FAQ#

My matrix is row2col, the matrix doesn't work#

RMK uses col2row as the default matrix diode direction. To use the row2col matrix, you can add row2col = true under the [matrix] section or [split.central.matrix] section:

# keyboard.toml
[matrix]
row2col = true

# Or
[split.central.matrix]
row2col = true

If you're using Rust code, set the generics value COL2ROW to false to make the matrix row2col:

// col2row matrix
let mut matrix = Matrix::<_, _, _, ROW, COL, true>::new(row_pins, col_pins, debouncer);
// row2col matrix
let mut matrix = Matrix::<_, _, _, ROW, COL, false>::new(row_pins, col_pins, debouncer);

Where is my built firmware?#

By default, the built firmware is at target/<TARGET>/<MODE> folder, where <TARGET> is your microcontroller's target and <MODE> is debug or release, depending on your build mode.

The firmware's name is your project name in Cargo.toml. It's actually an elf file, but without file extension.

I want hex/bin/uf2 file, how can I get it?#

By default, Rust compiler generates elf file in target folder. There're a little extra steps for generating hex, bin or uf2 file.

• hex/bin: To generate hex/bin file, you need cargo-binutils. You can use

  cargo install cargo-binutils rustup component add llvm-tools

  to install it. Then, you can use the following command to generate hex or bin firmware:

  # Generate .bin file cargo objcopy --release -- -O binary rmk.bin # Generate .hex file cargo objcopy --release -- -O ihex rmk.hex

• uf2: RMK provides cargo-make config for all examples to generate uf2 file automatically. Check Makefile.toml files in the example folders. The following command can be used to generate uf2 firmware:

  # Install cargo-make
  cargo install --force cargo-make
  
  # Generate uf2
  cargo make uf2 --release

I changed the keymap in keyboard.toml, but the keyboard is not updated#

RMK assumes that users change the keymap using vial. So reflashing the firmware won't change the keymap by default. For testing scenarios, RMK provides a config clear_storage under the [storage] section. You can enable it to clear the storage when the keyboard boots.

[storage]
# Set `clear_storage` to true to clear all the stored info when the keyboard boots
clear_storage = true

Note that the storage will be cleared EVERY TIME you reboot the keyboard.

rust-lld: error: section will not fit in region 'FLASH': overflowed by x bytes#

This is because your MCU's flash is too small. Try building in release mode: cargo build --release. If the error persists, follow our binary size optimization documentation to reduce your code size.

Unable to find libclang#

On Windows machines, you may get the following error when building the firmware:

That's because you don't have LLVM (Clang) installed, or the system doesn't know the path to the installed LLVM (Clang). You can try the solution here: https://rust-lang.github.io/rust-bindgen/requirements.html#windows

Unable to generate bindings: NotExist#

On Windows machines, you may get the following error when building the firmware:

To resolve this, you need to enable git symlink on Windows:

git config --global core.symlinks true

I can see an RMK Start log, but nothing else#

First, you need to check the RCC config of your board. Make sure that the USB's clock is enabled and set to 48 MHz. For example, if you're using STM32F1, you can set the RCC as follows:

// If you're using a keyboard.toml
#[rmk_keyboard]
mod keyboard {
    use embassy_stm32::{time::Hertz, Config};

    #[Override(chip_config)]
    fn config() -> Config {
        let mut config = Config::default();
        config.rcc.hse = Some(Hse {
            freq: Hertz(8_000_000),
            // Oscillator for bluepill, Bypass for nucleos.
            mode: HseMode::Oscillator,
        });
        config.rcc.pll = Some(Pll {
            src: PllSource::HSE,
            prediv: PllPreDiv::DIV1,
            mul: PllMul::MUL9,
        });
        config.rcc.sys = Sysclk::PLL1_P;
        config.rcc.ahb_pre = AHBPrescaler::DIV1;
        config.rcc.apb1_pre = APBPrescaler::DIV2;
        config.rcc.apb2_pre = APBPrescaler::DIV1;
        config
    }
}

If the keyboard still doesn't work, enable full logging trace in .cargo/config.toml:

[env]
DEFMT_LOG = "trace"

run cargo clean and then cargo run --release. Open an issue with the detailed logs.

I see "ERROR: Storage is full" error in the log#

By default, RMK uses only 2 sectors of your microcontroller's internal flash. You may get the following error if 2 sectors are not big enough to store all your keymaps:

If you have more sectors available in your internal flash, you can increase num_sectors in [storage] section of your keyboard.toml, or change storage_config in your RmkConfig if you're using Rust API.

OUTDATED: panicked at embassy-executor: task arena is full.#

The current Embassy requires manual setting of the task arena size. By default, RMK sets it to 32768 in all examples:

# Cargo.toml
embassy-executor = { version = "0.9", features = [
    "defmt",
    "arch-cortex-m",
    "task-arena-size-32768",
    "executor-thread",
] }

If you get the ERROR panicked at 'embassy-executor: task arena is full.' error after flashing to your MCU, that means you should increase your Embassy's task arena. Embassy has a series of cargo features to do this; for example, changing the task arena size to 65536:

# Cargo.toml
embassy-executor = { version = "0.9", features = [
    "defmt",
    "arch-cortex-m",
-   "task-arena-size-32768",
+   "task-arena-size-65536",
    "executor-thread",
] }

In the latest git version of Embassy, the task arena size can be calculated automatically, but it requires the nightly version of Rust.

If you're comfortable with nightly Rust, you can enable the nightly feature of embassy-executor and remove the task-arena-size-* feature.

What font is used for the RMK logo?#

It's Honk.