nRF9160 - Multiplexed ("concurrent") Cellular and GNSS activity seems unstable

[sjacobsen]

Using the GPS sample application as a base, I examined the behavior of "concurrent" cellular and GNSS.  I enabled cellular with at+cfun=21 after a GPS fix was obtained. I also enabled PSM with AT+CPSMS=1, but the network did not seem to grant PSM.    I also added this to the GNSS configuration to attempt to enable GNSS power save:

...

        nrf_gnss_power_save_mode_t psm_mask = NRF_GNSS_PSM_DUTY_CYCLING_POWER;

...

retval = nrf_setsockopt(gnss_fd,
NRF_SOL_GNSS,
NRF_SO_GNSS_POWER_SAVE_MODE,
&psm_mask,
sizeof(psm_mask));
if (retval != 0) {
printk("Failed to set psm mask\n");
return -1;
}

While monitoring the module states with a current sensor, it was clear that the cellular module would drop into RRC idle with 1.28s DRX intervals.   GNSS stayed in high power mode, ~42 mA.  Oddly, though, the cellular modem frequently lost sync with the network and performed a lengthy carrier search, say 20-30 seconds.  In contrast, when I run the at_client app, the network attachment is rock solid and the modem stays in RRC idle, maintaining sync and never re-searching for a carrier.

Is it possible the "concurrent" activity of the cellular and GNSS radios or sockets is causing the cellular modem to lose sync with the network?

I will repeat with a CMW500 so that signal levels are identical between the GPS sample application and at_client application.

I've attached my modified GPS sample application:

Fullscreen 8865.main.c Download

/*
 * Copyright (c) 2019 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-BSD-5-Clause-Nordic
 */

#include <zephyr.h>
#include <nrf_socket.h>
#include <net/socket.h>
#include <stdio.h>
#include <modem/at_cmd.h>
#include <modem/at_notif.h>
//#define CONFIG_SUPL_CLIENT_LIB
#ifdef CONFIG_SUPL_CLIENT_LIB
#include <supl_os_client.h>
#include <supl_session.h>
#include "supl_support.h"
#endif

#define AT_XSYSTEMMODE      "AT\%XSYSTEMMODE=1,0,1,0"
#define AT_ACTIVATE_GPS     "AT+CFUN=31"
#define AT_ACTIVATE_LTE     "AT+CFUN=21"
#define AT_DEACTIVATE_LTE   "AT+CFUN=20"
#define AT_ACTIVATE_ALL     "AT+CFUN=1"
#define AT_PSM  "AT+CPSMS=1"

#define GNSS_INIT_AND_START 1
#define GNSS_STOP           2
#define GNSS_RESTART        3

#define AT_CMD_SIZE(x) (sizeof(x) - 1)

#ifdef CONFIG_BOARD_NRF9160DK_NRF9160NS
#define AT_MAGPIO      "AT\%XMAGPIO=1,0,0,1,1,1574,1577"
#ifdef CONFIG_GPS_SAMPLE_ANTENNA_ONBOARD
#define AT_COEX0       "AT\%XCOEX0=1,1,1565,1586"
#elif CONFIG_GPS_SAMPLE_ANTENNA_EXTERNAL
#define AT_COEX0       "AT\%XCOEX0"
#endif
#endif /* CONFIG_BOARD_NRF9160DK_NRF9160NS */

#ifdef CONFIG_BOARD_THINGY91_NRF9160NS
#define AT_MAGPIO      "AT\%XMAGPIO=1,1,1,7,1,746,803,2,698,748,2,1710,2200," \
			"3,824,894,4,880,960,5,791,849,7,1565,1586"
#ifdef CONFIG_GPS_SAMPLE_ANTENNA_ONBOARD
#define AT_COEX0       "AT\%XCOEX0=1,1,1565,1586"
#elif CONFIG_GPS_SAMPLE_ANTENNA_EXTERNAL
#define AT_COEX0       "AT\%XCOEX0"
#endif
#endif /* CONFIG_BOARD_THINGY91_NRF9160NS */

static const char update_indicator[] = {'\\', '|', '/', '-'};
static const char *const at_commands[] = {
	AT_XSYSTEMMODE,
#if defined(CONFIG_BOARD_NRF9160DK_NRF9160NS) || \
	defined(CONFIG_BOARD_THINGY91_NRF9160NS)
	AT_MAGPIO,
	AT_COEX0,
#endif
	AT_ACTIVATE_GPS
        //AT_ACTIVATE_LTE
        //AT_ACTIVATE_ALL
};

static const char *const at_commands_xtra[] = {
	AT_PSM,
        AT_ACTIVATE_LTE
};


static int                   gnss_fd;
static char                  nmea_strings[10][NRF_GNSS_NMEA_MAX_LEN];
static uint32_t                 nmea_string_cnt;

static bool                  got_fix;
static bool                  cellular_off;
static uint64_t                 fix_timestamp;
static nrf_gnss_data_frame_t last_pvt;

