CMSIS-DAP provides a standardized way to access the Coresight Debug Access Port (DAP) of an ARM Cortex M0 M0+ M3 M4 MCU via USB. It provides direct USB connection from a development board to a debugger running on a host computer on one side, and over JTAG or SWD to the target device to access the Coresight DAP on the other. Click CMSIS-DAP to get more information.

This project is an ARM CMSIS-DAP debugger firmware porting on STM32 device. I purchased a minimal system board from taobao.com, cost me about 17 CNY(less than 3$). With this firmware and board, I can debug Cortex M series MCUs from other verdors such as GigaDevice NXP etc. For STM32, maybe ST-Link is a better choice.

For simplicity, I removed rarely used JTAG-Debug, Mass storage, Virtual COM features, kept only the SWD-Debug feature. This leads to smaller code size and gets rid of the trouble of install drivers on Windows.

The SYSCLK of STM32F103C8 is 48M and the code size about 12kB, so the minimal requirement is STM32F102C4.

First of all, Flash your STM32F103C8 development board with CMSIS-DAP firmware, then your development board becomes a CMSIS-DAP Debugger.

Connect SWCLK, SWDIO, nRESET, GND to your target board, VCC(5V/3.3V) is optional. You can power your target board with CMSIS-DAP.

Press Alt+F7, click the Debug Tab, select CMSIS-DAP Debugger, and click Settings button.

Check CMSIS-DAP parameters.

Now you can Erase Download Debug your target board.