our keyboard example combining Processing and the CPX; the CPX side

P5xCPX__CPXside.py

# our imports
# ------------------------------------------------------> 
import usb_hid
"""
note that, this HID functionality is unique to the 
circuit python express (there is an older "non-express"
version that is discontinued). Because of this we import 
cpx, rather than cp.
"""
from adafruit_circuitplayground.express import cpx

"""
use this to act as the keyboard 
this is where the "send" commands from the 
CPX to the computer come from
"""
from adafruit_hid.keyboard import Keyboard

"""
these are all the codes we use to give 
the specific "code" of the key we want to 
pretend to press. If we didn't have this
we'd have to refer to a table of numbers
or something like this.
"""
from adafruit_hid.keycode import Keycode
# ------------------------------------------------------> 

# our keyboard object
# this does some setting up
kbd = Keyboard(usb_hid.devices) 

# ------------------------------------------------------> 
while True:
    # if we press button a, send an O or an o 
    # the switch controls the shift key
    # ----------------------------------->
    if cpx.button_a:
        if cpx.switch: 
            kbd.send(Keycode.SHIFT, Keycode.A) 
        else:
            kbd.send(Keycode.A)
        while cpx.button_a: 
            # pass means do nothing
            # we just need to do this
            # to prevent multiple undesired
            # keypresses.
            pass
        
    # if we press button b, 
    # send an X or an x, depending
    # on whether the switch is "on"
    # ----------------------------------->
    if cpx.button_b:
        if cpx.switch:
            kbd.send(Keycode.SHIFT, Keycode.B)
        else: 
            kbd.send(Keycode.B)
        while cpx.button_b: 
            pass
# ------------------------------------------------------>