I am trying to implement GPS code.

[Gunjan Yadav]

I am trying to implement GPS code in the nrf9160 but I cant find the function nrf_modem_gnss_init(); to initialize GNSS inside the modem in , is it being initialised within nrf_modem_gnss_start() function internally ?   please help on this.

[Hakon]

You should check if the LNA gets properly enabled. Since you are using a regular GPIO pin instead of COEX0, there can potentially be issues.

GNSS gets started and is receiving PVT notifications once a second, so it does not look like a GNSS API issue.

[Gunjan Yadav]

This is an internal GPS setup and has external on-board antenna attached to it. 

I can see voltages around D1(2.489 at cathode ) , D2 (2.673 at cathode ) which further goes to c1(2.48), c2(2.49)  and c3(2.67), c4(2.67) which are sufficient to power up LNA. 

Is there anything else I am missing in the code ?

Also coex is used for coexistence of LTE along with GNSS. Here I am using GNSS mode only in the code. 

 

Hakon 

[Gunjan Yadav]

Hi Hakon  I have tried implementing the GPS functionality on nrf9160DK board on this it is working fine and I am able to get the coordinates. but I have not written any code line explicitly to enable the LNA in it.

Can you please confirn how this is being taken care internally ? Is it enabled by COEX or MAGPIO and why it's not needed to enable COEX / MAGPIO  explicitly for nrf9160DK board?

[Hakon]

Gunjan Yadav said:

Can you please confirn how this is being taken care internally ? Is it enabled by COEX or MAGPIO and why it's not needed to enable COEX / MAGPIO  explicitly for nrf9160DK board?

When building for the nRF9160 DK, the Modem antenna library (CONFIG_MODEM_ANTENNA) gets enabled by default. The Modem antenna library configures COEX0 correctly for the DK based on whether CONFIG_MODEM_ANTENNA_GNSS_ONBOARD or CONFIG_MODEM_ANTENNA_GNSS_EXTERNAL is enabled. LNA is enabled when using the onboard antenna, and disabled when using an external antenna.

[Gunjan Yadav]

Hi Hakon  Can you please suggest how to explicitly enable coex pin ? We have made some changes in the board and now LNA is connected to COEX0 but when I am trying to run the apis as above it is not being taken care internally and LNA may not be getting powered up. Can you please suggest how to do this now ?

[Hakon]

Modem can be configured to enable COEX0 pin when GNSS is used with the following AT command: AT%XCOEX0=1,1,1565,1586

The command should be sent during startup, before enabling RF (for example AT+CFUN=1).

[Gunjan Yadav]

Hi Team,

We have tried as per your suggestion that configured COEX0 pin as below but still unable to get longitude and latitude. Can you please provide your inputs to fix this issue. We have provided our schematics and code below.

at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XCOEX0=1,1,1565,1586");

Note: We are configuring AT%XCOEX0 before AT+CFUN=0. Please see below code snippet. And we are not making AT+CFUN=1 specifically, do we need to do this? If yes, after which command?

Query: We are configuring AT+CFUN=31, is this a correct command?

#define AT_CFUN_GNSS_ONLY_CMD                        "AT+CFUN=31\r\n"

Code snippet:

 /* Query current system mode to avoid unnecessary writes */

        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XSYSTEMMODE?\r\n");

        if (at_err)

        {

            int type = nrf_modem_at_err_type(at_err);

            int code = nrf_modem_at_err(at_err);

            LOG_WRN("XSYSTEMMODE? failed (type=%d code=%d), proceeding to set", type, code);

        }

            memset(rsp, 0, sizeof(rsp));

            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XCOEX0=1,1,1565,1586");

            if (at_err)

            {

                LOG_WRN("XCOEX0 set failed: type=%d code=%d ret=%d",

                        nrf_modem_at_err_type(at_err), nrf_modem_at_err(at_err), at_err);

            }

            else

            {

                LOG_INF("XCOEX0 configured for RF coexistence");

            }

        /* Go to minimum or offline functionality before changing system mode */

        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_OFF_RADIO_CMD);

        if (at_err)

        {

            int type = nrf_modem_at_err_type(at_err);

            int code = nrf_modem_at_err(at_err);

            LOG_WRN("CFUN=0 failed: type=%d code=%d ret=%d, trying CFUN=4", type, code, at_err);

            memset(rsp, 0, sizeof(rsp));

