Hi There,
I am afraid I already know the answer, but I figured I would see if there is a way out. I am using the NRF52833 integrated into the BL653u module from Laird, and in layout I shorted the SWCLK line to the NFC1 pin, to avoid having to move to a higher spec of PCB fab (see image). However I am unable to connect to the module over SWD, and I'm 90% certain that the problem is due to this. For reference this is a gen2 board and relatively little changed seem Gen 1 (besides moving to the lower PCB spec and thus this change).
Ideally there would be some special programmer that I can buy that will push me through this problem, but I'm guessing I'll need to make a hardware modification or respond the boards. Any advice would be much appreciated though!
I am currently using a a J-link Plus Compact programmer, with SWD and a tag-connect programming header. I have tried setting the speed to auto at to the default of 4,000 KHz. I haven't yet wired up the SWCLK line but I will do that shortly
Edit : I took a scope trace of SWDIO and SWCLK lines during a connect operation and comparing it to a good operation the only difference is that SWCLK is getting clipped to 1.9V on these new bad boards, indicating that the tying of these pins together is indeed the issue. Is there any way to set the NRF52833 up so that it can be programmed from a lower logic level on the SWDCLK line? Or is there a clever way to buffer the SWCLK signal so that it overpowers the NFC1 pin and gets to the correct logic level?
