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01. What is ST LINK

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ztakis edited this page Jul 5, 2026 · 1 revision

What Is ST-LINK?

ST-LINK is a USB debug/programming adapter used to talk to microcontrollers over SWD.

x3utils uses ST-LINK through OpenOCD to read and write flash memory on supported X3 / third-generation scooter controllers, mainly the VCU and, in some cases, the scooter Motor Control Unit.

What It Does Here

With the correct wiring and connection mode, ST-LINK can:

  • connect to the VCU or Motor Control Unit;
  • read the full 128 KB flash memory;
  • write a selected 128 KB firmware .bin;
  • verify that the written data matches the file;
  • reset or halt the CPU when the adapter supports it.

In this wiki, MCU means scooter Motor Control Unit. For the processor on a board, this wiki uses chip, CPU, or microcontroller.

What It Is Not

ST-LINK is not a normal USB cable and it is not a scooter app.

It talks directly to the VCU or Motor Control Unit. Bad wiring, unstable contact, wrong power, or flashing the wrong file can leave the VCU or Motor Control Unit unusable until recovered.

The Pins Users Usually Meet

  • SWDIO - data line
  • SWCLK - clock line
  • GND - ground reference
  • 3.3V / VTref - target voltage reference or power, depending on the setup
  • RST / NRST - reset line, used by genuine ST-LINK modes

The exact scooter-side connection points belong in the model guides.

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