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  • Case ID: 282779
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nrf9160 DK -- Side effects of external power supply P21

Sebastian Stein

Dear Nordic Support Team,

I am developing an application for the nrf9160 DK version 1.0.x (nrf connect sdk 1.8.0 and modem firmware 1.3.1). The application depends on other hardware periphery connected to the board via UART and SPI interfaces. The periphery is powered via the board (I use the 5 V pin, a VDD pin and several ground  pins). SW9 is switched to 3V. I have a power adapter which delivers 5 V (max. 2 A) via a USB plug or two pins.

So far, I test my application only while supplying the nrf9160 DK via it's USB interface (from my laptop or with the aforementioned power adapter). All tests made with this setup worked as expected. However, when I supply the nrf9160 via it's external power supply interface (P21), using the pins instead of the USB plug of my power adapter, the application does not wok anymore.

I noticed one difference on the board so far. If I supply the nrf9160 DK via its USB interface, the power between a ground pin and the 5 V pin is, as expected, approximately 5 V. However, if I supply the nrf9160 DK via P21, the power between a ground pin and the 5 V pin is close to 0 V. With this fact in mind, it does not surprise me that my application fails, since my periphery isn't supplied anymore.

I have three questions in this context:

  1. Can you please help me to understand the behavior I am seeing?
  2. What other side effects occur when not supplying the board via its USB interface?
  3. What do I have to do when I just want the board to behave the same regardless of the power supply interface in use or rather, how do I disable the side effects and get my application running while supplying the board via P21?

I attached my nrf9160dk_nrf9160_ns.overlay file to provide a little context on my hardware periphery in use.

nrf9160dk_nrf9160_ns.overlay

Thank you for your time. Please don't hesitate to ask if you have any questions.

Cheers,
Sebastian

  • 0 in reply to Håkon Alseth

    Hi Håkon,

    thank you for your answers.

    Håkon Alseth said:
    The three uart's are effectively disabled, as the segger IC is not connected physically connected over USB. In case you are using one, or more, of the uart instances with hardware flow control, then it will be stuck waiting for the host.

    I have the impression that we mean different things when we use the notion UART. I am talking about the physical / electronic UART interfaces of the chips (MCU or nrf9160 SiP). I believe that you are referring to the three virtual comports the segger IC provides, which seem to be connected to the three UARTs via the MCU. But I admit that I am getting a little ahead of myself here since I am not an electrical engineer.

    What I am seeing is, that if I supply the nrf9160 DK via P21, connect my periphery to the pins defined as tx an rx of uart3, and use zephyrs UART driver to communicate with my periphery, everything works as expected. Thus, I believe that the physical UARTs are not disabled when supplying the board via P21. This means, that everything is fine on that front.

    It turned out, that my sole problem was, that my periphery wasn't supplied anymore by the board's "5 V Pin" when supplying the board via P21. Since you explained to me, that this is the expected behavior of the nrf9160 DK, I consider this case closed.

    Thank you for the insights.

    Kind regards,
    Sebastian

  • 0 in reply to Sebastian Stein

    Hi Sebastian,

     

    I am glad to hear that you solved the issue!

    Sebastian Stein said:

    I have the impression that we mean different things when we use the notion UART. I am talking about the physical / electronic UART interfaces of the chips (MCU or nrf9160 SiP). I believe that you are referring to the three virtual comports the segger IC provides, which seem to be connected to the three UARTs via the MCU. But I admit that I am getting a little ahead of myself here since I am not an electrical engineer.

    What I am seeing is, that if I supply the nrf9160 DK via P21, connect my periphery to the pins defined as tx an rx of uart3, and use zephyrs UART driver to communicate with my periphery, everything works as expected. Thus, I believe that the physical UARTs are not disabled when supplying the board via P21. This means, that everything is fine on that front.

    It turned out, that my sole problem was, that my periphery wasn't supplied anymore by the board's "5 V Pin" when supplying the board via P21. Since you explained to me, that this is the expected behavior of the nrf9160 DK, I consider this case closed.

    I am sorry for creating confusion around this topic, that was not my intention.

    You are right, the NRF9160 UART peripherals are not disabled, but the usb-uart bridge on the debugger IC will be, so if you potentially had one uart enabled towards this usb-uart bridge with hardware-flow control enabled, your firmware would have misbehaved (never getting permission to send).

     

    I hope you have a wonderful weekend, Sebastian! Please feel free to contact us if any new issues should pop up.

     

    Cheers,

    Håkon

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