keyboard controller firmware for Atmel AVR USB family
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Quantum MK Firmware

This is a keyboard firmware based on the tmk_keyboard firmware with some useful features for Atmel AVR controllers, and more specifically, the OLKB product line and the ErgoDox EZ keyboard.

QMK is developed and maintained by Jack Humbert of OLKB with contributions from the community, and of course, TMK.

This documentation is edited and maintained by Erez Zukerman of ErgoDox EZ. If you spot any typos or inaccuracies, please open an issue.

Important background info: TMK documentation

The documentation below explains QMK customizations and elaborates on some of the more useful features of TMK. To understand the base firmware, and especially what layers are and how they work, please see

Getting started

  • contains instructions to set up a build environment, build the firmware, and deploy it to a keyboard. Once your build environment has been set up, all make commands to actually build the firmware must be run from a folder in keyboard/.
  • If you're looking to customize a keyboard that currently runs QMK or TMK, find your keyboard's directory under keyboard/ and run the make commands from there.
  • If you're looking to apply this firmware to an entirely new hardware project (a new kind of keyboard), you can create your own Quantum-based project by using ./ <project_name>, which will create /keyboard/<project_name> with all the necessary components for a Quantum project.

Makefile Options

You have access to a bunch of goodies! Check out the Makefile to enable/disable some of the features. Uncomment the # to enable them. Setting them to no does nothing and will only confuse future you.

BACKLIGHT_ENABLE = yes # Enable keyboard backlight functionality
MIDI_ENABLE = yes      # MIDI controls
UNICODE_ENABLE = no    # <-- This is how you disable an option, just set it to "no"
BLUETOOTH_ENABLE = yes # Enable Bluetooth with the Adafruit EZ-Key HID

Customizing Makefile options on a per-keymap basis

If your keymap directory has a file called (note the lowercase filename, and the .mk extension), any Makefile options you set in that file will take precedence over other Makefile options (those set for Quantum as a whole or for your particular keyboard).

So let's say your keyboard's makefile has CONSOLE_ENABLE = yes (or maybe doesn't even list the CONSOLE_ENABLE option, which would cause it to revert to the global Quantum default). You want your particular keymap to not have the debug console, so you make a file called and specify CONSOLE_ENABLE = no.

Quick aliases to common actions

Your keymap can include shortcuts to common operations (called "function actions" in tmk).

Switching and toggling layers

MO(layer) - momentary switch to layer. As soon as you let go of the key, the layer is deactivated and you pop back out to the previous layer. When you apply this to a key, that same key must be set as KC_TRNS on the destination layer. Otherwise, you won't make it back to the original layer when you release the key (and you'll get a keycode sent). You can only switch to layers above your current layer. If you're on layer 0 and you use MO(1), that will switch to layer 1 just fine. But if you include MO(3) on layer 5, that won't do anything for you -- because layer 3 is lower than layer 5 on the stack.

LT(layer, kc) - momentary switch to layer when held, and kc when tapped. Like MO(), this only works upwards in the layer stack (layer must be higher than the current layer).

TG(layer) - toggles a layer on or off. As with MO(), you should set this key as KC_TRNS in the destination layer so that tapping it again actually toggles back to the original layer. Only works upwards in the layer stack.

Fun with modifier keys

  • LSFT(kc) - applies left Shift to kc (keycode) - S(kc) is an alias
  • RSFT(kc) - applies right Shift to kc
  • LCTL(kc) - applies left Control to kc
  • RCTL(kc) - applies right Control to kc
  • LALT(kc) - applies left Alt to kc
  • RALT(kc) - applies right Alt to kc
  • LGUI(kc) - applies left GUI (command/win) to kc
  • RGUI(kc) - applies right GUI (command/win) to kc
  • HYPR(kc) - applies Hyper (all modifiers) to kc
  • MEH(kc) - applies Meh (all modifiers except Win/Cmd) to kc
  • LCAG(kc) - applies CtrlAltGui to kc

You can also chain these, like this:

LALT(LCTL(KC_DEL)) -- this makes a key that sends Alt, Control, and Delete in a single keypress.

The following shortcuts automatically add LSFT() to keycodes to get commonly used symbols. Their long names are also available and documented in /quantum/keymap_common.h.

KC_AT    @
KC_DLR   $

MT(mod, kc) - is mod (modifier key - MOD_LCTL, MOD_LSFT) when held, and kc when tapped. In other words, you can have a key that sends Esc (or the letter O or whatever) when you tap it, but works as a Control key or a Shift key when you hold it down.

These are the values you can use for the mod in MT() (right-hand modifiers are not available):


These can also be combined like MOD_LCTL | MOD_LSFT e.g. MT(MOD_LCTL | MOD_LSFT, KC_ESC) which would activate Control and Shift when held, and send Escape when tapped.

