arduino/01_basics/fade/main.py

Fades the on-board LED up and down with PWM, about once every three seconds. analogWrite() takes 0 (off) to 255 (fully on); the brightness goes up in 51 steps of 5, 30 ms apart, then back down.

Uses

analogWrite(), delay()

# Fades the on-board LED up and down with PWM, about once every three seconds.
#
# analogWrite() takes 0 (off) to 255 (fully on); the brightness goes up in 51
# steps of 5, 30 ms apart, then back down.
 
from arduino import *  # the Arduino-style functions: pinMode(), digitalWrite(), delay(), ...
 
STEP = 5  # how much the brightness changes each time: 255 / 51
 
brightness = 0  # current brightness: 0 = off, 255 = fully on
fade_amount = STEP  # added to brightness each pass: positive brightens, negative dims
 
 
def setup():
    pass  # analogWrite() sets the pin up the first time it is called
 
 
def loop():
    global brightness, fade_amount  # loop() changes both, so it needs the ones above
    analogWrite(LED_BUILTIN, brightness)  # the fraction of the time the LED is on, out of 255
    brightness += fade_amount  # one step brighter (or dimmer) for next time
    if brightness <= 0 or brightness >= 255:
        fade_amount = -fade_amount  # at either end, turn round and go the other way
    delay(30)  # 30 ms per step, so the fade is smooth
 
 
# 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()