XDS100V3 doesn`t connect to TMS320F28069M Through Optoisolator

[stoyanoff]

Greetings! I`ve just got your XDS100V3 and I was able to connect directly to the microcontroller. Everything seems to work properly. But I want to use an opto isolation between the controller and the programmer, because it is a high voltage/high power device. So I have an optoisolator based on ISO7240 and ISO7231 which works with XDS110. But with your debug probe i have an error SC_ERR_PATH_BROKEN. I don`t have anything connected on the probe side - no pull ups or downs. Only Vtref, GPIOOUT1 and GPIOOUT2 have 10k pull up resistors. As I said it works with XDS110 and it is taken by a TI design. What should I do to fix it?
Thanks!

[LubOlimex]

Probably XDS110 can power the isolation adapter and I am not sure if the XDS100v3 can power your isolation adapter.

[stoyanoff]

I have a separate power supply and I am not using the XDS as a powersource.
Do you want a schematic?

[LubOlimex]

Sure I will take a look. Still not sure if you have another extra power supply your insulator would do the job, or maybe you have two insulators - one for the power supply and another between the XDS and the target?

[stoyanoff]

So here is my schematic  Цък
the schematic is based on LAUNCHXL-F28069M. Previously I used modification of the controller with 100 pins package. Now I am using 80pins package. And I`ve noticed that the connection with my XDS110 through the optoisolator is unstable. My suggestion is that i`m missing some pull up/down resistors on SDI,TMS or SCK pin on the controller side.
Any suggestions?
Thanks!

[LubOlimex]

Maybe the opto-couplers are just too slow - are you using the slow or the fast version of optocouplers? 25Mbps or 150Mbps ones?

Did you try to reduce the connection frequency, maybe it will work better at lower speed?

Also we have a board with C2000 chip, maybe compare the JTAG lines with our design:

https://www.olimex.com/Products/DSP/Development/TMS320-P28016/

and schematic is here:

https://www.olimex.com/Products/DSP/Development/TMS320-P28016/resources/TMS320-P28016-REV-A-sch.gif

[stoyanoff]

Interesting! You have pull ups on TMS, SCK and TDI. And a small pull down group on SCK. I can add them to my schematic and check.
By the way, this is the second time which i hear about these 150Mhz versions of the digital isolators. I only find 25Mbps versions, but I think it should be enough because I tried to decrease the speed to 1Mhz with no success.
So I will add the neccessary pulls and will write again!
Thanks!

[stoyanoff]

No effect! I`ll change the approch. I will try to build an optoisolator based on Toshiba TLP2767.