Synchronization between LTE and GPS

[kaffetorsk]

According to nordic the LTE and GPS shares a physical radio resource.

While using your library it seems that if GPS is currently awaiting fix, and I send something on a socket, the send future returns Ok() even though nothing is actually sent.

Am I doing something wrong? Is this a limitation? Shouldn't the "send" future be returned after the radio resource is free, and the data actually sent, or alternatively return an Err()

Workaround so far is to use a mutex for sync.

[diondokter]

Hi, I've not run into that so far. Can you tell me what the modem api actually returns?

My guess is that we just have to add something in the various matches like here:

nrf-modem/src/socket.rs

Lines 329 to 338 in f9d4a24

	match connect_result {
	// 0 when we have succesfully connected
	0 => Poll::Ready(Ok(())),
	// The socket was already connected
	NRF_EISCONN => Poll::Ready(Ok(())),
	// The socket is not yet connected
	NRF_EINPROGRESS | NRF_EALREADY => Poll::Pending,
	// Something else, this is likely an error
	error => Poll::Ready(Err(Error::NrfError(error))),
	}

[kaffetorsk]

Testing takes a looong time when doing it on HW. Coming back with results and examples.

Meanwhile:
The match you mention is part of connect().

My architecture involves a connected socket (dtls) kept in scope by an async task. Another async task periodically pulls GPS data using start_continuous_fix() and free() (with a timeout). I have to use continuous_fix since the 9160 sporadically gives coordinates that are way of, and need to sanity check 2 sets of coordinates.

This works until the continuous_fix runs while i send to the socket

[dragonnn]

I think I am getting similar issue for time to time. Sometimes stuff is not send over an UdpSocket and sometimes when the socket is active I am never getting a fix. 2/3 times it works fine, but the other don't and it always happens when I am not connected to it so I could get any logs yet :/.
Just right now it was running with a socket open for ~3h and didn't get a single fix (it is retiring to re run start_continuous_fix when it timeouts after 5 minutes) and it got a fix right after closing a socket because it send me an sms when it finds a fix after it lost it.

[diondokter]

Ok, good to know. I don't really have the bandwidth to look into it though.

Nordic probably has docs surrounding this issue and I think I've seen some APIs before. So there likely is a solution in some form.

[dragonnn]

Maybe this https://docs.nordicsemi.com/bundle/ncs-2.0.0/page/nrfxlib/nrf_modem/doc/api.html#c.nrf_modem_gnss_prio_mode_enable ?
But I am not aware if my SIM does support eDRX, I kind suspect not, but I will try it anyway if it helps.
But that could make the problem of LTE not sending stuff sometimes when GNSS is running even worse.

[diondokter]

I don't know, it might help!

You can try by just calling that function and seeing if that helps