CircuitPython code for a TADA-68 style keyboard with a Raspberry Pi Pico controller.

code.py

# Copyright wulfboy_95 2021, All Rights Reserved.

# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.  This file is offered as-is,
# without any warranty.

import board
import digitalio
import struct
import usb_hid

#from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode

# Create and init keyboard USB HID device.
keeb = None
for dev in list(usb_hid.devices):
    if ((dev.usage == 0x06) and
        (dev.usage_page == 0x01) and
        hasattr(dev, "send_report")):
        keeb = dev
if keeb == None:
    raise Exception("Device cannot be found")

# 2D list to convert keyboard matrix to keycode
matrix = [
    [
        Keycode.ESCAPE, Keycode.ONE, Keycode.TWO, Keycode.THREE, Keycode.FOUR,
        Keycode.FIVE, Keycode.SIX, Keycode.SEVEN, Keycode.EIGHT, Keycode.NINE,
        Keycode.ZERO, Keycode.MINUS, Keycode.EQUALS, Keycode.BACKSPACE,
        Keycode.GRAVE_ACCENT
    ],
    [
        Keycode.TAB, Keycode.Q, Keycode.W, Keycode.E, Keycode.R, Keycode.T,
        Keycode.Y, Keycode.U, Keycode.I, Keycode.O, Keycode.P,
        Keycode.LEFT_BRACKET, Keycode.RIGHT_BRACKET, Keycode.BACKSLASH,
        Keycode.DELETE
    ],
    [
        Keycode.CAPS_LOCK, Keycode.A, Keycode.S, Keycode.D, Keycode.F,
        Keycode.G, Keycode.H, Keycode.J, Keycode.K, Keycode.L,
        Keycode.SEMICOLON, Keycode.QUOTE, Keycode.RETURN, Keycode.ENTER,
        Keycode.PAGE_UP
    ],
    [
        Keycode.LEFT_SHIFT, Keycode.SHIFT, Keycode.Z, Keycode.X, Keycode.C,
        Keycode.V, Keycode.B, Keycode.N, Keycode.M, Keycode.COMMA,
        Keycode.PERIOD, Keycode.FORWARD_SLASH, Keycode.RIGHT_SHIFT,
        Keycode.UP_ARROW, Keycode.PAGE_DOWN
    ],
    [
        Keycode.LEFT_CONTROL, Keycode.LEFT_GUI, Keycode.LEFT_ALT,
        Keycode.SPACE, Keycode.SPACE, Keycode.SPACE, Keycode.SPACEBAR,
        Keycode.SPACE, Keycode.SPACE, Keycode.RIGHT_ALT, Keycode.RIGHT_GUI,
        Keycode.RIGHT_CONTROL, Keycode.LEFT_ARROW, Keycode.DOWN_ARROW,
        Keycode.RIGHT_ARROW
    ],
] # matrix[row][col]

input_pins = (board.GP6, board.GP7, board.GP8, board.GP9,board.GP10) # 5 input rows

input_pin_array = [] # DigitalIO array for inputs.

output_pins = (
    board.GP11, board.GP12, board.GP13, board.GP14, board.GP15,
    board.GP16, board.GP17, board.GP18, board.GP19, board.GP20,
    board.GP21, board.GP22, board.GP26, board.GP27, board.GP28
) # 15 output columns

output_pin_array = [] # DigitalIO array for outputs.

# Initialise DigitalIO pins.
for pin in input_pins:
    key_pin = digitalio.DigitalInOut(pin)
    key_pin.direction = digitalio.Direction.INPUT
    key_pin.pull = digitalio.Pull.DOWN
    input_pin_array.append(key_pin)

for pin in output_pins:
    key_pin = digitalio.DigitalInOut(pin)
    key_pin.direction = digitalio.Direction.OUTPUT
    key_pin.drive_mode = digitalio.DriveMode.PUSH_PULL
    output_pin_array.append(key_pin)
           
keys_pressed = [] # list for possible n-key rollover upgrade in the future.
report_array = [0x00] * 8

while True:
    for col in range(len(output_pin_array)):
        output_pin_array[col].value = True # Turn on column pin.
        for row in range(len(input_pin_array)):
            if (matrix[row][col] >= 0xE0) and (input_pin_array[row].value): # Check if modifier is pressed
                report_array[0] |= Keycode.modifier_bit(matrix[row][col]) # Add modifier bit to report.
            elif input_pin_array[row].value: # Check if key is pressed.
                keys_pressed.append(matrix[row][col])
        output_pin_array[col].value = False # Turn off column pin.
    if len(keys_pressed) > 6: # Check for Rollover Error
        for i in range(2,8):
            report_array[i] = 0x01 # Add Rollover Error keycode*6 to report.
    else:
        for i in range(6):
            report_array[i+2] = keys_pressed[i] if i < len(keys_pressed) else 0 # Add keycode to report.
    keeb.send_report(struct.pack("8B",*report_array))
    report_array = [0x00] * 8
    keys_pressed = []

That would be amazing! Thank you! I'm making an oversized keyboard for my grandad who has shaky hands. The next step is to program some buttons to be hotkeys to his favorite websites/applicaitons like facebook and the news. Need to figure out how to get the keycodes to work first though. I'll post it here - let me know if there is a better way to share it. Like I said, total noob.

Thank you again!