K_SEM_DEFINE(lte_ready, 0, 1);

void bsd_recoverable_error_handler(uint32_t error)
{
	printf("Err: %lu\n", (unsigned long)error);
}

static int setup_modem(void)
{
	for (int i = 0; i < ARRAY_SIZE(at_commands); i++) {

		if (at_cmd_write(at_commands[i], NULL, 0, NULL) != 0) {
			return -1;
		}
	}

	return 0;
}

static int setup_modem_xtra(void)
{
	for (int i = 0; i < ARRAY_SIZE(at_commands_xtra); i++) {

		if (at_cmd_write(at_commands_xtra[i], NULL, 0, NULL) != 0) {
			return -1;
		}
	}

	return 0;
}

#ifdef CONFIG_SUPL_CLIENT_LIB
/* Accepted network statuses read from modem */
static const char status1[] = "+CEREG: 1";
static const char status2[] = "+CEREG:1";
static const char status3[] = "+CEREG: 5";
static const char status4[] = "+CEREG:5";

static void wait_for_lte(void *context, const char *response)
{
	if (!memcmp(status1, response, AT_CMD_SIZE(status1)) ||
		!memcmp(status2, response, AT_CMD_SIZE(status2)) ||
		!memcmp(status3, response, AT_CMD_SIZE(status3)) ||
		!memcmp(status4, response, AT_CMD_SIZE(status4))) {
		k_sem_give(&lte_ready);
	}
}

static int activate_lte(bool activate)
{
	if (activate) {
		if (at_cmd_write(AT_ACTIVATE_LTE, NULL, 0, NULL) != 0) {
			return -1;
		}

		at_notif_register_handler(NULL, wait_for_lte);
		if (at_cmd_write("AT+CEREG=2", NULL, 0, NULL) != 0) {
			return -1;
		}

		k_sem_take(&lte_ready, K_FOREVER);

		at_notif_deregister_handler(NULL, wait_for_lte);
		if (at_cmd_write("AT+CEREG=0", NULL, 0, NULL) != 0) {
			return -1;
		}
	} else {
		if (at_cmd_write(AT_DEACTIVATE_LTE, NULL, 0, NULL) != 0) {
			return -1;
		}
	}

	return 0;
}
#endif

static int gnss_ctrl(uint32_t ctrl)
{
	int retval;

	nrf_gnss_fix_retry_t    fix_retry    = 0;
	nrf_gnss_fix_interval_t fix_interval = 1;
	nrf_gnss_delete_mask_t	delete_mask  = 0;
	nrf_gnss_nmea_mask_t	nmea_mask    = NRF_GNSS_NMEA_GSV_MASK |
					       NRF_GNSS_NMEA_GSA_MASK |
					       NRF_GNSS_NMEA_GLL_MASK |
					       NRF_GNSS_NMEA_GGA_MASK |
					       NRF_GNSS_NMEA_RMC_MASK;
        nrf_gnss_power_save_mode_t psm_mask = NRF_GNSS_PSM_DUTY_CYCLING_POWER;

	if (ctrl == GNSS_INIT_AND_START) {
		gnss_fd = nrf_socket(NRF_AF_LOCAL,
				     NRF_SOCK_DGRAM,
				     NRF_PROTO_GNSS);

		if (gnss_fd >= 0) {
			printk("GPS Socket created\n");
		} else {
			printk("Could not init socket (err: %d)\n", gnss_fd);
			return -1;
		}

		retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_FIX_RETRY,
					&fix_retry,
					sizeof(fix_retry));
		if (retval != 0) {
			printk("Failed to set fix retry value\n");
			return -1;
		}

		retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_FIX_INTERVAL,
					&fix_interval,
					sizeof(fix_interval));
		if (retval != 0) {
			printk("Failed to set fix interval value\n");
			return -1;
		}

		retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_NMEA_MASK,
					&nmea_mask,
					sizeof(nmea_mask));
		if (retval != 0) {
			printk("Failed to set nmea mask\n");
			return -1;
		}

                retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_POWER_SAVE_MODE,
					&psm_mask,
					sizeof(psm_mask));
		if (retval != 0) {
			printk("Failed to set psm mask\n");
			return -1;
		}
	}

	if ((ctrl == GNSS_INIT_AND_START) ||
	    (ctrl == GNSS_RESTART)) {
		retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_START,
					&delete_mask,
					sizeof(delete_mask));
		if (retval != 0) {
			printk("Failed to start GPS\n");
			return -1;
		}
	}

	if (ctrl == GNSS_STOP) {
		retval = nrf_setsockopt(gnss_fd,
					NRF_SOL_GNSS,
					NRF_SO_GNSS_STOP,
					&delete_mask,
					sizeof(delete_mask));
		if (retval != 0) {
			printk("Failed to stop GPS\n");
			return -1;
		}
	}

	return 0;
}

static int init_app(void)
{
	int retval;

	if (setup_modem() != 0) {
		printk("Failed to initialize modem\n");
		return -1;
	}

	retval = gnss_ctrl(GNSS_INIT_AND_START);

	return retval;
}

static void print_satellite_stats(nrf_gnss_data_frame_t *pvt_data)
{
	uint8_t  tracked          = 0;
	uint8_t  in_fix           = 0;
	uint8_t  unhealthy        = 0;

	for (int i = 0; i < NRF_GNSS_MAX_SATELLITES; ++i) {

		if ((pvt_data->pvt.sv[i].sv > 0) &&
		    (pvt_data->pvt.sv[i].sv < 33)) {

			tracked++;
                        printk("| %.1d",pvt_data->pvt.sv[i].cn0/10);

			if (pvt_data->pvt.sv[i].flags &
					NRF_GNSS_SV_FLAG_USED_IN_FIX) {
				in_fix++;
			}

			if (pvt_data->pvt.sv[i].flags &
					NRF_GNSS_SV_FLAG_UNHEALTHY) {
				unhealthy++;
			}
		}
	}

	printk("|\nTracking: %d Using: %d Unhealthy: %d\n", tracked,
							 in_fix,
							 unhealthy);
}

static void print_gnss_stats(nrf_gnss_data_frame_t *pvt_data)
{
	if (pvt_data->pvt.flags & NRF_GNSS_PVT_FLAG_DEADLINE_MISSED) {
		printk("GNSS notification deadline missed\n");
	}
	if (pvt_data->pvt.flags & NRF_GNSS_PVT_FLAG_NOT_ENOUGH_WINDOW_TIME) {
		printk("GNSS operation blocked by insufficient time windows\n");
	}
}

static void print_fix_data(nrf_gnss_data_frame_t *pvt_data)
{
	printf("Longitude:  %f\n", pvt_data->pvt.longitude);
	printf("Latitude:   %f\n", pvt_data->pvt.latitude);
	printf("Altitude:   %f\n", pvt_data->pvt.altitude);
	printf("Speed:      %f\n", pvt_data->pvt.speed);
	printf("Heading:    %f\n", pvt_data->pvt.heading);
	printk("Date:       %02u-%02u-%02u\n", pvt_data->pvt.datetime.year,
					       pvt_data->pvt.datetime.month,
					       pvt_data->pvt.datetime.day);
	printk("Time (UTC): %02u:%02u:%02u\n", pvt_data->pvt.datetime.hour,
					       pvt_data->pvt.datetime.minute,
					      pvt_data->pvt.datetime.seconds);
}

static void print_nmea_data(void)
{
	for (int i = 0; i < nmea_string_cnt; ++i) {
		printk("%s", nmea_strings[i]);
	}
        printk("\n");
}

int process_gps_data(nrf_gnss_data_frame_t *gps_data)
{
	int retval;

	retval = nrf_recv(gnss_fd,
			  gps_data,
			  sizeof(nrf_gnss_data_frame_t),
			  NRF_MSG_DONTWAIT);

	if (retval > 0) {

		switch (gps_data->data_id) {
		case NRF_GNSS_PVT_DATA_ID:
			memcpy(&last_pvt,
			       gps_data,
			       sizeof(nrf_gnss_data_frame_t));
			nmea_string_cnt = 0;
			got_fix = false;

			if ((gps_data->pvt.flags &
				NRF_GNSS_PVT_FLAG_FIX_VALID_BIT)
				== NRF_GNSS_PVT_FLAG_FIX_VALID_BIT) {

				got_fix = true;
				fix_timestamp = k_uptime_get();
			}
			break;

