Watchdog

A watchdog timer automatically resets the system if your application stops responding — useful as a safety net against firmware bugs, deadlocks, or peripheral hangs that would otherwise leave the device stuck. The watchdog counts down from a configured timeout, and your application must kick it periodically (Reset()) to prevent the count from reaching zero. If it reaches zero, the system reboots.

NuGet package: GHIElectronics.TinyCLR.Devices.Watchdog.

warning

Once the watchdog is enabled, it cannot be disabled without a full system reset or power cycle. Plan the timeout carefully before enabling.

warning

Don't enable the watchdog while step-debugging — the system will reset every time you pause on a breakpoint. Either disable the call during development or wrap it in a debug-vs-release conditional.

Basic usage

Run the watchdog in its own thread so the timeout is independent of what your main loop is doing. The example below sets a 5-second timeout and kicks the watchdog every 4 seconds — giving the system a 1-second margin before it would reset.

using GHIElectronics.TinyCLR.Devices.Watchdog;
using System.Threading;

new Thread(RunWatchdog).Start();

void RunWatchdog() {
    var watchdog = WatchdogController.GetDefault();
    watchdog.Enable(5000);      // 5-second timeout.

    while (true) {
        watchdog.Reset();       // Kick the watchdog.
        Thread.Sleep(4000);     // Run again before the timeout expires.
    }
}

Picking a timeout

The timeout has to be longer than the worst-case time between kicks, or you'll false-trip and reboot in normal operation. Things that affect this:

• Worst-case work in the kicking thread between Reset() calls
• GC pauses (occasional, hundreds of ms in heavy workloads)
• Slow blocking operations (file I/O, network requests)

A common pattern is to set the timeout to roughly 2× your steady-state kick interval so transient delays don't trip it, but real hangs do.

If you set it too short, the device gets stuck in a reset loop. If you set it too long, the system might be unresponsive for a long time before recovering. Tune to your application's responsiveness budget.

API reference

Namespace	Description
GHIElectronics.TinyCLR.Devices.Watchdog	Watchdog timer controller classes