# Copyright wulfboy_95 2021, All Rights Reserved.

# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.  This file is offered as-is,
# without any warranty.

import board
import digitalio
import struct
import usb_hid

#from adafruit_hid.keyboard import Keyboard
from adafruit_hid.keycode import Keycode

# Create and init keyboard USB HID device.
keeb = None
for dev in list(usb_hid.devices):
    if ((dev.usage == 0x06) and
        (dev.usage_page == 0x01) and
        hasattr(dev, "send_report")):
        keeb = dev
if keeb == None:
    raise Exception("Device cannot be found")

# 2D list to convert keyboard matrix to keycode - SKIP ROW 1 FOR NOW - THOSE WILL BE THE HOTKEYS
matrix = [
    [
        Keycode.ESCAPE, Keycode.ONE, Keycode.TWO, Keycode.THREE, Keycode.FOUR,
        Keycode.FIVE, Keycode.SIX, Keycode.SEVEN, Keycode.EIGHT, Keycode.NINE,
        Keycode.ZERO, Keycode.MINUS, Keycode.EQUALS, Keycode.BACKSPACE
    ],
    [
        Keycode.ONE, Keycode.TWO, Keycode.THREE, Keycode.FOUR, Keycode.FIVE, Keycode.SIX,
        Keycode.SEVEN, Keycode.EIGHT, Keycode.NINE, Keycode.ZERO
    ],
    [
        Keycode.Q, Keycode.W, Keycode.E, Keycode.R, Keycode.T,
        Keycode.Y, Keycode.U, Keycode.I, Keycode.O, Keycode.P
    ],
    [
        Keycode.CAPS_LOCK, Keycode.A, Keycode.S, Keycode.D, Keycode.F,
        Keycode.G, Keycode.H, Keycode.J, Keycode.K, Keycode.L
    ],
    [
        Keycode.QUOTE, Keycode.Z, Keycode.X, Keycode.C,
        Keycode.V, Keycode.B, Keycode.N, Keycode.M, Keycode.COMMA,
        Keycode.UP_ARROW, Keycode.ENTER
    ],
    [
        Keycode.COMMA, Keycode.PERIOD, Keycode.FORWARD_SLASH,
        Keycode.TAB, Keycode.SPACEBAR, Keycode.SPACEBAR, Keycode.BACKSPACE, Keycode.LEFT_ARROW,
        Keycode.DOWN_ARROW, Keycode.RIGHT_ARROW
    ],
] # matrix[row][col]

input_pins = (board.GP5,board.GP6, board.GP7, board.GP8, board.GP9,board.GP10) # 6 input rows - ** added one input pin - board.gp5

input_pin_array = [] # DigitalIO array for inputs.

output_pins = (
    board.GP11, board.GP12, board.GP13, board.GP14, board.GP15,
    board.GP16, board.GP17, board.GP18, board.GP19, board.GP20,
    board.GP21, board.GP22, board.GP26, board.GP27
) # 14 output columns - ** DELETED GP28

output_pin_array = [] # DigitalIO array for outputs.

# Initialise DigitalIO pins.
for pin in input_pins:
    key_pin = digitalio.DigitalInOut(pin)
    key_pin.direction = digitalio.Direction.INPUT
    key_pin.pull = digitalio.Pull.DOWN
    input_pin_array.append(key_pin)

for pin in output_pins:
    key_pin = digitalio.DigitalInOut(pin)
    key_pin.direction = digitalio.Direction.OUTPUT
    key_pin.drive_mode = digitalio.DriveMode.PUSH_PULL
    output_pin_array.append(key_pin)
           
keys_pressed = [] # list for possible n-key rollover upgrade in the future.
report_array = [0x00] * 8

while True:
    for col in range(len(output_pin_array)):
        output_pin_array[col].value = True # Turn on column pin.
        for row in range(len(input_pin_array)):
            if (matrix[row][col] >= 0xE0) and (input_pin_array[row].value): # Check if modifier is pressed
                report_array[0] |= Keycode.modifier_bit(matrix[row][col]) # Add modifier bit to report.
            elif input_pin_array[row].value: # Check if key is pressed.
                keys_pressed.append(matrix[row][col])
        output_pin_array[col].value = False # Turn off column pin.
    if len(keys_pressed) > 6: # Check for Rollover Error
        for i in range(2,8):
            report_array[i] = 0x01 # Add Rollover Error keycode*6 to report.
    else:
        for i in range(6):
            report_array[i+2] = keys_pressed[i] if i < len(keys_pressed) else 0 # Add keycode to report.
    keeb.send_report(struct.pack("8B",*report_array))
    report_array = [0x00] * 8
    keys_pressed = []

That would be amazing! Thank you! I'm making an oversized keyboard for my grandad who has shaky hands. The next step is to program some buttons to be hotkeys to his favorite websites/applicaitons like facebook and the news. Need to figure out how to get the keycodes to work first though. I'll post it here - let me know if there is a better way to share it. Like I said, total noob.

Thank you again!

I've just looked at your code. The problem appears to be caused by having a lower number of elements in some rows within the matrix list than the number of columns. You should pad these rows with placeholder keycodes.

Very helpful, thank you! I have adjusted the code and I'm no longer getting an error when I run it. I'll try it out with my keyboard when I get home tonight.

Do you have any ideas on how to use keypresses in the first row as hotkeys to open websites in a browser? I was thinking I could just use webbrowser, but it seems like that's not included in the circuitpython library.

No pressure of course, but if you had any thoughts, they would be greatly appreciated.

Thanks again!

@wulfboy-95 The keypad.KeyMatrix module added in recent versions of CircuitPython does matrix scanning, which you are doing "by hand" now. See https://learn.adafruit.com/key-pad-matrix-scanning-in-circuitpython/keymatrix. You'll want to read the whole guide for background.

(Referred here by a mention of your code in https://forums.adafruit.com/viewtopic.php?f=60&t=193075&p=934045#p934029)

@dhalbert Thanks! I'll check it out.

I've written a new version of this code which uses the keypad.KeyMatrix module and has fewer lines of code. Make sure you've flashed CircuitPython 7.x.x (or newer) on your Pico before using it.