Python For Microcontroller, Raspberry Pi

Keyboard Emulator Using Raspberry Pi Pico (Maker Pi Pico) and CircuitPython

by Idris
February 16, 2021

CircuitPython, Raspberry Pi Pico, USB Keyboard

Program USB HID on Raspberry Pi Pico.

Introduction

For your information, USB on Raspberry Pi Pico also supports HID (Human Interface Device). It means you can turn this Maker Pi Pico into a USB keyboard, mouse or joystick. In this tutorial, we will try to emulate as a USB keyboard first. So, how to make it? Let’s try.

Video

This video shows how to turn the Maker Pi Pico into a USB keyboard using CircuitPython.

Hardware Preparation

List of items used in the video.

Maker Pi Pico

USB Micro B Cable

Sample Program

This is the CircuitPython code for Maker Pi Pico (Raspberry Pi Pico) to emulate as a USB keyboard.

#

# Keyboard Emulator Using Maker Pi Pico and CircuitPython

#

# References and credit to

# – https://learn.adafruit.com/circuitpython-essentials/circuitpython-hid-keyboard-and-mouse

#

# Raspberry Pi Pico

# – [Maker Pi Pico] https://my.cytron.io/p-maker-pi-pico?tracking=idris

#

# Additional Libraries

# – adafruit_hid

#

# Update:

# 12 Feb 2021 – Tested with CircuitPython Pico 6.2.0-beta.2

#

import time

import board

import digitalio

import usb_hid

from adafruit_hid.keyboard import Keyboard

from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS

from adafruit_hid.keycode import Keycode

# A simple neat keyboard demo in CircuitPython

# The pins we'll use, each will have an internal pullup

keypress_pins = [board.GP20, board.GP21, board.GP22]

# Our array of key objects

key_pin_array = []

# The Keycode sent for each button, will be paired with a control key

keys_pressed = [Keycode.A, "Hello, World!", "https://cytron.io/p-maker-pi-pico\n"]

control_key = Keycode.SHIFT

# The keyboard object!

time.sleep(1)  # Sleep for a bit to avoid a race condition on some systems

keyboard = Keyboard(usb_hid.devices)

keyboard_layout = KeyboardLayoutUS(keyboard)  # We're in the US 🙂

# Make all pin objects inputs with pullups

for pin in keypress_pins:

    key_pin = digitalio.DigitalInOut(pin)

    key_pin.direction = digitalio.Direction.INPUT

    key_pin.pull = digitalio.Pull.UP

    key_pin_array.append(key_pin)

# For most CircuitPython boards:

led = digitalio.DigitalInOut(board.GP28)

# For QT Py M0:

# led = digitalio.DigitalInOut(board.SCK)

led.direction = digitalio.Direction.OUTPUT

print("Waiting for key pin…")

while True:

    # Check each pin

    for key_pin in key_pin_array:

        if not key_pin.value:  # Is it grounded?

            i = key_pin_array.index(key_pin)

            print("Pin #{} is grounded.".format(i))

            # Turn on the red LED

            led.value = True

            while not key_pin.value:

                pass  # Wait for it to be ungrounded!

            # "Type" the Keycode or string

            key = keys_pressed[i]  # Get the corresponding Keycode or string

            if isinstance(key, str):  # If it's a string…

                keyboard_layout.write(key)  # …Print the string

            else:  # If it's not a string…

                keyboard.press(control_key, key)  # "Press"…

                keyboard.release_all()  # …"Release"!

            # Turn off the red LED

            led.value = False

    time.sleep(0.01)