Unable to use External J-link debugger with nRF52840-DK

[Jagbir]

I'm having trouble using an external j-link probe (J-Link plus compact) with the nRF52840-DK with Segger Embedded Studio. I am powering the DK from USB (Sw9 VDD) ,using the 10 pin P18 connector on the DK to connect to the J-link plus(20 pin).When I try to "Connect J-Link" in SES it pops with an error saying: "Failed to connect to target. No idcode detected. Please check connection and Target Interface Type". Here is my pin out.

P18_DK         J-link plus side

Pin1    ßà   Pin19(VDD)

Pin2    ßà   Pin7 (SWDIO)

Pin4    ßà   Pin9 (SWDCLK)

Pin6    ßà   Pin13(SWO)

Pin10  ßà   Pin15 (RESET)

Pin3,5,9 ßà   (GND)

I have tried cutting SB60 and shorting SB59 but it did not fix my problem. The on board J-link works fine.

Thanks!

[Jagbir]

It was the custom cable which was the source of the problem. This morning  I received a 20 pin to 10 pin JTAG adaptor with a cable with which I was able to program the DK through J2 USB (SES asks me which J-link to connect) or J3 USB independently or both USB plugged together. I have always used SW9 in VDD position because when SW9 is in USB position there is insufficient current to drive the LEDs. The SW6 position is irrelevant for programing purposes but we need to toggle to default position to see the LEDs or rest of the circuit power.  

[Simonr]

Glad you were able to figure it out!

Best regards,

Simon