We've added shortcuts to make common modifier/tap (mod-tap) mappings more compact:

  • CTL_T(kc) - is LCTL when held and kc when tapped
  • SFT_T(kc) - is LSFT when held and kc when tapped
  • ALT_T(kc) - is LALT when held and kc when tapped
  • GUI_T(kc) - is LGUI when held and kc when tapped
  • ALL_T(kc) - is Hyper (all mods) when held and kc when tapped. To read more about what you can do with a Hyper key, see this blog post by Brett Terpstra
  • LCAG_T(kc) - is CtrlAltGui when held and kc when tapped
  • MEH_T(kc) - is like Hyper, but not as cool -- does not include the Cmd/Win key, so just sends Alt+Ctrl+Shift.

Temporarily setting the default layer

DF(layer) - sets default layer to layer. The default layer is the one at the "bottom" of the layer stack - the ultimate fallback layer. This currently does not persist over power loss. When you plug the keyboard back in, layer 0 will always be the default. It is theoretically possible to work around that, but that's not what DF does.

Prevent stuck modifiers

Consider the following scenario:

  1. Layer 0 has a key defined as Shift.
  2. The same key is defined on layer 1 as the letter A.
  3. User presses Shift.
  4. User switches to layer 1 for whatever reason.
  5. User releases Shift, or rather the letter A.
  6. User switches back to layer 0.

Shift was actually never released and is still considered pressed.

If such situation bothers you add this to your config.h:


This option uses 5 bytes of memory per every 8 keys on the keyboard rounded up (5 bits per key). For example on Planck (48 keys) it uses (48/8)*5 = 30 bytes.

Remember: These are just aliases

These functions work the same way that their ACTION_* functions do - they're just quick aliases. To dig into all of the tmk ACTION_* functions, please see the TMK documentation.

Instead of using FNx when defining ACTION_* functions, you can use F(x) - the benefit here is being able to use more than 32 function actions (up to 4096), if you happen to need them.

Macro shortcuts: Send a whole string when pressing just one key

Instead of using the ACTION_MACRO function, you can simply use M(n) to access macro n - n will get passed into the action_get_macro as the id, and you can use a switch statement to trigger it. This gets called on the keydown and keyup, so you'll need to use an if statement testing record->event.pressed (see keymap_default.c).

const macro_t *action_get_macro(keyrecord_t *record, uint8_t id, uint8_t opt) // this is the function signature -- just copy/paste it into your keymap file as it is.
  switch(id) {
    case 0: // this would trigger when you hit a key mapped as M(0)
      if (record->event.pressed) {
        return MACRO( I(255), T(H), T(E), T(L), T(L), W(255), T(O), END  ); // this sends the string 'hello' when the macro executes
  return MACRO_NONE;

A macro can include the following commands:

  • I() change interval of stroke in milliseconds.
  • D() press key.
  • U() release key.
  • T() type key(press and release).
  • W() wait (milliseconds).
  • END end mark.

So above you can see the stroke interval changed to 255ms between each keystroke, then a bunch of keys being typed, waits a while, then the macro ends.

Note: Using macros to have your keyboard send passwords for you is possible, but a bad idea.

Advanced macro functions

To get more control over the keys/actions your keyboard takes, the following functions are available to you in the action_get_macro function block:

  • record->event.pressed

This is a boolean value that can be tested to see if the switch is being pressed or released. An example of this is

if (record->event.pressed) {
  // on keydown
} else {
  // on keyup
  • register_code(<kc>);

This sends the <kc> keydown event to the computer. Some examples would be KC_ESC, KC_C, KC_4, and even modifiers such as KC_LSFT and KC_LGUI.

  • unregister_code(<kc>);

Parallel to register_code function, this sends the <kc> keyup event to the computer. If you don't use this, the key will be held down until it's sent.

  • layer_on(<n>);

This will turn on the layer <n> - the higher layer number will always take priority. Make sure you have KC_TRNS for the key you're pressing on the layer you're switching to, or you'll get stick there unless you have another plan.

  • layer_off(<n>);

This will turn off the layer <n>.

  • clear_keyboard();

This will clear all mods and keys currently pressed.

  • clear_mods();

This will clear all mods currently pressed.

  • clear_keyboard_but_mods();

This will clear all keys besides the mods currently pressed.

  • update_tri_layer(layer_1, layer_2, layer_3);

If the user attempts to activate layer 1 AND layer 2 at the same time (for example, by hitting their respective layer keys), layer 3 will be activated. Layers 1 and 2 will also be activated, for the purposes of fallbacks (so a given key will fall back from 3 to 2, to 1 -- and only then to 0).

Timer functionality

It's possible to start timers and read values for time-specific events - here's an example:

static uint16_t key_timer;
key_timer = timer_read();
if (timer_elapsed(key_timer) < 100) {
  // do something if less than 100ms have passed
} else {
  // do something if 100ms or more have passed

It's best to declare the static uint16_t key_timer; outside of the macro block (top of file, etc).

Additional keycode aliases for software-implemented layouts (Colemak, Dvorak, etc)

Everything is assuming you're in Qwerty (in software) by default, but there is built-in support for using a Colemak or Dvorak layout by including this at the top of your keymap:

#include <keymap_extras/keymap_colemak.h>

If you use Dvorak, use keymap_dvorak.h instead of keymap_colemak.h for this line. After including this line, you will get access to:

  • CM_* for all of the Colemak-equivalent characters
  • DV_* for all of the Dvorak-equivalent characters

These implementations assume you're using Colemak or Dvorak on your OS, not on your keyboard - this is referred to as a software-implemented layout. If your computer is in Qwerty and your keymap is in Colemak or Dvorak, this is referred to as a firmware-implemented layout, and you won't need these features.

