Portenta H7: Debugging via JTAg or SWD?


i'm now working for a couple of weeks with the Portenta H7. Until my written code gets more complicated, i bought the breakout board and the ST-LINK/V2 to debug my code.
But i am a little confused by the wiring between the ST-Link and JTAG pins on the breakout board. I have read several times in the forum, that you talking about JTAG, but i think you mean SWD.

I have looked up the schematics of the breakout board and the schematics of the Portenta and i have come to the conclusion, that we can't use the JTAG protocol, since the JTDI pin (PA15 of the STM32H747) is used for communication with the WiFi module. Also the test reset pin nJTRST isn't connected to the JTAG connector of the breakout board. The nJTRST pin is pin D3 from the SD card connector.

So my question, if we want to debug the Portenta we always use the SWD protocol. Is that correct?

Another point i didn't understand is why you think that the schematic of the brakout board is incorrect for the JTAG connector. https://forum.arduino.cc/t/portenta-breakout-documentation-appears-to-show-wrong-jtag-pinout/703004?u=eschi
If i measure the +3V3 and GND pins, the pins on the board are at the correct position. I think that pin 1 of the JTAG connector is indicated correctly on the breakout board.

The last point is, how do you connect the ST-Link to the brakout board. Do you just solder some cables to the pins or is there a ready to use connector.

Best regards,

You can get adapters. For example:

I personally would prefer that approach over soldering.

Thanks for the hint :slight_smile:
But i don't think that the 2x5/1.27mm pitch connector will fit the 2x10 pins on the breakout board, will it?

That's the problem with the portenta! Just nothing works! Everything you touch makes problems, JTAG connector, PWM, DMA,...

And the documentation is crap!

Why do other boards work fine and the Portenta does not? As eschi said, you even don't know how to connect JTAG, because it's not documented and you can't buy a cable without DIY. That's not PRO!

I think that one should hopefully work:

[Emulator Adapter Platte Linie 20pin 2,54mm Rpm 20pin 1,27mm JTAG 20 p Drehen 20 P|Cable Winder| - AliExpress](Emulator Adapter Platte Linie 20pin 2,54mm Rpm 20pin 1,27mm JTAG 20 p Drehen 20 P|Cable Winder| - AliExpress)