Assert COEX0 without internal GPS on

[dsmith115]

Hello, we have a device that uses the nRF9160 with an external GPS receiver that is controlled over I2C.  I have connected the LNA enable pin to COEX0 on the nRF9160, but it seems I should have examined the documentation more closely for this pin.

Per this doc: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fref_at_commands%2FREF%2Fat_commands%2Fsip_pin_configuration%2Fsip_pin_configuration.html

It seems the COEX0 pin will only be asserted high when the internal GPS is enabled.

I have tried sending the AT command "AT%XCOEX0=1,1,1570,1580" and also set this:

CONFIG_NRF9160_GPS_SET_COEX0=y

but it still does not work.

Is there a way to set COEX0 high without the internal GPS being enabled?

Using modem firmware mfw_nrf9160_1.3.1 on rev 2 silicon, NCS v1.7.0.

[Didrik Rokhaug]

Hi,

The COEX0 pin is controlled by the modem, which doesn't know what the external GPS module is doing.

Instead of the COEX0 pin, you can use one controlled by the application, or if available, one controlled by the external GPS module.

Best regards,

Didrik

[dsmith115]

Hi Didrik, unfortunately I already have a custom board with the COEX0 pin connected to the external LNA. I am trying to determine if there is a software solution to assert the COEX0 pin without turning on the nRF9160 GPS.

[Didrik Rokhaug]

No, there is no way for the application to control the COEX0 pin directly.

And the modem doesn't know about the external GPS module, so it cannot set the COEX0 pin when the external GPS is running.

The only plausible solution I can think of, would be if you can configure the COEX0 pin to be high when you are not using LTE, and only run the GPS when you are not using LTE. But, I haven't checked if this is possible, and it would also mean that the LNA is left on when both the GPS and LTE is sleeping, which will consume extra power.