pyOCD flash (load) fails on STM32C031K4 (Custom Target)

[EmreGezer1]

Description

pyOCD is unable to flash the STM32C031K4 target via ST-Link V3. Multiple connection errors occur during the flash attempt. STM32CubeProgrammer CLI works as a workaround when using reset=HWrst and --erase all.

Note: pyOCD can read memory successfully (read32 0x08000000 returns the correct stack pointer value), so the issue is specific to the flash/erase operation.

Environment

• Target: STM32C031K4 (ARM Cortex-M0+), registered as a custom target
• Debug Probe: ST-Link V3 (STLINK-V3MODS, FW: V3J17M10B6S1)
• pyOCD version: installed in .venv
• STM32CubeProgrammer version: v2.22.0
• Host OS: Windows 10
• Connection: SWD (SWDCLK, SWDIO, VCC, GND)

Steps to Reproduce

1. Register the custom target as described in the pyOCD documentation
2. Run the following command:

.venv\Scripts\python.exe -m pyocd load --target stm32c031k4 --format elf --erase chip --connect under-reset <your_elf_path>

Observed Errors

0002829 E Error probing AP#2: STLink error (22): DP error [discovery]
0002837 E Error probing AP#3: Memory transfer fault (STLink error (17): AP fault) [discovery]
0002842 E Error probing AP#4: Memory transfer fault (STLink error (21): DP fault) [discovery]
0002846 E Error reading AP#1 IDR: Invalid AP address (#1) [discovery]
0002855 C No cores were discovered! [__main__]

Workaround

Flashing via STM32CubeProgrammer CLI works reliably:

STM32_Programmer_CLI --connect port=SWD reset=HWrst --erase all --download <your_elf_path> --verify --go

Memory Read Works

pyOCD can successfully read memory from the target, confirming the custom target registration and SWD connection are correct:

.venv\Scripts\python.exe -m pyocd cmd --target stm32c031k4 --connect under-reset --command "read32 0x08000000"
# output: 08000000:  20001800

The value 20001800 is the initial stack pointer, which is the expected value at address 0x08000000.

target_STM32C031k4.py