While keyboards usually ship with a keymap programmed in, to be able to change that keymap, without flashing new firmware, we need a way to place the keymap into a place we can update at run-time, and which persists across reboots. Fortunately, we have a bit of EEPROM on the keyboard, and can use it to store either the full keymap (and saving space in the firmware then), or store an overlay there. In the latter case, whenever there is a non-transparent key on the overlay, we will use that instead of the keyboard default.

In short, this plugin allows us to change our keymaps, without having to compile and flash new firmware. It does so through the use of the Focus plugin.

Using the plugin

Using the plugin is reasonably simple: after including the header, enable the plugin, and let the Layer object know that we'll be using EEPROMKeymap to figure out which keys to use. We can either use the getKeyOverride or the getKey method, depending on whether we want to override, or fully replace the built-in keymap. Then we need to set at most how many layers we want to store in EEPROM, and that is about it.

We can then update the keymap via Focus.

{c++}
#include <Kaleidoscope.h>
#include <Kaleidoscope-EEPROM-Keymap.h>
#include <Kaleidoscope-EEPROM-Settings.h>
#include <Kaleidoscope-Focus.h>
void setup() {
  Serial.begin(9600);
  Kaleidoscope.use(&EEPROMKeymap, &Focus);
  Kaleidoscope.setup();
  Focus.addHook(FOCUS_HOOK_KEYMAP);
  Focus.addHook(FOCUS_HOOK_KEYMAP_TRANSFER);
  Layer.getKey = EEPROMKeymap.getKeyOverride;
  EEPROMKeymap.max_layers(1);
  EEPROMSettings.seal();
}

Plugin methods

The plugin provides the EEPROMKeymap object, which has the following methods:

`.max_layers(max)`

Tells the extension to reserve space in EEPROM for up to max layers. Can only be called once, any subsequent call will be a no-op.

Focus commands

The plugin provides two Focus hooks: FOCUS_HOOK_KEYMAP, and FOCUS_HOOK_KEYMAP_TRANSFER. Together, they make the following commands available, respectively:

`keymap.map [codes...]`

Without arguments, displays the keymap currently in effect. Each key is printed as its raw, 16-bit keycode.

With arguments, it stores as many keys as given. One does not need to set all keys, on all layers: the command will start from the first key on the first layer, and go on as long as it has input. It will not go past the layer set via the .max_layers() method.

`keymap.transfer LAYER`

Transfers the LAYER from the built-in memory of the keyboard into EEPROM storage.

Useful mostly when one wants to remove the built-in keymap, and wants to easily transfer it into EEPROM first.

This is generally not needed, and it is recommended to not enable this command, unless the feature this command implements is truly needed.