Once your Feather nRF52840 is set up with CircuitPython you'll also need to add some libraries. Follow this page for info on how to download and add libraries to your Feather.

From the library bundle you downloaded in that guide page, transfer the following libraries onto the Feather's /lib directory:

  • adafruit_ble
  • adafruit_bus_device
  • adafruit_hid
  • neopixel.mpy
  • simpleio.mpy

Text Editor

Adafruit recommends using the Mu editor for using your CircuitPython code with the Feather boards. You can get more info in this guide.

Alternatively, you can use any text editor that saves files.

Code.py

Copy the code below and paste it into Mu. Then, save it to your Feather as code.py.

For a full list of HID keycodes, check out these docs.

"""
This example acts as a BLE HID keyboard to peer devices.
Attach five buttons with pullup resistors to Feather nRF52840
  each button will send a configurable keycode to mobile device or computer
"""
import time
import board
from digitalio import DigitalInOut, Direction

import adafruit_ble
from adafruit_ble.advertising import Advertisement
from adafruit_ble.advertising.standard import ProvideServicesAdvertisement
from adafruit_ble.services.standard.hid import HIDService
from adafruit_ble.services.standard.device_info import DeviceInfoService
from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keyboard_layout_us import KeyboardLayoutUS
from adafruit_hid.keycode import Keycode

button_1 = DigitalInOut(board.D11)
button_2 = DigitalInOut(board.D10)
button_3 = DigitalInOut(board.D9)
button_4 = DigitalInOut(board.D6)
button_5 = DigitalInOut(board.D5)

button_1.direction = Direction.INPUT
button_2.direction = Direction.INPUT
button_3.direction = Direction.INPUT
button_4.direction = Direction.INPUT
button_5.direction = Direction.INPUT

hid = HIDService()

device_info = DeviceInfoService(software_revision=adafruit_ble.__version__,
                                manufacturer="Adafruit Industries")
advertisement = ProvideServicesAdvertisement(hid)
advertisement.appearance = 961
scan_response = Advertisement()
scan_response.complete_name = "CircuitPython HID"

ble = adafruit_ble.BLERadio()
if not ble.connected:
    print("advertising")
    ble.start_advertising(advertisement, scan_response)
else:
    print("already connected")
    print(ble.connections)

k = Keyboard(hid.devices)
kl = KeyboardLayoutUS(k)
while True:
    while not ble.connected:
        pass
    print("Start typing:")

    while ble.connected:
        if not button_1.value:  # pull up logic means button low when pressed
            #print("back")  # for debug in REPL
            k.send(Keycode.BACKSPACE)
            time.sleep(0.1)

        if not button_2.value:
            kl.write("Bluefruit")  # use keyboard_layout for words
            time.sleep(0.4)

        if not button_3.value:
            k.send(Keycode.SHIFT, Keycode.L)  # add shift modifier
            time.sleep(0.4)

        if not button_4.value:
            kl.write("e")
            time.sleep(0.4)

        if not button_5.value:
            k.send(Keycode.ENTER)
            time.sleep(0.4)

    ble.start_advertising(advertisement)

Pairing and Bonding

One of the more advance features used in this project is BLE bonding.

When the Central (your mobile device or computer) connects with the Peripheral (the CPB), you will be asked on the mobile device or computer if you want to Pair with the Feather. Once you agree to pair, a bonding process takes place.

During bonding, encrypted keys are exchanged between the two devices and saved away for use the next time the devices attempt to connect. Since they are bonded, the two will connect automatically without asking for a pairing confirmation. This is really convenient, because it means you can walk one of the devices out of range, thus dropping the connection, and when you return, the two devices will re-connect as if nothing ever happened!

This guide was first published on Jan 22, 2020. It was last updated on Jan 22, 2020.

This page (BLE Keyboard Buttons Libraries and Code) was last updated on Apr 22, 2021.

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