I finally got around to tinkering with the Raspberry Pi hardware. A while ago I’d ordered a basic electronic kit from ebay with a breadboard and a bunch of electronic components (resistors, cables, etc) in it. I started with a rather elementary project: control of an LED and a push-button from the Pi. Despite its apparent simplicity it’s a good opportunity re-learn some basics: which is the anode/cathode of the LED? What’s a pull-up/pull-down resistor? and so on…
Here’s the final ‘product’:
I needed to cut open up my fancy cardboard case :-( to gain access to the GPIO ports on the Pi. I may design a new case in the future, one that allows direct connection to the board.
The drive this wonderful piece of hardware, I wrote the following code that makes the LED blinking (yaaaay):
# led_blink.py import time import RPi.GPIO as GPIO # Set the mode of numbering the pins. GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) # Initialise GPIO10 to high (true) so that the LED is off. status = True while 1: GPIO.output(12, status) status = not status time.sleep(1)
and this program turns the LED on when the button is pressed:
# led_button.py import RPi.GPIO as GPIO # Set the mode of numbering the pins. GPIO.setmode(GPIO.BOARD) GPIO.setup(11, GPIO.IN) GPIO.setup(12, GPIO.OUT) # Initialise to high (true) so that the LED is off. GPIO.output(12, True) button_pressed = False while 1: if GPIO.input(11): if not button_pressed: print 'Button pressed.' button_pressed = True GPIO.output(12, False) else: if button_pressed: print 'Button released.' button_pressed = False # When the button switch is not pressed, turn off the LED. GPIO.output(12, True)
I took the inspiration and some sample code from the following places: