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4-wire JTAG interface not working on STM32F7.

GW1
Associate

Hi all,

I just got new hardware. As we needed one more pin on our processor, and we always left the JTAG-Reset Pin floating on our last designs, I switched from 5-wire JTAG to 4-wire, which leaves the JTAG-Rest Pin free. Now, I set up my SW environment and wanted to start a simple "Hello World" program on my new board. Unfortunately I get the following:

But when I switch the connection from JTAG to SWD, the connection can be established.

Am I doing something wrong? Is there a hidden button, or something else I overlook?

Kind regards,

Georg

3 REPLIES 3

Isn't your program changing the JTAG pins settings in GPIO? Using the SWD connection, read out and check the relevant GPIO pins. Or try to connect through JTAG while manually holding the chip in reset.

JW

Uwe Bonnes
Principal II

Many STM32 have the errata that JTAG only work in 5 pin mode. However I don't find this mentioned in the F7 erratas. B.t.w. why not use SWD?

GW1
Associate

Hi,

first of all, I want to thank you for your answers. Just last week, we got another new hardware with the F777 on it, per default using the 5 wire JTAG. But we cannot connect to this processor either. SWD works fine on this board too.

So I tihnk, we go on, using SWD, and will check the errata regularly.

Kind regards,

Georg