Why is the GPS operation always blocked

[duxinglang]

One of my projects needs to use NB and GPS functions at the same time. When testing, I found that even though NB network is not transmitting data, after I start GPS, I often receive messages that the operation is blocked. Why is that?  

This is my code:

static void set_gps_enable(const bool enable)
{
	u8_t tmpbuf[128] = {0};
	
	if(enable == gps_control_is_enabled())
	{
		return;
	}

	if(enable)
	{
		at_cmd_write("AT+CFUN?", tmpbuf, sizeof(tmpbuf), NULL);
		LOG_INF("modem status:%s", tmpbuf);
		if(strcmp(tmpbuf, "+CFUN: 1") != 0)
		{
			if(at_cmd_write("AT+CFUN=1", NULL, 0, NULL) != 0)
			{
				LOG_INF("Can't turn on modem!");
				EnterIdleScreen();
				return;
			}
		}
		
		LOG_INF("Starting GPS");
		gps_control_start(K_NO_WAIT);
		gps_is_on = true;
		gps_start_time = k_uptime_get();
	}
	else
	{
		LOG_INF("Stopping GPS");
		gps_control_stop(K_NO_WAIT);
		gps_is_on = false;
		gps_fix_time = 0;
		gps_local_time = 0;
	}
}

static void gps_handler(struct device *dev, struct gps_event *evt)
{
	u8_t tmpbuf[128] = {0};
	
	switch (evt->type)
	{
	case GPS_EVT_SEARCH_STARTED:
		LOG_INF("GPS_EVT_SEARCH_STARTED\n");
		gps_control_set_active(true);
		break;
		
	case GPS_EVT_SEARCH_STOPPED:
		LOG_INF("GPS_EVT_SEARCH_STOPPED\n");
		gps_control_set_active(false);
		break;
		
	case GPS_EVT_SEARCH_TIMEOUT:
		LOG_INF("GPS_EVT_SEARCH_TIMEOUT\n");
		gps_control_set_active(false);
		break;
		
	case GPS_EVT_PVT:
		/* Don't spam logs */
		LOG_INF("GPS_EVT_PVT");
		
		if(test_gps_flag)
		{
			u8_t i,tracked;
			u8_t strbuf[256] = {0};

			memset(gps_test_info, 0x00, sizeof(gps_test_info));
			
			for(i=0;i<GPS_PVT_MAX_SV_COUNT;i++)
			{
				u8_t buf[128] = {0};
				
				if((evt->pvt.sv[i].sv > 0) && (evt->pvt.sv[i].sv < 32))
				{
					tracked++;
			
					sprintf(buf, "%02d|%02d;", evt->pvt.sv[i].sv, evt->pvt.sv[i].cn0/10);
					strcat(strbuf, buf);
				}
			}

			sprintf(gps_test_info, "%d,", tracked);
			strcat(gps_test_info, strbuf);
			gps_test_update_flag = true;
			
			//LOG_INF("%s\n",gps_test_info);
			//UpdataTestGPSInfo();
			//TestGPSShowInfor();
		}
		else
		{
			sprintf(tmpbuf, "Longitude:%f, Latitude:%f, Altitude:%f, Speed:%f, Heading:%f", 
								evt->pvt.longitude, 
								evt->pvt.latitude,
								evt->pvt.altitude,
								evt->pvt.speed,
								evt->pvt.heading);
			LOG_INF("%s",tmpbuf);
			
			LOG_INF("Date:       %02u-%02u-%02u", evt->pvt.datetime.year,
						       					  evt->pvt.datetime.month,
						       					  evt->pvt.datetime.day);
			LOG_INF("Time (UTC): %02u:%02u:%02u\n", evt->pvt.datetime.hour,
						       					  evt->pvt.datetime.minute,
						      					  evt->pvt.datetime.seconds);
		}
		break;
	
	case GPS_EVT_PVT_FIX:
		LOG_INF("GPS_EVT_PVT_FIX");

		if(test_gps_flag)
		{
			u8_t i,tracked;
			u8_t strbuf[256] = {0};

			memset(gps_test_info, 0x00, sizeof(gps_test_info));
			
			for(i=0;i<GPS_PVT_MAX_SV_COUNT;i++)
			{
				u8_t buf[256] = {0};
				
				if((evt->pvt.sv[i].sv > 0) && (evt->pvt.sv[i].sv < 32))
				{
					tracked++;
			
					sprintf(buf, "%02d|%02d;", evt->pvt.sv[i].sv, evt->pvt.sv[i].cn0/10);
					strcat(strbuf, buf);
				}
			}

			sprintf(gps_test_info, "%d,", tracked);
			strcat(gps_test_info, strbuf);
			strcat(gps_test_info, "\n");
			sprintf(strbuf, "Longitude:%f, Latitude:%f\n", evt->pvt.longitude, evt->pvt.latitude);
			strcat(gps_test_info, strbuf);
			sprintf(strbuf, "fix time:%d", gps_local_time/1000);
			strcat(gps_test_info, strbuf);
			gps_test_update_flag = true;
			
