The processor was restarted by its watchdog

What ArduPilot says:

• Forcing logging for watchdog reset
• Internal errors 0x800 (watchdog_reset)

A hardware timer, the watchdog (BRD_OPTIONS bit 0, on by default), restarts the processor when the main loop stops running. Starting after such a restart, ArduPilot records watchdog_reset, sends a “WDG: …” line that says where the code was, and, if it was armed at that moment, turns logging on at once (“Forcing logging for watchdog reset”). Copter starts disarmed again: in flight that means the motors stop.

What to do, most likely first

1. The firmware locked up or crashed: a bug, most often in a beta or custom build, a new driver or a script.

   CheckCopy the whole “WDG:” line; with a crash there is also “CrashDump data detected”. What was changed before the first restart?

   FixDo not fly. Flash the stable release for your board, remove new scripts, and report the “WDG:” line with a log to the ArduPilot developers.

2. A device, or the code that talks to it, holds the main loop up.

   CheckThe IE number in the “WDG:” line is the internal-error mask of the run before the restart: main_loop_stk, spi_fail or i2c_isr there point at a device. Unplug what you added last.

   FixReplace the device or its cable, and test on the bench for as long as a flight lasts before flying again.

A dip in the power supply is not this: after a power loss the board starts as from switch-on, with no watchdog_reset. A normal reboot clears it.

Parameters to look at

Where to do it:Setup & Tuning GuideSetup & Tuning Guide