Connecting to STM32 Nucleo boards

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The debug interface signals have to be connected manually with the J-Link (e.g. by using jumper wires).

Pins needed for SWD interface connection:

  • SWDIO / TMS
  • SWCLK / TCK
  • SWO / TDO (optional)
  • NRST (optional, see below)
  • GND
  • VTref (Usually connected to Vdd of the target)


NRST: We recommend to connect the this pin as for STM32 devices this pin allows us to connect under reset. So even if a "bad" application, which for example remaps the debug pins, is running on the target we can connect to it.

On the Nucleo boards, a separate connector (CN4) is mounted which can be used to connect the SWD interface.

 Nucleo CN4         J-Link
 Pin 2 (TCK)  <-->  Pin 9  (SWCLK / TCK)
 Pin 3 (GND)  <-->  Pin 4  (GND)
 Pin 4 (TMS)  <-->  Pin 7  (SWDIO / TMS)
 Pin 5 (NRST) <-->  Pin 15 (nRST)
 Pin 6 (SWO)  <-->  Pin 13 (SWO / TDO)
 Any Vdd Pin  <-->  Pin 1  (VTref)