Segger Debug Out on DK can't see my target

[Bret Foreman]

I just got a new target board back from fab/assembly and I'm trying to use the debug out connector on the PCA10028 to program the new target.

My target is the NRF51822-CFAC-R

I've wired J19 on the DK as follows:

Pin 1 - tied to the same 3V supply that powers the DK and my target
Pin 2 - SWDIO (pin H2) on my target
Pin 3 - GND on my target
Pin 4 - SWDCLK (pin C8) on my target

In nRFgo Studio, I'm able to see the Segger on the DK but the Segger is not able to see my target device. Is there any additional setup I need to do on the DK in order to download to my device?

[RK]

The debugger on the DK needs 3.3V to work (it's in the manual), you say you're using 3.0V, so I'd start by increasing that to at least 3.3V to see if it starts working.

[MartinBL]

Where does it say that it needs 3.3V? In the nRF51 DK user guide pp. 20 it says that "The voltage supported by external debugging/programmins is 3.0V". There is actually nothing on the nRF51 DK that runs on 3.3V (by default anyway). The USB power gets regulated down to 3.3V, but the current is running through a reverse voltage protection diode with a ~0.3V voltage drop so the actual VIO (supplying the Segger chip) and VDD_nRF are usually at ~3.0V or even lower.

So I suspect the problem lies elsewhere. It should be plug and play. Do you have other debuggers to test if the problem is with your custom board or your nRF51 DK? Are you able to program other boards/kits with your nRF51 DK? Do you know for sure that your custom board is working? No shorts? All traces are connected? Do you mind posting your layout?

[RK]

I got 3.3V from, devzone.nordicsemi.com/.../ and devzone.nordicsemi.com/.../

[MartinBL]

Hm... That's unfortunate. In the first link Asbjørn is actually referring to the same user guide as I did and it clearly states 3.0V. In the second link Asbjørn says "or close to", but I agree that "close to" is pretty ambiguous. Anyway I did a test with two nRF51 DKs, one acted as the debugger and the other one as the external board powered by the first one (as OP describes). The voltage on both boards were 2.88V and it worked just fine.

[Bret Foreman]

I broke out a second nRF51 DK and connected a cable from P19/Debug Out to P18/Debug In. I did not connect the second DK to USB. Rather, I powered the second DK from a benchtop supply. Just to make sure of which nRF51 I was programming, I used the "blinky" example. I was able to see the second DK's nRF51 from the Segger on the first DK and verified that I was programming the second DK when the blinky lights on the second DK flashed as expected. So my Debug Out is working with an external target.

I then connected my new board in the same way and gave it another try, powering it from 3.3V just be be sure. No action - the Segger can't see my target.

That said, my target is extremely small and I connect to it with a custom-made programming fixture with pogo pins. There's a chance that fixture is mis-wired or the pogos are not making contact. I'm going to verify all the wiring and try to verify the pogo contacts. If all that checks out, then I'll upload the gerbers for examination by the group.