#Watchdog

A hardware watchdog resets the MCU when the firmware stops feeding it in time, recovering the keyboard from a hang without a physical unplug. RMK feeds the watchdog from a dedicated Embassy task.

Because all Runnable tasks are joined cooperatively, a tight-loop stall in any sibling task (for instance: matrix scan, USB, BLE) blocks the watchdog task from feeding, so the timeout expires and the hardware resets the MCU.

The watchdog feature is enabled by default, no user configuration is required.

Supported chips: RP2040, nRF52 (BLE and dfu_nrf builds; the nRF54L series is not yet covered), ESP32 (see rmk/src/watchdog). STM32 has no automatic watchdog codegen.

#How it works

• WatchdogFeed is a small trait each chip implements to feed its hardware timer.
• WatchdogRunner<W> wraps a WatchdogFeed and calls feed() on a fixed interval.
• rmk-macro generates chip-specific init code and joins a watchdog_runner.run() task alongside the keyboard and matrix tasks.
• Rp2040Watchdog and Nrf52Watchdog provide a default_runner(); for ESP32 the generated code configures the MWDT and wraps it in a WatchdogRunner directly. The timeout/feed interval pairs:

#Adding support for other chips

WatchdogFeed and WatchdogRunner are public, so downstream consumers using the Rust API aren't limited to the chips rmk-macro generates code for. Implement WatchdogFeed for your chip's watchdog peripheral, build a WatchdogRunner around it, and pass it to run_all! alongside your other tasks.