qmk_firmware/docs/feature_potentiometers.md

Potentiometers

Add this to your rules.mk:

POTENTIOMETER_ENABLE = yes

and this to your config.h:

#define POTENTIOMETER_PINS { B0 }

Callbacks

The callback functions can be inserted into your <keyboard>.c:

bool potentiometer_update_kb(uint8_t index, uint16_t value) {
    if (!potentiometer_update_user(index, value)) {
        midi_send_cc(&midi_device, 2, 0x3E, 0x7F + value);
    }
    return true;
}

or keymap.c:

bool potentiometer_update_user(uint8_t index, uint16_t value) {
    midi_send_cc(&midi_device, 2, 0x3E, 0x7F + value);
    return false;
}