DIY STM32 Programmer (ST-Link/V2-1)

Original ST-Link

ST-Link devices are almost essential when developing software for the STM32 MCUs. They are relatively cheap and easily available.

They roughly fall into two different categories. ST themselves make a number of them and they all work quite well.

One thing that annoys me with the original ST-Link devices is that the programming header is unlabelled. This essentially mean that every time I use it I have to Google for the actual pinout.

Also, the ones I've got (the one in the photo to the right) are ST-Link/V2 devices.

Chinese knock off ST-Link/V2

There are also a lot of Chinese clones available and while they have some limitations they also work quite well.

Unfortunately these devices are also ST-Link/V2 devices, and they do not have the SWO pin on the header, so any debug trace is impossible. For flashing and normal debugging they work fine though.

In short, the ST-Link/V2.1 devices offer a few extra features:

1. Serial Wire Trace (SWO)
2. Virtual serial port
3. Mass storage

All features that, while not absolutely essential, does come quite handy.

Another reason for creating my own "programmer" is that I can experiment with using a GigaDevice GD32F103, which are much easier to source at the moment.

Original ST-Link V2.1

The schematic of the original ST-Link is readily available

Schematics

Based on ST's original schematics, creating a version using only parts from JLCPCB's parts library was easy.

One thing I left out was the serial resistors of the programming header. This might very well come back and bite me in the ass but space is going to be at a premium.

PCB

The final rev. a layout looks like this:

The KiCAD 3D model:

Gallery rev. a w. GD32F103CB

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Miscellaneous Links

• Github Repository of schematics and pcb
• NUCLEO-XXXXRX Schematics (includes ST-Link V2.1
• BUILDING A CUSTOM ST-LINK V2.1
• Chinese blog post creating a custom ST-Link