            /* Try offline mode */

            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_OFFLINE_CMD);

            if (at_err)

            {

                type = nrf_modem_at_err_type(at_err);

                code = nrf_modem_at_err(at_err);

                LOG_ERR("CFUN=4 failed: type=%d code=%d ret=%d", type, code, at_err);

                return at_err;

            }

        }

        /* Small delay to let modem settle */

        k_msleep(200);

        /* Set GNSS-only system mode */

        memset(rsp, 0, sizeof(rsp));

        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_COMMAND_SYS_GNSS_ONLY_MODE);

        if (at_err)

        {

            int type = nrf_modem_at_err_type(at_err);

            int code = nrf_modem_at_err(at_err);

            LOG_ERR("XSYSTEMMODE GNSS-only failed: type=%d code=%d ret=%d", type, code, at_err);

            return at_err;

        }

        /* Enter GNSS-only functional mode */

        memset(rsp, 0, sizeof(rsp));

        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_GNSS_ONLY_CMD);

        if (at_err)

        {

            int type = nrf_modem_at_err_type(at_err);

            int code = nrf_modem_at_err(at_err);

            LOG_ERR("CFUN GNSS-only failed: type=%d code=%d ret=%d", type, code, at_err);

            return at_err;

        }

Schematics:

Firmware files:

Fullscreen gps.c Download

#include <zephyr/kernel.h>
#include <zephyr/logging/log.h>
#include <zephyr/drivers/gpio.h>
#include <nrf_modem_gnss.h>
#include <modem/nrf_modem_lib.h>
#include <nrf_modem_at.h>
#include "AT_CMD/at_cmd.h"
#include <modem/lte_lc.h>
#include "modem/modem.h"

#include "gps.h"

#if IS_ENABLED(CONFIG_LTE_LINK_CONTROL)
#endif

/* Get gps_en node from devicetree */
#define GPS_EN_NODE DT_NODELABEL(gps_enable)

/* GPIO specification for GPS enable */
static const struct gpio_dt_spec gps_en = GPIO_DT_SPEC_GET(GPS_EN_NODE, gpios);

LOG_MODULE_REGISTER(gnss_app, LOG_LEVEL_INF);

static struct nrf_modem_gnss_pvt_data_frame pvt_data;

#define ENABLE_GNSS_RF_ROUTING 0

static int sv_in_view(const struct nrf_modem_gnss_pvt_data_frame *p)
{
    int count = 0;
    for (int i = 0; i < NRF_MODEM_GNSS_MAX_SATELLITES; i++)
    {
        if (p->sv[i].sv > 0)
        {
            count++;
        }
    }
    return count;
}

static int sv_used_in_fix(const struct nrf_modem_gnss_pvt_data_frame *p)
{
    int count = 0;
    for (int i = 0; i < NRF_MODEM_GNSS_MAX_SATELLITES; i++)
    {
        if (p->sv[i].flags & NRF_MODEM_GNSS_SV_FLAG_USED_IN_FIX)
        {
            count++;
        }
    }
    return count;
}

static void gnss_event_handler(int event)
{
    int err;

    static bool first_log = true;

    switch (event)
    {
    case NRF_MODEM_GNSS_EVT_PVT:
        err = nrf_modem_gnss_read(&pvt_data, sizeof(pvt_data), NRF_MODEM_GNSS_DATA_PVT);
        if (err)
        {
            LOG_ERR("Failed to read PVT data, err=%d", err);
            return;
        }

        if (first_log)
        {
            first_log = false;
            LOG_INF("GNSS PVT struct size=%u", (unsigned)sizeof(pvt_data));
        }
        LOG_INF("PVT flags=0x%08x", pvt_data.flags);

        for(int i = 0; i < NRF_MODEM_GNSS_MAX_SATELLITES; i++)
        {
            if(pvt_data.sv[i].sv >0)
            {

                 int used_in_fix = (pvt_data.sv[i].flags & NRF_MODEM_GNSS_SV_FLAG_USED_IN_FIX) ? 1 : 0;


                 
                 int      sv_id       = (int)pvt_data.sv[i].sv;
                 double   cn0         = (double)pvt_data.sv[i].cn0;
                 uint8_t  used_in_fix1 = (pvt_data.sv[i].flags & NRF_MODEM_GNSS_SV_FLAG_USED_IN_FIX) ? 1 : 0;
                 uint16_t flags       = (uint16_t)pvt_data.sv[i].flags;

