qmk-firmware/docs/features/bootmagic.md

Bootmagic

The Bootmagic feature that only handles jumping into the bootloader. This is great for boards that don't have a physical reset button, giving you a way to jump into the bootloader

On some keyboards Bootmagic is disabled by default. If this is the case, it must be explicitly enabled in your rules.mk with:

BOOTMAGIC_ENABLE = yes

Additionally, you may want to specify which key to use. This is especially useful for keyboards that have unusual matrices. To do so, you need to specify the row and column of the key that you want to use. Add these entries to your config.h file:

#define BOOTMAGIC_ROW 0
#define BOOTMAGIC_COLUMN 1

By default, these are set to 0 and 0, which is usually the "ESC" key on a majority of keyboards.

And to trigger the bootloader, you hold this key down when plugging the keyboard in. Just the single key.

::: warning Using Bootmagic will always reset the EEPROM, so you will lose any settings that have been saved. :::

Split Keyboards

When handedness is predetermined via options like SPLIT_HAND_PIN or EE_HANDS, you might need to configure a different key between halves. To identify the correct key for the right half, examine the split key matrix defined in the <keyboard>.h file, e.g.:

#define LAYOUT_split_3x5_2( \
        L01, L02, L03, L04, L05,   R01, R02, R03, R04, R05, \
        L06, L07, L08, L09, L10,   R06, R07, R08, R09, R10, \
        L11, L12, L13, L14, L15,   R11, R12, R13, R14, R15, \
                       L16, L17,   R16, R17                 \
    ) \
    { \
        { L01, L02, L03, L04, L05 }, \
        { L06, L07, L08, L09, L10 }, \
        { L11, L12, L13, L14, L15 }, \
        { L16, L17, KC_NO, KC_NO, KC_NO }, \
        { R01, R02, R03, R04, R05 }, \
        { R06, R07, R08, R09, R10 }, \
        { R11, R12, R13, R14, R15 }, \
        { R16, R17, KC_NO, KC_NO, KC_NO }  \
    }

If you pick the top right key for the right half, it is R05 on the top layout. Within the key matrix below, R05 is located on row 4 columnn 4. To use that key as the right half's Bootmagic trigger, add these entries to your config.h file:

#define BOOTMAGIC_ROW_RIGHT 4
#define BOOTMAGIC_COLUMN_RIGHT 4

::: tip These values are not set by default. :::

Advanced Bootmagic

The bootmagic_scan function is defined weakly, so that you can replace this in your code, if you need. A great example of this is the Zeal60 boards that have some additional handling needed.

To replace the function, all you need to do is add something like this to your code:

void bootmagic_scan(void) {
    matrix_scan();
    wait_ms(DEBOUNCE * 2);
    matrix_scan();

    if (matrix_get_row(BOOTMAGIC_ROW) & (1 << BOOTMAGIC_COLUMN)) {
      // Jump to bootloader.
      bootloader_jump();
    }
}

You can define additional logic here. For instance, resetting the EEPROM or requiring additional keys to be pressed to trigger Bootmagic. Keep in mind that bootmagic_scan is called before a majority of features are initialized in the firmware.

Addenda

To manipulate settings that were formerly configured through the now-deprecated full Bootmagic feature, see Magic Keycodes.

The Command feature, formerly known as Magic, also allows you to control different aspects of your keyboard. While it shares some functionality with Magic Keycodes, it also allows you to do things that Magic Keycodes cannot, such as printing version information to the console. For more information, see Command.