Lecture 31 Toggling an LED

1. Toggle LED by running the program on the board:

1. Connect the USB cable of the keyboard and the mouse to the Board. Connect the board and the monitor with an HDMI cable.
2. Make sure the SD card is in the socket on the board.
3. Power up the board and just wait for a bit. You should see the Linux operating system desktop similar to this: (may have a different backgroud):



Click the Raspberry icon on the top-left corner of the view, select Programming - Python 3 (IDLE) to open the console.


To open an independent script file, select File - New File. In the new window, select File - Save As. Ust test.py as the file name and save it on the desktop of the linux system.



Open a linux terminal, install rpi.gpio package: (make sure you have the wifi connection first)


According to the Pin Map of the PI board, connect BCM 23 to the resistor, and connect any of the GROUND pin to the cathode of the LED.
The Pin Map can be found below:





Type the following code into your new script window and save it.


This will turn on Pin 23 permanently. A dead loop is bad, the PI will run this forever, which is power-consuming.
You can make the LED flash for a certain period of time and turn it off:
Modify the code:



Then, run this code at the Linux terminal:

>> sudo python test.py

The LED will be turned on for 1 second and then off. You can modify the number in the 'sleep()' function to change the delay time. It can be even 0.1s, or 0.01s, etc.
 
2. Toggle LED by GUI
Type the following code into a new script file, test_1.py, click Run in the menu.



A short demo video can be found below:




Tasks:

Demonstrate the following:

1. Repeat my work to toggle the LED by downloading the code to the board. (50 points)
2. Toggle the LED using a GUI button in Linux.
(50 points)