 Arduino?
			 Origin of the Name
				 Arduin: King of Ivrea, Italy (1002), Ousted by Henry II of Germany
				 Bar di Re Arudino: Favorite pub of Arduino developer
			 Massimo Banzi
				 Professor at IDII(Interaction Design Institute Ivera)
					 In Ivrea, Italy
					 College specialized in Art and IT convergence
				 Derived from Wiring, Master’s thesis of a IDII, Colombia University
				 Co-developed Arduino with his colleague David Cuartielles
				 Inspired by program language Processing, made by MIT for designers
		  Arduino
			 Open Source H/W Prototyping Platform
			 Arduino Board + IDE + Community
		 Arduino Borads
			 http://arduino.cc/en/Main/Products
		 Arduino
		 Arduino
		  Arduino Interactive
		 Arduino IDE
			 http://arduino.cc/en/Main/Software
			 Windows, Mac, Linux
		 Driver Installation
			 For Windows
			 Connect PC and Arduino
			 Start -> Control Panel ->
			System -> Device Manager
			 Update Driver from COMXX list
			 Select Arduino installation directory /Drivers
		 Arduino IDE - Windows
			 Install Driver & Open Device Manager
			 Check COM & LPT List
				 COM Port number differs by device
			 ArduIDE Execution
				 Arduino.exe
				 Tool > Serial Port
				 Select COM port checked at device
		 Arduino IDE - Mac
			 No need to install Driver
			 ArduIDE Execution
				 Arduino.app
				 Tool > Serial Port
				 Select /dev/tty.usbmodemXXX
		  Arduino IDE
		 Arduino HelloWorld
			 Compose Circuit
				 LED
					 Short leg to GND
					 Long leg to 13
			 Sketch
				 File> Example > 01.Basics > Blink
				 Compile, Upload
			 Experiment Result
				 LED Blink next to 13 port
		 Architecture of Sketch (Source Code)
			 C/C++ Language
			 Use its own Pre-processor
				 Not standard C/C++
				 Able to call before function decl.
				 Binary Notation (0b or 0B)
			 Setup()
				 Initial one call, initialization
			 loop()
				 Function running while power on
				 Infinite repetition
			 Build Process
				 Create middle file with main function
					 #include "arduino.h"
					 hardware/arduino/cores/arduino/
				 avr-gcc Compile
					 hardware/tools/avr/bin/
				 *.o File link & Upload
		 Data Types
		 In/Output Basic Function
			 pinMode(pin, mode)
				 Set designated pin to in/output
				 pin: # of pin to set
				 mode : INPUT, OUTPUT, INPUT_PULLUP
			 delay(ms)
				 Halt program for certain amount of time
				 ms: Time to halt, milliseconds, unsigned long
			 digitalWrite(pin, value)
				 Print HIGH (5V) or Low (0V) to designated pin
				 pin: # of Pin to output
				 value: HIGH or LOW
			 digitalRead(pin)
				 Input HIGH or LOW to given pin value (to read in)
				 pin: # of Pin to input
		 LED Blink
			 Arduino’s HelloWorld
			 LED Blink
			 Part
				 LED(Light Emitting Diode)
					 Short Leg : Cathode, Negative( - )
					 Long Leg: Anode, Positive( + )
					 Cathode head is cut.
				 Register
					 Interfere electric flow
					 Decrease Voltage or electric current
					 No Electrode
					 Unit: Ω(ohm)
			 Connect Circuit
				 LED Long Leg: 13 Port + Resistor
				 LED Short Leg: GND
		 LED Blink Sketch
		  Serial Monitor
			 Serial Communication tool t/w Arduino and PC
			 Tools > Serial Monitor or Short Cut command Ctrl + Shift + M
			 Select Baud(Transfer Speed) same as Sketch
		 Serial Input Output
			 Serial.begin(baud)
				 Same value for Baud transfer speed and transfer/receive
				 Serial.begin(9600)
			 Serial.available()
				 Readable bites (Saved in Buffer)
				 Serial.read()  Check with if sentence before call
			 Serial.read()
				 Turn around by reading first bit
				 When there is no data, turnaround -1
			 Serial.write()
				 Output binary data
			 Serial.print();
				 Output ASCII Text
			 Serial.println()
				 Add line feed character to print() function
			 SerialEvent
				 Call when serial data is arrived
		  Print Serial Monitor
			 Hello World
		 LED On/Off with Serial Monitor
			 Execute at Loop
		 LED On/Off with Serial Monitor
			 Execute at SerialEvent
		 Input Push Button Switch
			 On/Off LED with button switch
			 Button Switch
				 Two legs are connected
				 Connecting two legs of four is enough
			 Connect Circuit
				 13 pin – LED – GND
				 Pulldown resistor
					 5V – button – 10k resister – GND
					 Button -  Digital 7 pin
				 Pullup resistor
					 5V – 10k Resistor – Button – Digital 7 pin
					 Button – GND
		 Push Button Switch Circuit (Pull Up Resistor)
		 Push Button Switch Circuit (Pull Down Resistor)
		 Push Button Switch Sketch
		 Push Button Circuit (Internal Pullup)
			 Offer pull up resistor MCU internally
			 pinMode(PIN, INPUT_PULLUP);
			 0,1 cannot be used simultaneously with serial comm.
		  Relay Switch Sketch
			 Same as LED Blink
		 Composing LED Fade Circuit
		 LED Fade Sketch
		 Analog Input
			 ADC(Analog to Digital Converter) included
				 Analog-Digital Transducer
				 A0 ~ A5 (6 pins)
				 Declare in order of constant A0 = 14, A1=15
				 10 bit resolution: 0~1023
				 analogRead()
			 Rotary Potentiometer
				 Necessary parts
					 Rotary Variable Resistor
						 Change resistor value by turning handle
						 Pin1 : 5V, Pin2 : OUT, Pin3 : GND
					 220Ω Resistor
					 LED
		 Composing Variable Resistor Circuit
		 Composing Variable Resistor Circuit
		 External Library
			 Library not included in Arduino IDE
			 Must be installed separated as needed
			 Able to re-use well-used function by drafting them as library
			 Have a same name folder within the library folder
		 Adding Library
			 Sketchbook location
				 Windows : File > Setting
				 Mac : Arduino > Setting
			 Copy external library directory file to library directory
				 Special characters are not allowed in directory name
			 Restart Arduino IDE
			 Sketch  > Get Library  > Select
		  DHT-11 Temperature/ Humidity Module
			 Compose temp./humidity sensor as module
			 4 pins
				 1 : Vcc (3~5V)
				 2 : Data Out
					 Need 10k pull up resistor
					 Cannot use Internal pull up (100k)
				 3 : Not used
				 4 : GND
			 Have DHT-22 as well with better function
			 https://learn.adafruit.com/dht/overview
		  Composing DHT-11 Circuit
		 DHT-11 Library
			 https://github.com/adafruit/DHT-sensor-library
			 Change the folder name to “DHT” after unzipping
			 Copy to /libraries/
			 Restart IDE
		 DHT-11 Sketch  (Cont.)