AGPS with SUPL with MQTT_Simple example

Question

Hi, 
 I use MQTT_Simple example with AGPS feature; 
 I add 3 functions, one for init GPS, one for start GPS, and the last for A_GPS request. 
 static void gps_control_init(void)
{
 int err;

 gps_dev = device_get_binding(CONFIG_NRF9160_GPS_DEV_NAME);
 if (gps_dev == NULL) {
 LOG_ERR("Could not get %s device",
 log_strdup(CONFIG_NRF9160_GPS_DEV_NAME));
 return -ENODEV;
 }

 err = gps_init(gps_dev, gps_handler);
 if (err) {
 LOG_ERR("Could not initialize GPS, error: %d", err);
 return err;
 }
}

static void start(void)
{
 int err;
 struct gps_config gps_cfg = {
 .nav_mode = GPS_NAV_MODE_PERIODIC,
 .power_mode = GPS_POWER_MODE_DISABLED,
 .timeout = 360,
 .interval = 360 +
 30,
 .priority = true,
 };

 if (gps_dev == NULL) {
 LOG_ERR("GPS controller is not initialized properly");
 return;
 }

 LOG_INF("Enabling PSM");

 err = lte_lc_psm_req(true);
 if (err) {
 LOG_ERR("PSM request failed, error: %d", err);
 } else {
 LOG_INF("PSM enabled");
 }

 err = gps_start(gps_dev, &gps_cfg);
 if (err) {
 LOG_ERR("Failed to enable GPS, error: %d", err);
 return;
 }

}

static void on_agps_needed(struct gps_agps_request request)
{
	int err;

	err = gps_agps_request(request, GPS_SOCKET_NOT_PROVIDED);
	if (err) {
 LOG_ERR("Failed to request A-GPS data, error: %d", err);
 return;
	}
} 
 I call Init after "MQTT client connected", and start GPS by button_handler. 
 When it runs, an error occurs:

I used nRF9160 GPS driver [experimental], Ubuntu, ncs v1.5.1

Øyvind · Answer

Hi, I'm trying to find a solution to this issue, and am currently working with our developers. 
 The initial question is: Have you tried implementing MQTT to the AGPS sample? If this sample works as intended, then maybe that would be an easier work-around. Our SUPL expert had a look at you case, and says: 
 It seems that device gets some A-GPS data and writes that to the modem. It seems as if it couldn't read all of the data or something like that. 
 It takes a long time, so it can't be executed for example in the button handler directly. It should be ran in a separate thread. And the proper way to do it would be to fetch A-GPS data when GNSS asks for it. GPS driver sends event GPS_EVT_AGPS_DATA_NEEDED when it needs A-GPS data. That event contains a structure of type gps_agps_request which indicates what kind of A-GPS data GNSS needs. They should check the AGPS sample, it triggers the fetching of A-GPS data when GPS_EVT_AGPS_DATA_NEEDED is received by the event handler. 
 
 Kind regards, Øyvind

AGPS with SUPL with MQTT_Simple example

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