One of the things we baked into CircuitPython is 'HID' control - Keyboard and Mouse capabilities. This means a Circuit Playground Express can act like a keyboard device and press keys, or a mouse and have it move the mouse around and press buttons. This is really handy because even if you cannot adapt your software to work with hardware, there's almost always a keyboard interface - so if you want to have a capacitive touch interface for a game, say, then keyboard emulation can often get you going really fast!
Then try running this example code which will set the Circuit Playground Express Button_A and Button_B as HID keyboard "keys".
# SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries
#
# SPDX-License-Identifier: MIT
# Circuit Playground HID Keyboard
import time
import board
import usb_hid
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS
from adafruit_hid.keycode import Keycode
from digitalio import DigitalInOut, Direction, Pull
# A simple neat keyboard demo in CircuitPython
# The button pins we'll use, each will have an internal pulldown
buttonpins = [board.BUTTON_A, board.BUTTON_B]
# our array of button objects
buttons = []
# The keycode sent for each button, will be paired with a control key
buttonkeys = [Keycode.A, "Hello World!\n"]
controlkey = Keycode.SHIFT
# the keyboard object!
# sleep for a bit to avoid a race condition on some systems
time.sleep(1)
kbd = Keyboard(usb_hid.devices)
# we're americans :)
layout = KeyboardLayoutUS(kbd)
# make all pin objects, make them inputs with pulldowns
for pin in buttonpins:
button = DigitalInOut(pin)
button.direction = Direction.INPUT
button.pull = Pull.DOWN
buttons.append(button)
led = DigitalInOut(board.D13)
led.direction = Direction.OUTPUT
print("Waiting for button presses")
while True:
# check each button
# when pressed, the LED will light up,
# when released, the keycode or string will be sent
# this prevents rapid-fire repeats!
for button in buttons:
if button.value: # pressed?
i = buttons.index(button)
print("Button #%d Pressed" % i)
# turn on the LED
led.value = True
while button.value:
pass # wait for it to be released!
# type the keycode or string
k = buttonkeys[i] # get the corresponding keycode or string
if isinstance(k, str):
layout.write(k)
else:
kbd.press(controlkey, k) # press...
kbd.release_all() # release!
# turn off the LED
led.value = False
time.sleep(0.01)
Press Button A or Button B to have the keypresses sent.
The Keyboard and Layout object are created, we only have US right now (if you make other layouts please submit a GitHub pull request!)
# the keyboard object!kbd = Keyboard(usb_hid.devices)# we're americans :)layout = KeyboardLayoutUS(kbd)
Then you can send key-down's with kbd.press(keycode, ...) You can have up to 6 keycode presses at once. Note that these are keycodes so if you want to send a capital A, you need both SHIFT and A. Don't forget to call kbd.release_all() soon after or you'll have a stuck key which is really annoying!
You can also send full strings, with layout.write("Hello World!\n") - it will use the layout to determine the keycodes to press.
