Can't Supply MCU power usingSTLinkV2 Isol

[Bryan M]

Posted on January 12, 2018 at 20:43

I'm using an STM isolated programmer/debugger.

I'm using it in a serial wire debugger mode (SWD) and connected VDD, GND, SWDIO and SWCLK on my board but can't supply voltage from the programmer itself. The device must be turned on first. Does anyone know if I can supply my board with 3.3v?

I'm using:

Pin1 - VDD

Pin7 - SWDIO

Pin9 - SWCLK

Pin12- GND

Pin15 -nRST

I CAN program but only with external power supplied to board itself.

On the non-isolated programmer, I could jump pin 19 to 1 and get 3.3 v and program just fine through the programmer alone but using the isolated, I can't get 3.3V. I've even probed using a volt meter but can't find how to do it.

Suggestions?

[Tesla DeLorean]

Posted on January 13, 2018 at 18:01

The Pin 19 things isn't part of the standard. Segger uses it to supply 5V

Is there are reason you're using a Isolation pod? Like you need to be physically isolated from the computer side supply.

[T J]

Posted on January 14, 2018 at 22:11

I would tie the grounds together, remove the 3.3V link from the POD to your board.

power the boards separately, it should come up.

but I would also suggest you stop using the isolated programmer.

[Tesla DeLorean]

Posted on January 14, 2018 at 22:15

I think the pod needs the 3.3V to drive the target side buffers

[Zt Liu]

Posted on January 15, 2018 at 04:56

Hope that answer your question. 

By the way the Target VCC pin needs to power the target side of inner isolator chips inside st-link/opto,

perhaps some si84xx, as the CO indicated.

.Zt

[Bryan M]

Posted on January 15, 2018 at 17:08

Yes we wanted to use an isolated programmer to reduce any change of frying the programmer.

So to confirm. The isolated programmer cannot provide any kind of MCU voltage to the target? The target must already have the voltage and the target provides the voltage to the programmer?

[Bryan M]

Posted on January 15, 2018 at 17:08

So to confirm. The isolated programmer cannot provide any kind of MCU voltage to the target? The target must already have the voltage and the target provides the voltage to the programmer?

[toby2]

Posted on January 15, 2018 at 18:39

Correct.

It is also good to see you have selected pin 12 for 0V. Don't try to use just pin 4, 6 or 8 for 0V, it will not work as I discovered today.

[Bryan M]

Posted on January 15, 2018 at 19:41

Yeah I read some other threads saying that ground is only truly on pins 12 and 18. I checked with a probe continuity setting on a meter. Annoying how the documentation claims that any of the grounds would work.

Thanks for the reply!