USB keypress code for AdaFruit Trinket M0 with CircuitPython 4

main.py

import digitalio
from board import *
import time
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode
import adafruit_dotstar

# The keycode sent for each button, optionally can be paired with a modifier key
# https://circuitpython.readthedocs.io/projects/hid/en/latest/api.html#adafruit-hid-keycode-keycode
button_keycode = 83
modifier_keycode = None # e.g. Keycode.RIGHT_ALT

led = adafruit_dotstar.DotStar(APA102_SCK, APA102_MOSI, 1)
led[0] = (0, 255, 0)
led.brightness = 0.0

kbd = Keyboard(usb_hid.devices)

button = digitalio.DigitalInOut(D0)
button.direction = digitalio.Direction.INPUT
button.pull = digitalio.Pull.UP

print("Waiting for button press: keycode %s with modifiers %s" % (button_keycode, modifier_keycode))

while True:
    if (not button.value):   # pressed?
        print("Button pressed")

        if modifier_keycode is not None:
            kbd.press(button_keycode, modifier_keycode)
        else:
            kbd.press(button_keycode)
        led.brightness = 1.0

        while (not button.value):
            pass
        
        print("Button released")

        kbd.release_all()
        led.brightness = 0.0

    time.sleep(0.01)

Simplified code for USB footpedal or similar. Also ensures LED is only active when pressed.