                 LOG_INF("SV %d C/N0=%.1f used=%d flags=0x%04x",
                 (int)pvt_data.sv[i].sv,
                 (double)pvt_data.sv[i].cn0,
                 used_in_fix,
                 (unsigned)pvt_data.sv[i].flags);

            }
        
        }

        /* Valid fix if 'flags' contains FIX_VALID */
        if (pvt_data.flags & NRF_MODEM_GNSS_PVT_FLAG_FIX_VALID)
        {
            LOG_INF(" FIX: lat=%.6f lon=%.6f alt=%.1f(m) acc=%.1f(m) sv_used=%d sv_view=%d",
                    pvt_data.latitude,
                    pvt_data.longitude,
                    pvt_data.altitude,
                    pvt_data.accuracy,
                    sv_used_in_fix(&pvt_data),
                    sv_in_view(&pvt_data));

            LOG_INF("Speed=%.2f(m/s) Heading=%.2f(deg) HDOP=%.2f",
                    pvt_data.speed,
                    pvt_data.heading,
                    pvt_data.hdop);

            /* Stop after first valid fix (change this behavior as needed) */
            // gps_stop();
            // LOG_INF("GNSS stopped after first fix.");
        }
        else
        {
            LOG_INF("PVT: searching... sv_view=%d acc=%.1f(m) flags=0x%08x",
                    sv_in_view(&pvt_data), pvt_data.accuracy, pvt_data.flags);
        }
        break;

    case NRF_MODEM_GNSS_EVT_FIX:
        /* FIX event indicates a fix was achieved (PVT will also carry details) */
        LOG_INF("NRF_MODEM_GNSS_EVT_FIX");
        break;

    case NRF_MODEM_GNSS_EVT_NMEA:
        /* Optional: read NMEA sentences if enabled */
        {
            char nmea[256];
            err = nrf_modem_gnss_read(nmea, sizeof(nmea), NRF_MODEM_GNSS_DATA_NMEA);
            if (err > 0)
            {
                /* 'err' is number of bytes read */
                nmea[MIN(err, (int)sizeof(nmea) - 1)] = '\0';
                LOG_INF("NMEA: %s", nmea);
            }
        }
        break;

        /* A-GNSS request handling (only if headers provide these enums) */
#if defined(NRF_MODEM_GNSS_EVT_AGPS_REQ) && defined(NRF_MODEM_GNSS_DATA_AGPS_REQ)
    case NRF_MODEM_GNSS_EVT_AGPS_REQ:
    {
        struct nrf_modem_gnss_agps_data_request req = (struct nrf_modem_gnss_agps_data_request){0};
        err = nrf_modem_gnss_read(&req, sizeof(req), NRF_MODEM_GNSS_DATA_AGPS_REQ);
        if (err)
        {
            LOG_WRN("A-GNSS req read failed: %d", err);
        }
        else
        {
            LOG_INF("A-GNSS requested: utc=%u almanac=%u eph=%u klob=%u neq=%u time=%u pos=%u iono=%u",
                    req.utc, req.almanac, req.ephemeris, req.klobuchar,
                    req.nequick, req.system_time, req.position, req.iono);
            LOG_INF("Consider fetching assistance (nRF Cloud/SUPL) and injecting.");
        }
        break;
    }
#endif

    default:
        LOG_INF("GNSS event: %d", event);
        break;
    }
}

int gnss_setup_and_start(void)
{
    int err;

    LOG_INF("Entered  gnss_setup_and_start starting function");
    /* Ensure GPS_EN GPIO device is ready */
    #if 0
    if (!device_is_ready(gps_en.port))
    {
        LOG_ERR("GPS_EN GPIO not ready");
        return -ENODEV;
    }

    /* Configure GPS_EN pin as output and turn GPS ON */
    err = gpio_pin_configure_dt(&gps_en, GPIO_OUTPUT_ACTIVE);
    if (err)
    {
        LOG_ERR("Failed to configure GPS_EN");
        return err;
    }

    err = gpio_pin_set_dt(&gps_en, 1);
    if (err)
    {
        LOG_ERR("Failed to set GPS_EN");
        return err;
    }

    #endif

    LOG_INF("GPS powered ON");

    /* LNA/antenna warm-up */
    k_msleep(50);

    /* Ensure modem is switched to GNSS-only mode before GNSS APIs */
    {
        char rsp[256] = {0};
        int at_err;

        /* Query current system mode to avoid unnecessary writes */
        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XSYSTEMMODE?\r\n");
        if (at_err)
        {
            int type = nrf_modem_at_err_type(at_err);
            int code = nrf_modem_at_err(at_err);
            LOG_WRN("XSYSTEMMODE? failed (type=%d code=%d), proceeding to set", type, code);
        }


            memset(rsp, 0, sizeof(rsp));
            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XCOEX0=1,1,1565,1586");
            if (at_err)
            {
                LOG_WRN("XCOEX0 set failed: type=%d code=%d ret=%d",
                        nrf_modem_at_err_type(at_err), nrf_modem_at_err(at_err), at_err);
            }
            else
            {
                LOG_INF("XCOEX0 configured for RF coexistence");
            }


        /* Go to minimum or offline functionality before changing system mode */
        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_OFF_RADIO_CMD);
        if (at_err)
        {
            int type = nrf_modem_at_err_type(at_err);
            int code = nrf_modem_at_err(at_err);
            LOG_WRN("CFUN=0 failed: type=%d code=%d ret=%d, trying CFUN=4", type, code, at_err);
            memset(rsp, 0, sizeof(rsp));
            /* Try offline mode */
            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_OFFLINE_CMD);
            if (at_err)
            {
                type = nrf_modem_at_err_type(at_err);
                code = nrf_modem_at_err(at_err);
                LOG_ERR("CFUN=4 failed: type=%d code=%d ret=%d", type, code, at_err);
                return at_err;
            }
        }

        /* Small delay to let modem settle */
        k_msleep(200);

        /* Set GNSS-only system mode */
        memset(rsp, 0, sizeof(rsp));
        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_COMMAND_SYS_GNSS_ONLY_MODE);
        if (at_err)
        {
            int type = nrf_modem_at_err_type(at_err);
            int code = nrf_modem_at_err(at_err);
            LOG_ERR("XSYSTEMMODE GNSS-only failed: type=%d code=%d ret=%d", type, code, at_err);
            return at_err;
        }

        /* Enter GNSS-only functional mode */
        memset(rsp, 0, sizeof(rsp));
        at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", AT_CFUN_GNSS_ONLY_CMD);
        if (at_err)
        {
            int type = nrf_modem_at_err_type(at_err);
            int code = nrf_modem_at_err(at_err);
            LOG_ERR("CFUN GNSS-only failed: type=%d code=%d ret=%d", type, code, at_err);
            return at_err;
        }
        LOG_INF("Modem set to GNSS-only mode");

        /* GNSS RF routing and coexistence */
        if (ENABLE_GNSS_RF_ROUTING)
        {
            memset(rsp, 0, sizeof(rsp));
            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XMAGPIO=1,1,1,7,0,0");
            if (at_err)
            {
                LOG_WRN("XMAGPIO set failed: type=%d code=%d ret=%d",
                        nrf_modem_at_err_type(at_err), nrf_modem_at_err(at_err), at_err);
            }
            else
            {
                LOG_INF("XMAGPIO configured for GNSS antenna/LNA");
            }
            memset(rsp, 0, sizeof(rsp));
            at_err = nrf_modem_at_cmd(rsp, sizeof(rsp), "%s", "AT%XCOEX0=1,1,0");
            if (at_err)
            {
                LOG_WRN("XCOEX0 set failed: type=%d code=%d ret=%d",
                        nrf_modem_at_err_type(at_err), nrf_modem_at_err(at_err), at_err);
            }
            else
            {
                LOG_INF("XCOEX0 configured for RF coexistence");
            }
        }
        else
        {
            LOG_INF("Skipping XMAGPIO/XCOEX0");
        }
    }
    // uint32_t mask = NRF_MODEM_GNSS_DELETE_EPHEMERIDES |
    //                 NRF_MODEM_GNSS_DELETE_ALMANACS |
    //                 NRF_MODEM_GNSS_DELETE_IONO_CORRECTION_DATA |
    //                 NRF_MODEM_GNSS_DELETE_UTC_DATA |
    //                 NRF_MODEM_GNSS_DELETE_LAST_GOOD_FIX |
    //                 NRF_MODEM_GNSS_DELETE_GPS_TOW;

    // //delets the non-volatile data in the modem to ensure a cold start (clear ephemeris/almanac/assist data for testing)                
    // err = nrf_modem_gnss_nv_data_delete(mask);
    // if (err)
    // {
    //     LOG_WRN("GNSS NV data delete failed: %d", err);
    //     /* Not fatal—continue */
    // }
    // else
    // {
    //     LOG_INF("GNSS NV data cleared (cold start).");
    // }

    /* Register GNSS event handler */
    err = nrf_modem_gnss_event_handler_set(gnss_event_handler);
    if (err)
    {
        LOG_ERR("Failed to set GNSS event handler, err=%d", err);
        return err;
    }

    /* Configure fix interval / retry:
     * - fix_interval: time between starts of consecutive fix attempts (seconds)
     *   0 = continuous tracking
     * - fix_retry: how long GNSS tries to get a fix before sleeping (seconds)
     *   0 = try forever
     */
    err = nrf_modem_gnss_fix_interval_set(0); /* 0 = continuous tracking */
    if (err)
    {
        LOG_ERR("fix_interval_set failed: %d", err);
        return err;
    }

    err = nrf_modem_gnss_fix_retry_set(0); /* 0 = try forever for cold start */
    if (err)
    {
        LOG_ERR("fix_retry_set failed: %d", err);
        return err;
    }

    /* Enable NMEA sentences for visibility (GGA/RMC + satellites GSV/GSA) */
    {
        uint16_t nmea_mask = NRF_MODEM_GNSS_NMEA_GGA_MASK |
                             NRF_MODEM_GNSS_NMEA_RMC_MASK |
                             NRF_MODEM_GNSS_NMEA_GSV_MASK |
                             NRF_MODEM_GNSS_NMEA_GSA_MASK;
        err = nrf_modem_gnss_nmea_mask_set(nmea_mask);
        if (err)
        {
            LOG_WRN("nmea_mask_set failed: %d", err);
        }

        /* Optional GNSS performance tuning */
        (void)nrf_modem_gnss_use_case_set(NRF_MODEM_GNSS_USE_CASE_MULTIPLE_HOT_START |
                            NRF_MODEM_GNSS_USE_CASE_LOW_ACCURACY);

        // Increase warm‑up time if using an external active antenna or LNA, as they may require more time to stabilize and provide optimal performance.
        k_msleep(50);

        /* Start GNSS */
        err = nrf_modem_gnss_start();
        if (err)
        {
            LOG_ERR("Failed to start GNSS, err=%d", err);
            return err;
        }

        LOG_INF("GNSS started.");

        return 0;
    }
}

/* Stop GPS */
void gps_stop(void)
{
    LOG_INF("Stopping GPS");

    nrf_modem_gnss_stop();
}

    

gps.h

at_cmd.h

Regards,

Gunjan

[Hakon]

Gunjan Yadav said:

We are configuring AT%XCOEX0 before AT+CFUN=0.

As long as you send nothing before this and there is no modem activity before issuing this command it's fine.

Gunjan Yadav said:

Query: We are configuring AT+CFUN=31, is this a correct command?

This should also be fine.

[Gunjan Yadav]

cl5gMCU&hvppGPS 1.txtHVPP_firmware_on_CL5G_HW_test2.txt

[Tommi Kangas]

Hi,

I checked the modem log, but in that log the COEX0 pin is not configured correctly, so the LNA is not enabled.

Please make sure that the pin configuration is correct (you can use the AT command AT%XCOEX0=1,1,1565,1586 mentioned earlier) and that it's configured before the RF is enabled (latest before GNSS start). Can you capture a new modem log with the correct configuration, so I can have a look from modem point of view?

Best regards,
Tommi

[Karthik]

Hi,

   If you see the above picture, we are configuring COEX0 pin before the RF is enabled. Please go through the code gps.c in the attachment.

You referred terminal_logsOpen1.log for modem logs ?

Regards,

Karthik.

[Tommi Kangas]

Hi,

I'm referring to Modem_logsOpen1.bin. It was taken before COEX0 configuration was fixed. Please take a new modem log with the current implementation which configures COEX0 correctly.

BR,
Tommi