Error codes and software reset codes
The M122 gcode will produce a report which contains a report with a lot of information. Included in this is the current error code and the last software reset code.
The error status in the M122 report should look something like this:
Error status: 0
The status is a bit map with the following meaning for each bit:
0x01 Watchdog turned heater off temporarily 0x02 One or more step errors occurred 0x04 Output buffer starvation 0x08 Output stack overflow 0x10 An SD card operation timed out
The full reset status included in the M122 report should look something like this:
Last reset 00:00:22 ago, cause: power up Last software reset code & available RAM: 0x0003, 1580
The last reset cause is the important bit.
The software reset code only applies to the last reset commanded by software. It is a bitmap with the following fields in the high-order bits:
user = 0, // M999 command erase = 0x10 // M999 PERASE NMI = 0x20, hardFault = 0x30, memManage = 0x40, busFault = 0x50, usageFault = 0x60, otherFault = 0x70, inAuxOutput = 0x0800, // this bit is or'ed in if we were in aux output at the time stuckInSpin = 0x1000, // we got stuck in a Spin() function for too long inLwipSpin = 0x2000, // we got stuck in a call to LWIP for too long inUsbOutput = 0x4000 // this bit is or'ed in if we were in USB output at the time
The low order bits say which module was active at the time:
modulePlatform = 0, moduleNetwork = 1, moduleWebserver = 2, moduleGcodes = 3, moduleMove = 4, moduleHeat = 5, moduleDda = 6, moduleRoland = 7, modulePrintMonitor = 8, moduleStorage = 9,
So for example 0x0003 means that the last software reset was commanded by the user (i.e. M999 command, probably generated by Duet Web Control when you did an emergency stop or you edited and saved config.g).