QMK Firmware is an open-source keyboard firmware based on the tmk_keyboard firmware with some useful features for Atmel AVR and ARM controllers. It powers many custom and DIY keyboards, offering extensive customization options and a vibrant community of contributors.

Pros

• Highly customizable, allowing users to create complex layouts and macros
• Supports a wide range of keyboards and microcontrollers
• Active community with frequent updates and contributions
• Extensive documentation and resources for users and developers

Cons

• Steep learning curve for beginners, especially those new to programming
• Requires command-line knowledge and comfort with text editors
• Can be overwhelming due to the vast number of features and options
• Firmware flashing process can be risky if not done correctly

Code Examples

1. Defining a simple keymap:

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    [0] = LAYOUT(
        KC_ESC,  KC_Q,    KC_W,    KC_E,    KC_R,    KC_T,
        KC_TAB,  KC_A,    KC_S,    KC_D,    KC_F,    KC_G,
        KC_LSFT, KC_Z,    KC_X,    KC_C,    KC_V,    KC_B
    )
};

2. Creating a custom macro:

bool process_record_user(uint16_t keycode, keyrecord_t *record) {
    switch (keycode) {
        case CUSTOM_MACRO:
            if (record->event.pressed) {
                SEND_STRING("Hello, QMK!");
            }
            return false;
    }
    return true;
}

3. Implementing a layer toggle:

const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
    [0] = LAYOUT(
        KC_A,    KC_B,    KC_C,
        KC_D,    KC_E,    MO(1)
    ),
    [1] = LAYOUT(
        KC_1,    KC_2,    KC_3,
        KC_4,    KC_5,    KC_TRNS
    )
};

Getting Started

1. Clone the QMK repository:

   git clone https://github.com/qmk/qmk_firmware.git
   

2. Set up your environment:

   cd qmk_firmware
   ./util/qmk_install.sh
   

3. Create a new keyboard firmware:

   qmk new-keyboard
   

4. Customize your keymap in the generated keymap.c file.

5. Compile and flash your firmware:

   qmk compile -kb your_keyboard -km your_keymap
   qmk flash -kb your_keyboard -km your_keymap