• main

      • Low Power

      RMK supports low-power mode by utilizing embassy's low-power feature and the Wait trait in embedded-hal-async.

      Usage

      By default, RMK uses a busy-loop for matrix scanning, which is not very power efficient. To enable the low-power mode, add the async_matrix feature to your Cargo.toml:

      rmk = { version = "...", features = [
    "nrf52840_ble",
    "async_matrix",
] }

      If you're using nRF chips or RP2040, you're all set! Your keyboard is now running in low-power mode. The async_matrix feature enables interrupt-based input detection, and puts your microcontroller into sleep mode when no keys are being pressed.

      For STM32, there are some limitations about EXTI (see here):

      EXTI is not built into Input itself because it needs to take ownership of the corresponding EXTI channel, which is a limited resource.

      Pins PA5, PB5, PC5… all use EXTI channel 5, so you can’t use EXTI on, say, PA5 and PC5 at the same time.

      There are a few more things that you need to do:

      1. Enable the exti feature for your embassy-stm32 dependency in Cargo.toml
      2. Ensure that your input pins don't share the same EXTI channel
      3. For configuration:
        • If you're using keyboard.toml, you are all set. The [rmk_keyboard] macro will automatically check your Cargo.toml and handle it for you.
        • If you're using Rust code, you'll need to use ExtiInput for your input pins:
          let pd9 = ExtiInput::new(p.PD9,  p.EXTI9, Pull::Down);
    let pd8 = ExtiInput::new(p.PD8,  p.EXTI8, Pull::Down);
    let pb13 = ExtiInput::new(p.PB13, p.EXTI13, Pull::Down);
    let pb12 = ExtiInput::new(p.PB12, p.EXTI12, Pull::Down);
    let row_pins = [pd9, pd8, pb13, pb12];

    let mut matrix = Matrix::<_, _, _, ROW, COL, true>::new(row_pins, col_pins, debouncer);

      External VCC

      Some boards, such as the nice!nano have an external 3.3V regulator that can be used to power the LEDs. If not used, the regulator can be disabled by pulling P0_13 low to safe power.

      In the case of the nice!nano, this can be done by adding the following line to main.rs

          // Disable external voltage regulator
    Output::new(peripherals.P0_13, Level::Low, OutputDrive::Standard).persist();

      or the following snippet to your keyboard.toml:

      [[output]]
pin = "P0_13"
initial_state_active = false