HW-MODS: A prototype board for the STLINK-V3-MODS

Since STMicroelectronics presented it, I had been very curious to try it.

Image source: ST’s UM2502

There where all the specs for being a very usefull thing: a cheap and really small debugger intended to be integrated on every custom PCB that needs onboard debugging capabilities.

I have immediatly decided to develop my own PCB in order to get it usable also as a standalone debugger.

Top Layer Layout
Bottom Layer Layout

The key features of my design are:

  • Standard 2,54mm pin header for all the availables interfaces: UART/USART, CAN, VCP, SPI, I2C
  • Directly controllable GPIOs
  • Complete JTAG/SWD interface
  • RJ12 Tag Connect TC2030 compatible debugging interface

This is the result:


Despite what is written in the User Manual (UM2502) provided from ST, I’ve found in the CAD library and verified in my board that from Pin 22 (marked as Reserved) is it possible to get the 5V coming from the USB.
I think that they have marked it as reserved because they don’t want to take care of possible inappropriate usage of that power source.
This means that there is any protection circuit with respect to short circuit, reverse polarity or over current and you may damage your pc USB port in case of problem.

So, PLEASE, take particular care and USE IT AT YOUR OWN RISK!!!
I’m not responsible of how you’re using this device at any time.


-RJ12 female connector part #: 615006143621, from Wurth Elektronik
-Standard 2,54mm pitch pin header: 2x3pin, 1x4pin, 2x5pin, 2x6pin

Design files:

The Autodesk Eagle library for the stlink-v3-mods as well as all needed design files are available in the attachments or on this Github repo.


I hope that you find this usefull and that you enjoy it.
If you want to support my work please consider to make a donation!

For any question or anything else you can use the following form!


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2 thoughts on “HW-MODS: A prototype board for the STLINK-V3-MODS”

  1. Well done! I have been using the V3 for a while now, and it is ideal. I was already using pin1 on the 14 pin connector to power the target. I discovered that a STMPS2151 was being used between the usb5v and pin22 as you correctly advertised for 5V.

    One thing I am planning to do with your footprint is to design a carrier board with power and signal isolation to the target. This should make it truly robust.

    Can’t believe these things only cost $10 Cheers!

    • Thank you very much Thomas. I’m glad that you appreciated it.
      Nice idea to isolate power and data from it. That way you’re shure that you don’t damage it at all. Have a look at the ISOW784x series from TI. It has built-in power and data.


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