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dxWatchdog

1. Overview​

This module is part of the official dejaOS system module library. It wraps the native watchdog C library and provides a handle-based interface for software and hardware watchdog operations.

What it does: A watchdog timer resets the system if the application stops feeding it within the configured timeout. This helps recover from hangs, deadlocks, or runaway logic in production deployments.

Typical usage:

  • Call watchdog.init() once at startup.
  • Set a global timeout with watchdog.start(timeout_ms).
  • Enable one or more channels with watchdog.enable(chan, true).
  • Call watchdog.restart(chan) periodically from your main loop or a timer (for example every 5 seconds).
  • Call watchdog.stop() and watchdog.deinit() when shutting down cleanly.

The module is designed for multi-threaded environments; different watchdog channels can be operated in parallel.

2. Files​

  • dxWatchdog.js
  • libvbar-m-dxwatchdog.so

Ensure these files are placed under the dxmodules subdirectory in your project root.

3. Dependencies​

  • None

4. Compatible Devices​

Compatible with dejaOS v2.0+ devices that expose watchdog hardware or software watchdog support. Timeout behavior and channel count may vary by device—confirm against your product documentation.

5. Usage​

Basic usage​

import watchdog from "./dxmodules/dxWatchdog.js";
import logger from "./dxmodules/dxLogger.js";
import std from "./dxmodules/dxStd.js";

try {
  watchdog.init();
} catch (e) {
  logger.error("Failed to init watchdog:", e);
}

try {
  const started = watchdog.start(5000);
  logger.info("Watchdog started:", started);

  const isPoweron = watchdog.isPoweron();
  logger.info("Watchdog is poweron:", isPoweron);

  const enabled = watchdog.enable(0, true);
  logger.info("Channel enabled:", enabled);

  const restarted = watchdog.restart(0);
  logger.info("Watchdog restarted:", restarted);

  std.setInterval(() => {
    watchdog.restart(0);
  }, 5000);
} catch (e) {
  logger.error("Watchdog operation failed:", e);
}

// When shutting down cleanly
watchdog.stop();
watchdog.deinit();

Production pattern​

In production apps, keep feeding the watchdog from a stable code path (main loop or dedicated timer). If debugging causes frequent restarts, temporarily disable watchdog logic in sample code—see FAQ.

6. API Reference​

watchdog.TYPE​

Read-only enum for watchdog type:

ConstantValueDescription
SOFTWARE1Software watchdog
HARDWARE2Hardware watchdog

watchdog.init()​

Initialize the watchdog device.

Returns: none

Throws: Error if initialization fails.

watchdog.deinit()​

Release the watchdog device.

Returns: boolean — true on success

watchdog.isPoweron()​

Check whether the watchdog device is powered on.

Returns: boolean

watchdog.start(timeout_ms)​

Start the watchdog timer.

Parameters:

  • timeout_ms (number): Timeout in milliseconds, must be greater than 0, required

Returns: boolean — true on success, false on failure

Throws: Error if timeout_ms is missing or not greater than 0

watchdog.stop()​

Stop the watchdog timer.

Returns: none

watchdog.enable(chan, toset)​

Enable or disable a watchdog channel.

Parameters:

  • chan (number): Channel number, default 0
  • toset (boolean): true to enable, false to disable, default true

Returns: boolean

Throws: Error if chan is missing

watchdog.restart(chan)​

Feed the watchdog (restart the timer) for a specific channel.

Parameters:

  • chan (number): Channel number, default 0

Returns: boolean

Throws: Error if chan is missing

  • dxStd: Timers (setInterval) for periodic restart() calls
  • dxLogger: Log watchdog init and feed failures during debugging

8. Examples​

None.