40pin IO Development

Experiment 03 - Button Control LED On/Off

Hardware Connection

Connect the button circuit to IO37 (you can use a DuPont wire instead of a button), and connect the LED bulb to IO31.

Software Operation

Enter the user home directory and run:

cd user
sudo python3 ./button_led.py

Terminal as shown:

You can see that when the button is pressed IO31 outputs low level; when released IO31 outputs high level (LED on/off).

#!/usr/bin/env python3
import sys
import signal
import Hobot.GPIO as GPIO
import time


def signal_handler(signal, frame):
    sys.exit(0)


# Define GPIO channels:
# led_pin as output to light an LED
# but_pin as input to connect a button
led_pin = 31 # BOARD pin 31
but_pin = 37 # BOARD pin 37

# Disable warnings
GPIO.setwarnings(False)


def main():
    prev_value = None
    # Pin Setup:
    GPIO.setmode(GPIO.BOARD)  # BOARD pin-numbering scheme
    GPIO.setup(led_pin, GPIO.OUT)  # LED pin set as output
    GPIO.setup(but_pin, GPIO.IN)  # Button pin set as input

    # Initial state for LEDs:
    GPIO.output(led_pin, GPIO.LOW)
    print("Starting demo now! Press CTRL+C to exit")
    try:
        while True:
            curr_value = GPIO.input(but_pin)
            if curr_value != prev_value:
                GPIO.output(led_pin, curr_value)
                prev_value = curr_value
                print("Outputting {} to Pin {}".format(curr_value, led_pin))
            time.sleep(1)
    finally:
        GPIO.cleanup()  # cleanup all GPIO


if __name__ == '__main__':
    signal.signal(signal.SIGINT, signal_handler)
    main()