Low-power

RMK supports low-power mode by using utilizing embassy's low-power feature and Wait trait in embedded-hal-async. To enable low-power mode, add async_matrix feature to your Cargo.toml:

rmk = { version = "0.4", features = [
     "nrf52840_ble",
+    "async_matrix",
] }

If you're using nRF chips or rp2040, you're all set! You've already got your keyboard running in low-power mode.

For stm32, there's 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 have to do:

1. Enable exti feature of your embassy-stm32 dependency

2. Ensure that your input pins don't share same EXTI channel

3. If you're using keyboard.toml, nothing more to do. The [rmk_keyboard] macro will check your Cargo.toml and do the work for you. But if you're using Rust code, you need to use ExtiInput as your input pins, and update generics type of RMK keyboard run:

#![allow(unused)]
fn main() {
    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 input_pins = [pd9, pd8, pb13, pb12];

    let mut matrix = Matrix::<_, _, _, ROW, COL>::new(input_pins, output_pins, debouncer);
}