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nRF9160 DK as a Debugger for a second nRF9160 DK


I plan to design my own hardware based around nRF9160. Prior to this, I want to verify that I can use the nRF9160DK as a debugger for my own board. As an initial test, I plan to use two nRF9160 DK boards, one as a target and one as a debugger. I would like to verify the set up for this please.

On the "debugger" nrf9160DK, I connect a USB cable into J4.

I connected a 10pin cable from P22 (Debug Out) on the debugger board into P3 (nrf91 Debug in) on the target board. 

On the target board, I select "nRF only" via SW1.

Connect a second USB cable to J4 on the target board. This will provide power and VCOM on the target board.

So, I have three questions. 

1. Are my connections above correct?

2. Are there any other switches or settings I need to adjust

3. With only the target board connected to the PC, and SW1, nRF ONLY selected, I don't see any serial data over the USB connector.  I know my code is running, as it toggles a GPIO pin which I can monitor. Where is the serial port visible when the target is in nrf only mode? 



  • Hi Rod. 

    I believe this should work. 

    Your connections looks to be correct. Could you also set the "VDD IO" to "3V" as shown in the picture below and see if that helps: 

    Joakim Jakobsen

  • Hi Joakim,

    I have now received my second board and have configured them as detailed above. This now allows me to program my target nRF9160DK from my debugger nRF9160 which is great.

    I still am having problems seeing my serial output from the target board. When I have "nRF Only" switched to off on the target board, I see 3 possible serial terminals

    Watts-MacBook-Pro:~ Watt$ ls /dev/cu*

    /dev/cu.Bluetooth-Incoming-Port /dev/cu.usbmodem0009600405783

    /dev/cu.usbmodem0009600405781 /dev/cu.usbmodem0009600405785

    I can then see the serial output via the command

    Watts-MacBook-Pro:~ Watt$ screen /dev/cu.usbmodem0009600405781 115200 -L

    However, when I switch it to "nRF Only", all I see is

    Watts-MacBook-Pro:~ Watt$ ls /dev/cu*


    So my question is, where can I see the serial output on my target board when I switch it to "nRF Only"?


  • Hi Joakim,

    I have had another look at this. I imagine the reason I am not seeing the terminal out put is due to the way the VCOM is being routed. As a quick and easy test, I tried to connect up directly to the UART port using a UART - USB adapter.

    Looking at the overlay file in the secure_boot application, I note that TXD and RXD are connected to pins 18 & 17.

    /* needed to get the NRF_UARTE2 defined */
    &uart2 {
    	current-speed = <1000000>;
    	status = "ok";
    	tx-pin = <18>;
    	rx-pin = <17>;
    	rts-pin = <19>;
    	cts-pin = <21>;
    &spi3 {
    	status = "ok";
    	sck-pin = <10>;
    	mosi-pin = <11>;
    	miso-pin = <12>;
    	ss-pin = <13>;
    	spi-max-frequency = <4000000>;

    Unfortunately, this did not work.

    Any thoughts as to why I am not seeing thermal output when I switch the board to nRF Only mode?



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