Why debug prints over ITM do not work with ST-LINK/V2 ISOL?

[Pavel A.]

Posted on March 04, 2018 at 15:02

I have STM32F446 with external ST-LINK/V2 white plastic dongle.

Debug prints via ITM trace work fine with Keil uVision and ST-Link utility.

Today I got an isolating dongle ST-LINK/V2 ISOL.  Everything seems to work with it except of debug prints.

This does not look a Keil issue because ST-Link utility does not show prints either.

Are any changes in debug settings needed for ISOL?

Can anybody confirm that ITM debug prints work with ISOL?

I've connected the same target cable to the ISOL that I use with normal ST-LINK

(entire cable chain with connectors, from the dongle to the board).

The ISOL is original new item ordered directly from ST, in a nice box etc.

Thanks,

 -- pa

#st-link/v2-isol-programmer/debug

[Tesla DeLorean]

Posted on March 04, 2018 at 15:04

The SWO pin (PB3/JTDO) needs to feed over the isolator.

[Pavel A.]

Posted on March 04, 2018 at 16:41

Clive,

All the pins/wires go into the dongle (either ISOL or normal)... do you mean to reconnect SWO inside the dongle?

-- pa

[Tesla DeLorean]

Posted on March 04, 2018 at 17:15

So basically a Tag-Connect type system

https://www.segger.com/products/debug-probes/j-link/accessories/adapters/6-pin-needle-adapter/

 

Ok, so SWO is there.

I'm saying that SWO/JTDO needs to cross the isolation boundary for the SWV functionality to work properly. More generally the core clock needs to agree at both ends. Perhaps there is a bandwidth limit here? You'd need to probe/review the circuit inside the ST-LINK/V2 ISOL pod, but I'd assume it would need JTDO to support JTAG operation.

Segger's isolator bridges SWO

https://www.segger.com/products/debug-probes/j-link/accessories/isolators/j-link-swd-isolator/

 

[Pavel A.]

Posted on March 04, 2018 at 19:02

Er.. this is complicated. It works with a normal ST-LINK V2.

Anyone from ST, please, confirm that ISOL is drop-in replacement for a normal ST-LINK/V2?

If not, does it support ITM trace & debug prints with Segger 6-pin needle adapter?

--pa

[Pavel A.]

Posted on March 05, 2018 at 01:12

The problem disappeared by itself after few resets, power cycles, shuffling ST-LINKs around and other 'ritual dances'.

Debug prints thru ITM are unfortunately bristle and can stop working even when other debugging functions and download work

:(

-- pa