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USB HID Keyboard

Overview

The USB HID Keyboard sample demonstrates using the USB Human Interface Device (HID) module to implement a keyboard input device that you can connect to your computer.

This sample code enumerates the nRF52840 Connect Kit into a HID keyboard that has an A key connected to the USER button.

Tip

adafruit_hid is pre-built into CircuitPython as a frozen module, so that it can be imported in the code directly.

Requirements

Before you start, check that you have the required hardware and software:

Running the code

To run the code, complete the following steps:

  1. Connect nRF52840 Connect Kit to your computer using the USB-C Cable.
  2. Start Mu Editor, click Load to open code.py in the CIRCUITPY drive.

  3. Copy and paste the following code into code.py and click Save:

    CIRCUITPY/code.py
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    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

# USER button acts as A key on a keyboard
key_a = digitalio.DigitalInOut(board.USER)
key_a.direction = digitalio.Direction.INPUT
key_a.pull = digitalio.Pull.UP

# LED0 indicates A key is pressed
led = digitalio.DigitalInOut(board.LED0)
led.direction = digitalio.Direction.OUTPUT

# 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)

print("Waiting for key pin...")

while True:
    if not key_a.value:
        print("Key A pressed!")

        # Turn on LED0
        led.value = False

        while not key_a.value:
            pass    # Wait for key A released

        # Type keycode `Shift+A`
        keyboard.press(Keycode.SHIFT, Keycode.A)
        keyboard.release_all()

        # Turn off LED0
        led.value = True

    time.sleep(0.01)

  4. Your code will run as soon as the file is done saving. The board will enumerate as a HID keyboard. Click Serial on Mu Editor's Top Menu to open a serial console. You should see the console output, similar to what is shown in the following:

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    Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.
code.py output:
Waiting for key pin...

  5. Open a text editor and press USER button on the board. Every button press sends a character A to the computer, and this will be displayed in the text editor.