			//LOG_INF("%s\n",gps_test_info);
			//UpdataTestGPSInfo();
			//TestGPSShowInfor();
		}		
		else
		{
			sprintf(tmpbuf, "Longitude:%f, Latitude:%f", evt->pvt.longitude, evt->pvt.latitude);
			LOG_INF("%s\n",tmpbuf);
		
			memcpy(&gps_pvt_data, &(evt->pvt), sizeof(evt->pvt));
		}
		break;
		
	case GPS_EVT_NMEA:
		/* Don't spam logs */
		LOG_INF("GPS_EVT_NMEA\n");
		break;
		
	case GPS_EVT_NMEA_FIX:
		LOG_INF("GPS_EVT_NMEA_FIX");

		if(gps_fix_time == 0)
		{
			gps_fix_time = k_uptime_get();
			gps_local_time = gps_fix_time-gps_start_time;
		}
		
		if(!test_gps_flag)
		{
			LOG_INF("Position fix with NMEA data, fix time:%d", gps_local_time);
			LOG_INF("NMEA:%s\n", evt->nmea.buf);
		
			APP_Ask_GPS_off();

			if(k_timer_remaining_get(&app_wait_gps_timer) > 0)
				k_timer_stop(&app_wait_gps_timer);

			k_timer_start(&app_send_gps_timer, K_MSEC(1000), NULL);
		}
		break;
		
	case GPS_EVT_OPERATION_BLOCKED:
		LOG_INF("GPS_EVT_OPERATION_BLOCKED\n");
		break;
		
	case GPS_EVT_OPERATION_UNBLOCKED:
		LOG_INF("GPS_EVT_OPERATION_UNBLOCKED\n");
		break;
		
	case GPS_EVT_AGPS_DATA_NEEDED:
		LOG_INF("GPS_EVT_AGPS_DATA_NEEDED\n");
		k_work_submit_to_queue(app_work_q,
				       &send_agps_request_work);
		break;
		
	case GPS_EVT_ERROR:
		LOG_INF("GPS_EVT_ERROR\n");
		break;
		
	default:
		break;
	}
}

void GPS_init(struct k_work_q *work_q)
{
	app_work_q = work_q;

	k_work_init(&send_agps_request_work, send_agps_request);

	gps_control_init(app_work_q, gps_handler);
}

[Albrecht Markus Schellenberger]

Hello,

My assumption here would be that the GPS socket is blocked by the LTE socket, since LTE always is prioritised.

Could you please check your network registration status (or alternatively read modem parameters)? It would be good to confirm that the network has allowed the device entering PSM.

Another idea could be enabling modem sleep and/or periodic TAU notifications.

Regards,

Markus

[duxinglang]

Yes, I registered the NB network when the system was initialized, but because of the SIM card, the Modem returned a connection failure, so I closed the modem, and then reset AT+CFUN=1 to turn on the modem when the GPS was needed. I don't think there should be any NB operation to block the GPS in this case.  

[Albrecht Markus Schellenberger]

duxinglang said:

but because of the SIM card, the Modem returned a connection failure, so I closed the modem, and then reset AT+CFUN=1 to turn on the modem when the GPS was needed.

I do honestly not think that this sounds about right. What kind of connection failure does the modem return?

duxinglang said:

I don't think there should be any NB operation to block the GPS in this case.  

The thing is that, as long as the LTE socket is not in RRC idle, the GPS socket will not run.

Regards,

Markus

[duxinglang]

I'm sorry I didn't make it clear. What I meant was that the device failed to register with the NB network through the modem because the SIM was not activated. In order to prevent the modem from automatically registering the network repeatedly, I turned off the modem and then turned it back on when the GPS needed to be started.

[Albrecht Markus Schellenberger]

Thanks for elaborating!

duxinglang said:

In order to prevent the modem from automatically registering the network repeatedly, I turned off the modem and then turned it back on when the GPS needed to be started.

Turning on the modem with AT+CFUN=1 will also enable the LTE socket which will block the GPS socket from running during the connection attempt(s).

I would recommend you instead to turn on the modem with AT+CFUN=31 or disable the LTE socket using AT%XSYSTEMMODE=0,0,1,0

Regards,

Markus