Programming/debugging external custom nRF52840 boards using nRF52840 DK

[Radio]

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]

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

[Radio]

Hi Simonr,

Many thanks for the reply.

I have one more question to clarify. In the link I shared above, they have connected the ground in P1 with GND_DETECT in P20. As shown below.

Do I have to do this in-order to detect an external board?

Thanks a lot!

[matija66]

Hi,

I am trying to program an extrnal nrf52840 it is Minew MS88SF2, I did exactly as desribed above at least I think I did, but unfortunatly it always programs the internal NRF. I measured power supply voltage on external NRF and double cheked connections it seems OK. I am using Mbed Studio.

Do you have any suggestions what else can I try?

Thank you very much.

[filipmrazek]

Hi!

Have you solved your problem with flashing MS88SF2? 
I have exactly the same problem. I'm using nrf52840dk revision 3.0.0 and the P20 connector has different labels than connector mentioned in the first post. 

The connector has:
VDD nrf

VDD nrf

SWD SEL

SWD IO

SWD CLK

SWO

RESET

empty

VIN 3-5v

VDD nRF_HV

VDD nRF_HV'

VIO REF

empty

Does anybody know how to connect external board with nrf52840 (MS88SF2) to flash it, please?

Thank you

[Jithu_jo]

Hi, were you able to resolve this issue. Neither my nrf52dk has a GND Detect pin

[filipmrazek]

Hi, yes I solved it. The newer version (the one with nrf53 as a programmer) doesn't use common GND to detect external board is connected. They use common VDD instead. You can see my connection in the image below.

The orange wire is connected from VDD to SWD SEL (to select external board).

My problem was, that I probably used damaged development kit (the LED 5 was not blinking or shining). I tried to use another one and then it worked!

Hope it solves your problem as well.