Custom board programs using JTAG once

dlozanov · ‎2026-06-01

Hello,

I am using an STLINK-V3SET to program a custom board that I made using STM32G431. On a bare MCU, just soldered I can connect using JTAG and program, but afterwards JTAG becomes disabled and only SWD works.

I reduced the code to only have 2 LED and JTAG enabled in CubeMX, but the issue persists.

Full chip erase does not solve the issue.

Does anyone have any idea?

Andrew Neil · ‎2026-06-01

Welcome to the forum

Please see How to write your question to maximize your chances to find a solution for best results.

In particular, for a custom board, you need to show your schematic.

Has your custom board ever worked?

Can you reproduce this on an ST board?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.