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nRF9160 LTE modem coexistence interface

I'm trying to understand how to make use of the nRF9160 LTE modem coexistence interface in a design.  I started asking about this topic in another thread about the BLE Gateway sample app: https://devzone.nordicsemi.com/f/nordic-q-a/46778/lte-sensor-gateway-sample-app

I've seen the spec entry for the LTE modem coexistence interface here: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf9160%2Fdita%2Fchapters%2Fradio_lte%2Fgnss_coext_if.html

However, I'm looking for more information.  Is there any further documentation of this interface?  In general, how is this interface intended to be used in a design?  Can you describe its use?  Can you give an example?

Without knowing more, I do still have some other questions:

Are these pins already handled in modem firmware or elsewhere in the SDK, or do they need to be supported by application code written by your users?  Is there source code that I can look at to help understand how the interface is used?

If already supported by code:

How is the interface enabled/disabled?

With COEX0, does a high input inhibit transmit by the LTE modem?

How is COEX1 intended to be used?  I don't understand what is meant by "Active high time mark pulse, which is synchronous to LTE system time.".

Thank you,

Erik

Parents
  • Hi Erik,

    For the nRF91 DK:

    The number of GPIO pins we have chosen between the nRF9160 and the nRF52840 on the DK is to give users flexibility in choice of IF, i.e. UART, SPI, 2wire with some extra interrupt ins. if needed.
    That means the user doesn't have to use 6 GPIOs, a simple UART IF would for example only need 2 GPIOs.

    When it comes to the coexistence interface this is mapped out to be up to 3 pins, aligning with what many other have in their coexistence interface.

    (However, at the moment we are only using one of the pins, basically a signal that goes active when the modem in nRF9160 goes active)

    The functionality of the COEX pins are handled by the modem firmware.

    • So for your design you currently need 1 COEX, but you should route 2-3 for future proofing.

    So basically you may choose to use only one pin in the coex interface, and for the data interaction you can use any of pins on both nRF91 and nRF52.

    Best Regards,

    Martin L.

Reply
  • Hi Erik,

    For the nRF91 DK:

    The number of GPIO pins we have chosen between the nRF9160 and the nRF52840 on the DK is to give users flexibility in choice of IF, i.e. UART, SPI, 2wire with some extra interrupt ins. if needed.
    That means the user doesn't have to use 6 GPIOs, a simple UART IF would for example only need 2 GPIOs.

    When it comes to the coexistence interface this is mapped out to be up to 3 pins, aligning with what many other have in their coexistence interface.

    (However, at the moment we are only using one of the pins, basically a signal that goes active when the modem in nRF9160 goes active)

    The functionality of the COEX pins are handled by the modem firmware.

    • So for your design you currently need 1 COEX, but you should route 2-3 for future proofing.

    So basically you may choose to use only one pin in the coex interface, and for the data interaction you can use any of pins on both nRF91 and nRF52.

    Best Regards,

    Martin L.

Children
  • So you have implemented COEX2, it sounds like.  Without COEX0, how does one ensure that the modem won't transmit while the BLE MCU is transmitting?

    Can you point me to an explanation of how the other pins might work?  You said it aligns to what many others have for LTE coex interfaces.

    Is there a "typical" or recommended encoding to use for data sent over the UART, from the external MCU, to be transmitted by the nRF9160?  A convenient approach, or is it best to tailor that to the particular data needing to be sent by the modem?

    Thanks

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