arduino/02_digital/blink_without_delay/main.py

Blinks the on-board LED once a second without delay(), so loop() is free to do other work between changes. Each pass checks how long it has been since the last change with millis(), which never wraps round, so plain subtraction works.

# Blinks the on-board LED once a second without delay(), so loop() is free to
# do other work between changes. Each pass checks how long it has been since
# the last change with millis().
 
from arduino import *  # the Arduino-style functions: pinMode(), digitalWrite(), delay(), ...
 
INTERVAL_MS = 500  # time between changes, in milliseconds
 
led_state = LOW  # the LED's level: LOW = off, HIGH = on
previous_ms = 0  # the time of the last change
 
 
def setup():
    pinMode(LED_BUILTIN, OUTPUT)  # the LED's pin as an output
 
 
def loop():
    global led_state, previous_ms  # loop() changes both, so it needs the ones above
    now = millis()  # milliseconds since the board started
    if now - previous_ms >= INTERVAL_MS:  # millis() never wraps round, so plain subtraction works
        previous_ms = now  # remember when this change happened
        led_state = HIGH if led_state == LOW else LOW  # swap on and off
        digitalWrite(LED_BUILTIN, led_state)
    # Nothing here waits, so other work can go here and still run every pass.
 
 
# 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()