embedded-fault-debug

# Embedded Fault Debug ## Overview Use this skill to preserve crash evidence and find the first failing instruction. The agent should read architecture-specific fault state before reset, map addresses to symbols, and separate root cause from secondary symptoms. ## When To Use Use this skill when: - Firmware hits HardFault, BusFault, UsageFault, trap, illegal instruction, default handler, watchdog reset, assert, or panic. - The board resets unexpectedly or hangs after a repeatable action. - The user has a register dump, fault log, crash PC, stack dump, watchdog event, or GDB backtrace. Do not use this skill when the target cannot yet connect or flash; use `mcu-flashing-debug` first. ## First Questions Ask for: - Architecture/chip family and toolchain. - Exact symptom and whether it is reproducible. - Register dump, backtrace, fault/trap registers, assert log, or reset reason. - ELF/MAP file that matches the running image. - Whether the target has been reset since the fault. ## Workflow 1. Preserve state. Do not reset or reflash until fault registers, PC, LR/RA, SP, and stack frame are captured. 1. Confirm image-symbol match. Ensure the ELF/MAP file matches the firmware currently running on target. 1. Identify the faulting address. Map PC, exception return address, `mepc`, stacked PC, or return address to a symbol and source line. 1. Classify the cause. Separate invalid memory access, illegal instruction, stack overflow, alignment, bus/peripheral acces...