openslab-osu / featherfault Goto Github PK

FeatherTrace saves registers pushed onto the stack to a register dump and takes a stacktrace, printing this information on reboot. While a full stacktrace as found in FeatherTrace requires changing compiler flags, saving the pushed registers would only require an inline assembly interrupt handler similar to the one found here. As a result, integrating this feature into FeatherFault would be a useful way to get around being unable to MARK some areas of code while still allowing FeatherFault to be Arduino IDE compatible (unlike FeatherTrace). An external program and the elf from the current build (hopefully compiled with -g3?) would be required to translate the saved address into a line number, but this would be useful information if the line was not MARKed.

The implementation of this ISR would be based on the link above, and would rely on the exception handling behavior in the Cortex-M0+.

I have a board with a new bootloader from Adafruit.
VID is 0x239a
PID is 0x0015

Please update the recover_fault.py script to support the new bootloader.

Normal operation, VID is 0x800b

FeatherFault fails to compile when being used with the Adafruit SleepyDog Library. This issue is caused by both FeatherFault and SleepyDog defining WDT_Handler function, causing a multiple definition error during link time:

C:\Users\User\AppData\Local\Temp\arduino_build_638914\libraries\Adafruit_SleepyDog_Library\utility\WatchdogSAMD.cpp.o: In function `WDT_Handler':

C:\Users\User\Documents\Arduino\libraries\Adafruit_SleepyDog_Library\utility/WatchdogSAMD.cpp:167: multiple definition of `WDT_Handler'

C:\Users\User\AppData\Local\Temp\arduino_build_638914\libraries\FeatherFault\FeatherFault.cpp.o:C:\Users\zackp\OneDrive\Documents\Arduino\libraries\FeatherFault\src/FeatherFault.cpp:148: first defined here

collect2.exe: error: ld returned 1 exit status

FeatherFault needs to be able to respond to the watchdog timer, so removing WDT_Handler is out of the question. The only idea I have to resolve this issue is to implement the FeatherFault watchdog code in terms of the SleepyDog library--resulting in less-than-ideal reliability and another dependency.

For the moment I will mark this as wontfix, though I am open to other solutions.

Currently the the MARK macro takes nearly 5 milliseconds, which can add up quickly if used 20 times in a loop. I think most of this is in the string processing - extracting the filename from the FILE constant. If we move this step into the interrupt handler, we could reduce the time to copying and int and a pointer, plus the time to actually feed the watchdog. I expect this to take around 2 microseconds if the peripheral clock runs at 1MHz.

Here's my test code:

#include "FeatherFault.h"

void setup() {
  digitalWrite(13, LOW);
  delay(100);
  digitalWrite(13, HIGH);
  Serial.begin(115200);
  while(!Serial);
  FeatherFault::StartWDT(FeatherFault::WDTTimeout::WDT_8S); MARK;
  FeatherFault::PrintFault(Serial); MARK;
  Serial.flush(); MARK;
}

void loop() {
  long tic = micros();
  MARK;
  long toc = micros();
  Serial.println(toc-tic);
}

And a graph of the result