ESP32 minimal crash capture

ESP-IDF already captures the ESP32 equivalent of an ARM HardFault. Use the ESP-IDF panic handler and ESP-IDF core dump support instead of replacing the low-level exception path.

The panic handler captures the architecture-specific fault frame:

Xtensa targets: PC, PS, A0..A15, SAR, EXCCAUSE, EXCVADDR, loop registers, and backtrace.
RISC-V targets: MEPC, RA, SP, MSTATUS, MCAUSE, MTVAL, MHARTID, GPRs, and backtrace.

Fatal classes include CPU exceptions, interrupt watchdog, task watchdog, cache errors, brownout, stack overflow, heap corruption, UBSAN checks, and assertions.

This example enables core dump to flash. No filesystem is involved: ESP-IDF writes directly to a raw partition table entry of type data, subtype coredump.

coredump, data, coredump,, 128K

At panic time, ESP-IDF serializes the crash state into that raw flash partition. On the next boot, the application can read it with the user-mode coredump APIs:

esp_reset_reason();
esp_core_dump_get_panic_reason(reason, sizeof(reason));
esp_core_dump_get_summary(summary);
esp_core_dump_image_get(&addr, &size);
esp_core_dump_image_erase();

This example exposes:

/api/crash: JSON metadata: reset reason, panic reason, crashed task, PC, and coredump size.
/api/crash.bin: raw ESP-IDF coredump image, suitable for offline decoding with the application ELF.

The raw coredump can include task stacks, TCBs, selected memory regions, and therefore customer-private data. Production upload must treat it as sensitive diagnostic material.

Wizard integration notes

The Wizard ESP-IDF template should keep its existing mongoose_init() / mongoose_poll() structure and register the crash endpoints as custom API handlers. The relevant ESP-IDF pieces from this tutorial are:

CONFIG_ESP_COREDUMP_ENABLE_TO_FLASH=y
CONFIG_ESP_COREDUMP_DATA_FORMAT_ELF=y
CONFIG_ESP_COREDUMP_MAX_TASKS_NUM=16
CONFIG_ESP_COREDUMP_STACK_SIZE=2048

The ESP-IDF component needs espcoredump and esp_partition.

Wizard's current 4 MB OTA partition table leaves 0x10000 bytes after SPIFFS, so a 64 KB coredump partition fits without changing the app or SPIFFS sizes. The 128 KB partition used by this tutorial requires shrinking SPIFFS or one of the app slots.

coredump, data, coredump,, 64K

The WiFi code is not materially related to crash capture. Apart from where the credentials come from, the differences are retry policy, temporary event handler lifetime, WPA2/PMF station config, and whether the password is logged. Wizard can keep its existing WiFi code for this feature.