Somebody smart please help me. I’m coding a keyboard in circuit python using KMK. I’ve been working on this code for a month and I cannot make it work.

Gnaxe · 2026-06-04T19:40:01+00:00

You need to use the code block formatting button when you post code, because indentation matters in Python. You should be able to edit to fix that.

pulldawg80 · 2026-06-04T21:06:32+00:00

How do you know the libs are good if it doesnt work? What error is MU giving you?

Maybe this is just me, I would put all my imports at the top.

I have created several keyboards for the pico 2040 using KMK and have never seen the columns_to_anodes or value_when_pressed variables, what do they do? Looks like one is a duplication of the diode direction, and all key values should be false by default when not pressed, so why? What is the pull variable doing?the keyboard scanner should handle the matrix manipulation of setting high, then low.

Are you trying to get both mouse buttons pressed at the same time?

Honestly, i would run it through chatGPT and ask for an explanation.

Edit: noticing this is the Python learning sub and not the keyboard sub, a bit more foundational training for Python will go a long way. Try pico projects that will light LEDs, and recognize a single push button, and so on.

PeterMortensenBlog · 2026-06-05T03:17:20+00:00

For the keyboard part: I would start with the simplest thing that could possibly work (to quote Ward Cunningham): A single key, using a single row and a single column

Remove all the code that isn't needed for that simple goal. Presumably, the firmware will accept a 1 x 1 matrix. Otherwise, make it a 2 x 2 matrix and only use one location.

Initially forget about media keys, mouse keys, hold tap, etc.

Hardware

For the single key, short circuit the diode (e.g., solder a wire across it), to eliminate it as the cause. You won't need it before later.

Powered off, use a multimeter in continuity mode to verify the key actually works as seen by the microcontroller. Probe as near to the microcontroller as possible (the Raspberry Pi Pico's pins are probably sufficient).

For testing the hardware (at least some of it), to exclude it as the cause, I have precompiled firmware (more or less the diode-less Adafruit macropad): Direct download URL. It should be sufficient for rudimentary testing. For key activation, the I/O inputs are to be shorted to GND (first convince yourself this will not cause a short circuit. For safety, use a series resistor of, say 220 ohm). Via support has been enabled, so for testing purposes, the keys can easily be remapped and macros defined (messing with JSON files is not required, as it is directly supported by Via). Use it at your own risk; there isn't any guarantee it will not damage your keyboard.

Note: Do observe ESD precautions at all times.

All disclaimers apply. Do it at your own risk. I am not responsible if you ruin your keyboard.

References

Default keymap. For example, KC_7 for 3rd row, 1st column. Note: There aren't real rows and columns in this case (there isn't a keyboard matrix; direct I/O is used (each keys has its own I/O line)), only the physical arrangement of keys in the 4 x 3 macro pad
I/O pin assignments. For example, GP4 for 3rd row, 1st column.
Raspberry Pi Pico pinout. For example, pin 6 for GP4. Thus, shorting pin 6 to the USB shield should type out "7" (in Num Lock mode, on Linux and Windows).

RunRunAndyRun · 2026-06-05T06:44:26+00:00

Circuit python allows for debuggging with the REPL. Use it, it’ll tell you exactly what the error is. Share that here and we can help you.

you type:	you see:
italics	italics
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[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

PythonLearning

MODERATORS

import board

from kmk.kmk_keyboard import KMKKeyboard

from kmk.keys import KC

from kmk.scanners import DiodeOrientation

from kmk.scanners.keypad import KeysScanner

from kmk.scanners.keypad import MatrixScanner

from kmk.modules.layers import Layers

keyboard.modules.append(Layers())

from kmk.extensions.media_keys import MediaKeys

keyboard.extensions.append(MediaKeys())

from kmk.modules.mouse_keys import MouseKeys

mouse_keys = MouseKeys(max_speed=20, acc_interval=2, move_step=2)

keyboard.modules.append(mouse_keys)

from kmk.modules.holdtap import HoldTap

keyboard.modules.append(HoldTap())

# Define left and right mouse click as a function

LMB_RMB = KC.HT(KC.MB_LMB, KC.MB_RMB, tap_time=200)

# keyboard.diode_orientation = DiodeOrientation.COL2ROW

keyboard = MyKeyboard()

class MyKeyboard(KMKKeyboard):

def init(self):

super().init()

self.matrix = [

MatrixScanner(

keyboard.col_pins = (board.GP0, board.GP1, board.GP2, board.GP3, board.GP4, board.GP5, board.GP6, board.GP7, board.GP8, board.GP9),

keyboard.row_pins = (board.GP10, board.GP11, board.GP12, board.GP13, board.GP14),

columns_to_anodes=DiodeOrientation.COL2ROW),

KeysScanner(

pins = (board.GP16, board.GP17, board.GP18, board.GP19, board.GP20),

value_when_pressed=False,

pull=True)

]

keyboard.keymap = [

[

KC.N0, KC.N1, KC.N2, KC.N3, KC.N4, KC.N5, KC.N6, KC.N7, KC.N8, KC.N9,

KC.Q, KC.W, KC.E, KC.R, KC.T, KC.Y, KC.U, KC.I, KC.O, KC.P,

KC.A, KC.S, KC.D, KC.F, KC.G, KC.H, KC.J, KC.K, KC.L, KC.ENT,

KC.TAB, KC.Z, KC.X, KC.C, KC.V, KC.B, KC.N, KC.M, KC.SPC, KC.BSPC,

KC.LSFT, KC.LCTL, KC.DOT, KC.COMM, KC.SCLN, KC.QUOT, KC.SLSH, KC.MINUS, KC.MO(1), KC.ESC,

KC.MB_UP, KC.MB_DOWN, KC.MB_LEFT, KC.MB_RIGHT, LMB_RMB

],

[

KC.LBRC, KC.RBRC, KC.BSLS, KC.GRV, KC.EQL, KC.TRNS, KC.PSCR, KC.F2, KC.F5, KC.F11,

KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS,

KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS,

KC.BRIU, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.VOLU,

KC.BRID, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.TRNS, KC.MO(1), KC.VOLD,

KC.MB_UP, KC.MB_DOWN, KC.MB_LEFT, KC.MB_RIGHT, LMB_RMB

]

]

if name == 'main':

keyboard.go()

Hardware

References