To give an example, if you're using software-implemented Colemak, and want to get an F, you would use CM_F - KC_F under these same circumstances would result in T.

Additional language support

In quantum/keymap_extras/, you'll see various language files - these work the same way as the alternative layout ones do. Most are defined by their two letter country/language code followed by an underscore and a 4-letter abbreviation of its name. FR_UGRV which will result in a ù when using a software-implemented AZERTY layout. It's currently difficult to send such characters in just the firmware (but it's being worked on - see Unicode support).

Unicode support

You can currently send 4 hex digits with your OS-specific modifier key (RALT for OSX with the "Unicode Hex Input" layout) - this is currently limited to supporting one OS at a time, and requires a recompile for switching. 8 digit hex codes are being worked on. The keycode function is UC(n), where n is a 4 digit hexidecimal. Enable from the Makefile.

Other firmware shortcut keycodes

  • RESET - puts the MCU in DFU mode for flashing new firmware (with make dfu)
  • DEBUG - the firmware into debug mode - you'll need hid_listen to see things
  • BL_ON - turns the backlight on
  • BL_OFF - turns the backlight off
  • BL_<n> - sets the backlight to level n
  • BL_INC - increments the backlight level by one
  • BL_DEC - decrements the backlight level by one
  • BL_TOGG - toggles the backlight
  • BL_STEP - steps through the backlight levels

Enable the backlight from the Makefile.

MIDI functionalty

This is still a WIP, but check out quantum/keymap_midi.c to see what's happening. Enable from the Makefile.

Bluetooth functionality

This requires some hardware changes, but can be enabled via the Makefile. The firmware will still output characters via USB, so be aware of this when charging via a computer. It would make sense to have a switch on the Bluefruit to turn it off at will.

International Characters on Windows

AutoHotkey allows Windows users to create custom hotkeys among others.

The method does not require Unicode support in the keyboard itself but depends instead of AutoHotkey running in the background.

First you need to select a modifier combination that is not in use by any of your programs. CtrlAltWin is not used very widely and should therefore be perfect for this. There is a macro defined for a mod-tab combo LCAG_T. Add this mod-tab combo to a key on your keyboard, e.g.: LCAG_T(KC_TAB). This makes the key behave like a tab key if pressed and released immediately but changes it to the modifier if used with another key.

In the default script of AutoHotkey you can define custom hotkeys.

<^<!<#a::Send, ä
<^<!<#<+a::Send, Ä

The hotkeys above are for the combination CtrlAltGui and CtrlAltGuiShift plus the letter a. AutoHotkey inserts the Text right of Send, when this combination is pressed.

RGB Under Glow Mod

Planck with RGB Underglow

Here is a quick demo on Youtube (with NPKC KC60) (

For this mod, you need an unused pin wiring to DI of WS2812 strip. After wiring the VCC, GND, and DI, you can enable the underglow in your Makefile.


Please note that the underglow is not compatible with audio output. So you cannot enable both of them at the same time.

Please add the following options into your config.h, and set them up according your hardware configuration. These settings are for the F4 by default:

#define ws2812_PORTREG  PORTF
#define ws2812_DDRREG   DDRF
#define ws2812_pin PF4
#define RGBLED_NUM 14     // Number of LEDs

You'll need to edit PORTF, DDRF, and PF4 on the first three lines to the port/pin you have your LED(s) wired to, eg for B3 change things to:

#define ws2812_PORTREG  PORTB
#define ws2812_DDRREG   DDRB
#define ws2812_pin PB3

The firmware supports 5 different light effects, and the color (hue, saturation, brightness) can be customized in most effects. To control the underglow, you need to modify your keymap file to assign those functions to some keys/key combinations. For details, please check this keymap. keyboard/planck/keymaps/yang/keymap.c

WS2812 Wiring

WS2812 Wiring

Please note the USB port can only supply a limited amount of power to the keyboard (500mA by standard, however, modern computer and most usb hubs can provide 700+mA.). According to the data of NeoPixel from Adafruit, 30 WS2812 LEDs require a 5V 1A power supply, LEDs used in this mod should not more than 20.

Safety Considerations

You probably don't want to "brick" your keyboard, making it impossible to rewrite firmware onto it. Here are some of the parameters to show what things are (and likely aren't) too risky.

  • If a keyboard map does not include RESET, then, to get into DFU mode, you will need to press the reset button on the PCB, which requires unscrewing some bits.
  • Messing with tmk_core / common files might make the keyboard inoperable
  • Too large a .hex file is trouble; make dfu will erase the block, test the size (oops, wrong order!), which errors out, failing to flash the keyboard
  • DFU tools do /not/ allow you to write into the bootloader (unless you throw in extra fruitsalad of options), so there is little risk there.
  • EEPROM has around a 100000 write cycle. You shouldn't rewrite the firmware repeatedly and continually; that'll burn the EEPROM eventually.