Cortex-M Debug

Overview

Use this skill to debug ARM Cortex-M firmware systematically. Start by identifying the exact MCU, board state, debug probe, toolchain, and failure phase, then choose the safest inspection path before changing flash, option bytes, clocks, or startup code.

When To Use

Use this skill when:

• The target is a Cortex-M MCU, such as Cortex-M0/M0+/M3/M4/M7/M23/M33/M55/M85.
• The user mentions SWD, JTAG, J-Link, ST-Link, CMSIS-DAP, OpenOCD, pyOCD, GDB, or vendor IDE debug.
• Firmware does not boot, cannot be flashed, stops in Reset_Handler, hits HardFault, or has no UART/log output.
• The task involves vector tables, startup files, linker scripts, clocks, reset behavior, or fault registers.

Do not use this skill when: