AGPS with SUPL with MQTT_Simple example

[Nahan_Trogn]

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]

Hello, 

Error: -13 that you get, translates to 

#define	EACCES 13	/* Permission denied */

The GPS receiver supports GPS L1 C/A reception. Operation is time multiplexed with LTE modem, and it is possible to obtain the GPS position either while the LTE is in RRC Idle mode or power saving mode (PSM), or when the LTE modem is completely deactivated.

Please make sure that your device is in PSM or deactivated before starting GPS.

Kind regards,
Øyvind

[Nahan_Trogn]

Hi,

In start function, I success enable PSM mode, and receive feedback "PSM parameter update: TAU: 15000, Active time: 6". How to know  my device is in PSM? Are there any events that I can check?

I see that, in PSM mode, there is sometimes RCC in connected mode, does this affect GPS? So I only need to check RCC whether in idle mode?

[Øyvind]

Hello, 

You can use e.g. AT+CSCON to check the signaling connection status to check mode parameter, either Idle or Connected. The former is what you will need to check. 

Have a look at the LTE Link Controller (nrf\include\modem\lte_lc.h) and the GPS sample, for an example on how this is handled (nrf\samples\nrf9160\gps\src\main.c)

[Nahan_Trogn]

In my case, I want to use AGPS, so I still wait for RRC Idle? I try to start AGPS when RRC in Idle mode, but the same problem. I wait for RRC to announce Idle, then continue to wait 25-30 seconds, and start AGPS, sometimes SUPL success, many times fail.

My problem is I don't know when to do the first start for AGPS to obtain SUPL data.

I use nRF9160 GPS driver [experimental].

[Øyvind]

Nahan_Trogn said:

Idle, then continue to wait 25-30 seconds, and start AGPS, sometimes SUPL success, many times fail.

 Can you provide some information on what is failing

Nahan_Trogn said:

My problem is I don't know when to do the first start for AGPS to obtain SUPL data.

Does the default AGPS sample work?  

Have you tried to start with e.g. AGPS sample and add MQTT to this?

[Nahan_Trogn]

This is my log file. I manually start AGPS by button, when seeing RRC Idle Event. I achieve 2 successes.2021-06-02T14_24_18.010Z-log.txt

The Default AGPS example and GPS example work well. I combine AGPS to MQTT_Simple base on the AGPS example.