arduino/02_digital/digital_input_pullup/main.py

Reads a pushbutton on D2 using the pin's pull-up resistor, so no other parts are needed, prints its state and lights the on-board LED while it is pressed.

Wiring

A pushbutton between D2 and GND. The pull-up holds D2 at 1 while the button is open, so the logic is inverted: pressed reads 0.

# Reads a pushbutton on D2 using the pin's pull-up resistor, so no other parts
# are needed, prints its state and lights the on-board LED while it is pressed.
#
# Connect a pushbutton between D2 and GND. The pull-up holds D2 at 1 while the
# button is open, so the logic is inverted: pressed reads 0.
 
from arduino import *  # the Arduino-style functions: pinMode(), digitalWrite(), delay(), ...
 
BUTTON_PIN = 2  # the pushbutton is on D2
 
 
def setup():
    pinMode(BUTTON_PIN, INPUT_PULLUP)  # D2 as an input, held HIGH until pressed
    pinMode(LED_BUILTIN, OUTPUT)  # the LED's pin as an output
 
 
def loop():
    state = digitalRead(BUTTON_PIN)  # LOW while pressed (the button connects D2 to GND), HIGH when not
    print(state)
    if state == LOW:  # pressed
        digitalWrite(LED_BUILTIN, HIGH)  # LED on
    else:
        digitalWrite(LED_BUILTIN, LOW)  # LED off
    delay(100)  # ten readings a second
 
 
# Do not edit below this line: it runs setup() once, then loop() over and over.
def main():
    setup()  # runs once, at the start
    while True:  # repeats until stopped: Interrupt in PyCharm, or mpremote soft-reset
        loop()
 
 
# True when this file is run, but not when another file imports it.
if __name__ == "__main__":
    main()