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Some details with regard to stack limit configured in the ESP32 Arduino core.
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timemage
timemage
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Simple minimal change

So, I'm not going to tell you that this is a good idea, but a minimal change would be to static qualify this as static unsigned int number[8199]; Then you won't get that reset cause, here, for this reason.

Some details for anyone curious

If you want to see some of the guts, you look in the ESP32 core for Arduino where it creates the task that ultimately runs setup() for you. You can see that it calls getArduinoLoopTaskStackSize() returning ARDUINO_LOOP_STACK_SIZE which by default is 8192. 8192 bytes, not unsigned ints. With sizeof(unsigned int) being 4, this is very roughly in the vicinity of the 1800 unsigned ints where things started to fall apart in my testing above. Rather than chase down the configurion I just made a sketch that does Serial.println(getArduinoLoopTaskStackSize()); and yeah, it prints 8192.

getArduinoLoopTaskStackSize is a weakly defined function which would allow something to redefine in elsewhere in the program to overload the default one. So, just out of curiosity I wrote one as follows:

size_t getArduinoLoopTaskStackSize(void) {
  size_t r_size = sizeof(unsigned int [8199]); // exactly the size your array
  r_size += r_size >> 3; // add about 1/8 (or 12.5%) extra 
  return r_size;
}

It no longer crashes. Should you do this? Probably not. But, if you ever have a legitimate reason to put a 32K array on the stack on an ESP32 it may be an option. I mostly just did this to see what would happen. It's barely been tested.

So, I'm not going to tell you that this is a good idea, but a minimal change would be to static qualify this as static unsigned int number[8199]; Then you won't get that reset cause, here, for this reason.

Simple minimal change

So, I'm not going to tell you that this is a good idea, but a minimal change would be to static qualify this as static unsigned int number[8199]; Then you won't get that reset cause, here, for this reason.

Some details for anyone curious

If you want to see some of the guts, you look in the ESP32 core for Arduino where it creates the task that ultimately runs setup() for you. You can see that it calls getArduinoLoopTaskStackSize() returning ARDUINO_LOOP_STACK_SIZE which by default is 8192. 8192 bytes, not unsigned ints. With sizeof(unsigned int) being 4, this is very roughly in the vicinity of the 1800 unsigned ints where things started to fall apart in my testing above. Rather than chase down the configurion I just made a sketch that does Serial.println(getArduinoLoopTaskStackSize()); and yeah, it prints 8192.

getArduinoLoopTaskStackSize is a weakly defined function which would allow something to redefine in elsewhere in the program to overload the default one. So, just out of curiosity I wrote one as follows:

size_t getArduinoLoopTaskStackSize(void) {
  size_t r_size = sizeof(unsigned int [8199]); // exactly the size your array
  r_size += r_size >> 3; // add about 1/8 (or 12.5%) extra 
  return r_size;
}

It no longer crashes. Should you do this? Probably not. But, if you ever have a legitimate reason to put a 32K array on the stack on an ESP32 it may be an option. I mostly just did this to see what would happen. It's barely been tested.

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timemage
timemage
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  • 1
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  • 27

void setup() {
    char* temp;
    //Serial.printf("%s",hexstring);
    unsigned int number[8199]; <----- too much.

So, you're trying to put a 32796 byte object on the stack. I don't know exactly why you're seeing the manifestation that you are, but I'm not surprised.

I just took an ESP32-CAM and started playing with different sizes and found that around 1800 (unsigned ints) is where things start to go sideways, failing occasionally rather than constantly. By a 2000 count, it continually reboots with rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT) transitioning to rst:0x10 (RTCWDT_RTC_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT) and later to very roughly around 5000 it becomes rst:0x8 (TG1WDT_SYS_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)

I may fill out some details later if I look into it deeper. The ESP32 and SDK is complicated enough that there may well be a function can call that will permit a higher stack level. But this is mostly to satisfy curiosity.

Putting very large things (relative to the system size) on the stack is usually not done. I hesitate to try to tell you what exactly you should do; it wouldn't surprise me if you don't need this array at all for what you ultimately want to do, but that's a different question). So, I'll just say get it off the stack through either dynamic memory allocation (e.g. through new or malloc), possibly using a smart pointer (e.g. std::unique_ptr) to manage that since those are available on the ESP32, or perhaps just making the variable either a static local or global. Or again if possible finding out why you might not need this array.

So, I'm not going to tell you that this is a good idea, but a minimal change would be to static qualify this as static unsigned int number[8199]; Then you won't get that reset cause, here, for this reason.