Unable to connect with JTag

[Robert]

Hi, I'm working on custom PCB and I have small issue. After making PCB I was trying to connect, but no luck - "(unable to connect to the target)"

Maybe there is something wrong with my schema:

or maybe with PCB:

I have tested with different NRF chip, and also with different crystal.

What should I test ? How to verify that chip is working ?

[awneil]

The nRF51 doesn't support JTAG - just SWD.

Do you have your debugger/programmer correctly configured ... ?

[Robert]

Yes I have ST-Link Debugger connected through SWD. I have tested with other module and it does work properly. So programmer probably is not an issue it this case.

[Robert]

The chip that I'm using is NRF51822 QFAAGO. I tested with working module by replacing chip (3 different) and it does not work there also. When I solder back the oryginal one it does work so I'm not sure what is going on.

Any idea ?

[Øyvind Karlsen]

Hi Robert,

There are several errors with your PCB. The RF part will likely not work at all. Please consult the general PCB design guidelines. And make sure that you follow the reference layout for your balun.

The major error in your design is the long tracks from the nRF51 chip to the balun, these will shift the phase of each line, and the balun will not work as intended. The length of the lines are also not equal so the differential signal will be out of phase.

Additionally it seems that you suffer from size constraints on your board, you might want to consider using the WLCSP package option instead, which has a much smaller footprint.

We provide full reference circuitry with all necessary Altium files, these are available in CSP and QFN packet variants.

If you are having trouble seeing how to connect programming pins or other, you can see how it is handled in the design files for the development kit or dongle.

Hopefully this answers your questions. Best regards,

Øyvind

[Robert]

Hei Øyvind, Thank you for your answer. I'm newbe in this subject so I will redesign PCB based on your comment and also on guidelines. I'm going to Oslo later today so I will have time there to teach myself more in this subject :)

Unfortunately is does not answer to my problem which was about connection through SWD - and this part does not work at all. I ttried to replace NRF51 chip on working module with the one (or three) that I have but non of them seems to work so I have to order different version.

Does this design looks more proper ?

Thank you, Robert