nRF51 Dk damaged

[Bimal]

Hi,

I have my custom nRF51822 board, and i used to flash the firmware through nRF51 DK kit. As there are two ports through which we can load external boards i was using P20 connector as its mating connector is easy to get. Suddenly i found that while i was working with software part and custom board and nRF51822 where connected with P20 connector. It damaged my custom board SoC(nRF51822) and MCU of nRF51 DK board.

Can you please help me out for following quires/Observations:

• Now i am seeing that P20 SWDIO and SWDCLK are shorted with Ground of nRF51 DK.
• Also 3.3V(VDD) and GND are showing me shorted, so i guess MCU has damaged.
• It also shorted my custom board 3.3V and GND, show i replaced SOC(nRF51822) and now its working fine individually.
• Please tell me is there any protection required on SWD interface.
• Is there any specific reason for this damage.

Need your feedback, As this is stoping me from further process.

[Bimal]

No, In our board we are generating 3.3Volt from 5.2V Zener diode, and which is very stable output +-<80mV.

Also i think you get it wrong, While flashing the external board it damaged the external board and the Atmel Segger chip on Development kit(nRF51-DK). Is that Atmel Segger is very sensitive to this and do we need to put any protection on custom external board in any of the pin like.

1. VCC=3.3V pin,
2. GND pin,
3. SWDIO pin,
4. SWDCLK pin

Please share your feedback for the same.