J-Link does not connect to nrf51822

[Jasper]

I want to reprogram a nRF51822 xxAC device on a existing product. I have a J-Link (SEGGER) device with latest firmware. I'm running the SEGGER J-Flash V6.20e utility. I have connected the DIO and CLK lines to the SWD lines on the J-Link I also connected the VTref pin to the VDD of the CPU. It measures 3.0V. Flash utility of the J-Link also reports it as 3.0V The CPU runs on 3.0V Is this ok for programming or must it be 3.3? I measured the DIO and DCLK lines (with a scope) and they don't go higher than 1.2V They also doesnt go anywhere else on the pcb so I'm not sure if this is correct. The PCB is running an app currently so it is definitely working. (NOTE: It might be running the CPU in low power mode or even OFF mode)

Any ideas Why the programmer does not want to Connect? ... and yes, I did connect the ground as well ...

[Bjørn Kvaale]

Which Segger J-Link device are you using? I think 3.0 V should be fine for programming, but this could depend on which J-Link device you are using. What is interesting is that the DIO & CLK are only 1.2 V. This does not seem correct. Have you taken a look at these two cases yet (case 1 & case 2)? It seems your cable connections are setup correctly, as you have connected SWDIO, SWDCLK, GND and VCC. Just double check this to make sure the J-Link is correctly connected to the nrf51. Also, check the two cases I linked to and see if any of those tips might be helpful. Kind Regards, Bjørn

[Jasper]

Eventually got the J-Link to connect to the device and program. The problem it seems was that the nRF SCLK pin was blown. It could have been when I soldered on to the pin or maybe when I measured.

I simply used another PCB and it all worked fine.