Programming/debugging external custom nRF52840 boards using nRF52840 DK

Question

Hi All, 
 I came across this thread regarding programming external boards. ( https://devzone.nordicsemi.com/f/nordic-q-a/14058/external-programming-using-nrf52-dk ) 
 In order to program my external board using my DK, I am going to use the following setup as described in the above link. "P3 Socket" is in my external circuit. 
 
 1. Is there any other modifications need to be done to the DK if I am using the nRF52840 DK to program external circuits? 
 2. In my design, VDD_nRF in the DK is connected to the VDD_nRF in the external board. In this case should I remove external board battery as well? Can I also power up my external board this way? 
 3. If I am to debug my board using Segger Embedded Studio, can I use the above connection directly? 
 4. If I use the above connection, how does it affect the current nRF52840 chip in the DK? Should disable any connections to this chip in the DK? 
 5. The "RESET" in the DK, should I directly connect to the RESET pin in the external board? Is it necessary to have it? 
 6. Why does it named as GND_DETECT in the DK instead of just GND?

Simonr · Accepted Answer

Hi 
 1. No, the debugger on the DK will detect that an external board is detected and program the custom board instead of the onboard nRF. 
 2. When you program an external board like this, you should only power the custom board from the DK. You should remove the battery as that is not needed. 
 3. Yes, you can use this connection method to debug as well. 
 4. The debugger will not communicate with the onboard nRF on the DK when you have an external board connected like this, so the onboard chip is left to run whatever code was on it from before. It will not affect the debugger or the external board at all. 
 5. No, the RESET pin is not necessary to connect to the external board. 
 6. This is one of the ways the DK detects that an external board is connected to the pin header, and knows that the custom board should be programmed, and not the onboard chip. 
 Best regards, 
 Simon

Simonr · Answer

Hi 
 Yes, the GND_DETECT should be connected to the same GND that your custom board's GND is connected to. 
 Best regards, 
 Simon

karujoe1406 · Answer

I'll share what worked for me using the newer version of NRF52840 DK. I am powering the custom board with 1.8V, so the SW10 (VEXT &rarr; nRF) switch was switched to ON. The rest of the connection is as the image below (NRF DK) VDD NRF' + SWD SEL --------- Custom Board NRF VCC (NRF DK) SWD IO --------- Custom Board SWD IO (NRF DK) SWD CLK --------- Custom Board SWD CLK (NRF DK) External Supply GND --------- Custom Board GND

Programming/debugging external custom nRF52840 boards using nRF52840 DK

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