External Programming with nRF5-DK P20

[DanKA]

Hello everyone,

i know that there are many similiar questions on the DevZone but i am not able to get it work and i dont uderstand it yet. I want to flash a custom board.

I connect the nRF5-DK to the custom board as the following:

• Custom Board powered with 3V coin cell
• P20 Pin 2 VDD to VDD of custom board
• P20 Pin 4 SWDIO to SWDIO of custom board
• P20 Pin 5 SWD CLK to SWD CLK of custom board
• P20 Pin 8 GND DETECT to GND of custom board. Also tried to use GND of P13  or both. As shown in other questions.

When i use nRFgo Studio , always the internal nRF is flashed. I know the priority is as follows:

• If target power (3V3) is detected on P19 (= some board is attached and powered) it uses that as target, nothing is sent to P20 or internal nRF52 chip.
• If nothing detected on P19 but target power is visible on P20 then it targets this interface (not the internal nRF52 chip).
• If P19 and P20 seems to be unpowered then SEGGER J-Link OB target's built-in nRF52 chip on the board

I applied 3,0 to 3,3 V to P20.2 and P20.8 (just the voltage, no custom coard) and still the internal chip was succesfully flashed. In that case expected something like a failure. What would you expect here?

On Software side i start with the blank blinky from the sdk. I modified pca10040.h to be suitable with my custom board. One LED is common for both (nRF-DK and custom) so that i know which chip was used.

Do you have any suggestions or guaidance? I want to use P20 as i do not have the connectors for P19 yet.

Edit: I did the test with the external voltage because i would like to indicate, if my custom board has a failure. (Eg Board is powered up, but faulty --> error while flashing)

Kind regards

DanKa

[Håkon Alseth]

Hi,

 

You'll need to apply voltage to the "VTG" pin on header P20 (pin 3).

You can do this by shorting P20, pin 2 and 3, as this will force the segger IC to externally program on P20.

 

You can then power your external board from "VDD_NRF" (P20, pin 1), just remember to remove the battery first.

 

Could you try this and see if you have any luck?

 

Best regards,

Håkon