Try increasing the stack size. 2048 is on the low side.

Now that we have bootloader_components, I think you could wrap bootloader_utility_get_selected_boot_partition for a fairly simple and clean solution. eg. (untested): project_dir/bootloader_components/bootloader_select/bootloader_select.c: #include "soc/gpio_periph.h" #include "soc/gpio_struct.h" #in...

You're better off ensuring everything your callback needs is in IRAM. Warming up the cache seems very fragile, at best.

That means ensuring pcnt_get_event_status and digitalWrite, as well as any functions they depend on, are in IRAM too. This might be tricky to alter in an Arduino environment.

CSV is very basic, you could construct it on-the-fly from memory (assuming ESPAsyncWebServer exposes the right stuff to make it possible). It could be as simple as this (pseudocode obviously): http_server.on(HTTP_GET, "/data.csv") { response.header.set("Content-Type", "text/csv"); // TODO: set Conte...

I think there is an API to register memory blocks with the heap allocator, but I can't help being curious what your use case is for dynamically grabbing a chunk of RTC memory? What do you gain vs static?

If anyone is curious, I now have a working example of this here: https://github.com/boarchuz/esp32_rtc_boot

For reference, it takes about 500us from my EXT1 pin going low to my function being called. This is less than half the time it takes to enter the typical RTC wakeup stub.

I guess it's doing its job. Everything in the RTC domain will be untouched with a SW reset so there's always the chance that some configuration or ongoing activity interferes with reinitialisation. A RTC WDT reset will clear everything for a clean slate. What do you get with this?: xtensa-esp32-elf-...

memcpy(&recData, incomingData, sizeof(incomingData));

You're taking the sizeof a pointer, so only the first 4 received bytes are being copied into your recData struct.

12 determines the voltage of the VDD_SPI domain (ie. the voltage supplied to the flash chip, 1V8 or 3V3). You can set this voltage in efuses instead, and the pin level will then be ignored so you can connect whatever you like. 2 (along with 0) determines the boot mode (ie. run the application normal...