		case NRF_GNSS_NMEA_DATA_ID:
			if (nmea_string_cnt < 10) {
				memcpy(nmea_strings[nmea_string_cnt++],
				       gps_data->nmea,
				       retval);
			}
			break;

		case NRF_GNSS_AGPS_DATA_ID:
#ifdef CONFIG_SUPL_CLIENT_LIB
			printk("\033[1;1H");
			printk("\033[2J");
			printk("New AGPS data requested, contacting SUPL server, flags %d\n",
			       gps_data->agps.data_flags);
			gnss_ctrl(GNSS_STOP);
			activate_lte(true);
			printk("Established LTE link\n");
			if (open_supl_socket() == 0) {
				printf("Starting SUPL session\n");
				supl_session(&gps_data->agps);
				printk("Done\n");
				close_supl_socket();
			}
			activate_lte(false);
			gnss_ctrl(GNSS_RESTART);
			k_sleep(K_MSEC(2000));
#endif
			break;

		default:
			break;
		}
	}

	return retval;
}

#ifdef CONFIG_SUPL_CLIENT_LIB
int inject_agps_type(void *agps,
		     size_t agps_size,
		     nrf_gnss_agps_data_type_t type,
		     void *user_data)
{
	ARG_UNUSED(user_data);
	int retval = nrf_sendto(gnss_fd,
				agps,
				agps_size,
				0,
				&type,
				sizeof(type));

	if (retval != 0) {
		printk("Failed to send AGNSS data, type: %d (err: %d)\n",
		       type,
		       errno);
		return -1;
	}

	printk("Injected AGPS data, flags: %d, size: %d\n", type, agps_size);

	return 0;
}
#endif

int main(void)
{
	nrf_gnss_data_frame_t gps_data;
	uint8_t		      cnt = 0;
        cellular_off = true;
#ifdef CONFIG_SUPL_CLIENT_LIB
	static struct supl_api supl_api = {
		.read       = supl_read,
		.write      = supl_write,
		.handler    = inject_agps_type,
		.logger     = supl_logger,
		.counter_ms = k_uptime_get
	};
#endif

	printk("Starting GPS application\n");

	if (init_app() != 0) {
		return -1;
	}

#ifdef CONFIG_SUPL_CLIENT_LIB
	int rc = supl_init(&supl_api);

	if (rc != 0) {
		return rc;
	}
#endif

	printk("Getting GPS data...\n");

	while (1) {

		do {
			/* Loop until we don't have more
			 * data to read
			 */
		} while (process_gps_data(&gps_data) > 0);

		if (IS_ENABLED(CONFIG_GPS_SAMPLE_NMEA_ONLY)) {
			print_nmea_data();
			nmea_string_cnt = 0;
		} else {
			printk("\033[1;1H");
			printk("\033[2J\n");
			print_satellite_stats(&last_pvt);
			print_gnss_stats(&last_pvt);
			printk("---------------------------------\n");

			if (!got_fix) {
				printk("Seconds since last fix: %lld\n",
				       (k_uptime_get() - fix_timestamp) / 1000);
				cnt++;
				printk("Searching [%c]\n",
				       update_indicator[cnt%4]);
			} else {
				print_fix_data(&last_pvt);
                                cnt++;
                                printk("%d\n",cnt);
			}
                        if (cellular_off && (cnt > 120))
                        {
                          setup_modem_xtra();
                          cellular_off = false;
                        }
			//printk("\nNMEA strings:\n\n");
			//print_nmea_data();
			printk("---------------------------------");
		}

		k_sleep(K_MSEC(500));
	}

	return 0;
}

[sjacobsen]

Looks like the multitasking is stable today, both with a CMW500 and live cellular network.  I'm using a constant SNR simulated GPS signal on a Spirent generator for consistency.   The instability I saw yesterday must have simply been the result of a poor cellular signal on a live network, although I still wonder why the at_client code exhibited no problems in the RRC idle state.

[Håkon Alseth]

Hi,

 

sjacobsen said:

Looks like the multitasking is stable today, both with a CMW500 and live cellular network.  I'm using a constant SNR simulated GPS signal on a Spirent generator for consistency.   The instability I saw yesterday must have simply been the result of a poor cellular signal on a live network, although I still wonder why the at_client code exhibited no problems in the RRC idle state.

I would recommend that you monitor the RSRP level when doing such tests. You ideally want to be at -90 dBm or higher. When you reach -100 dBm, you're near the RX sensitivity, which will mean upping the CE level (parts of your on-air payload, like preamble etc, will be retransmitted x amount of times). Such a scenario will impact timing wrt. PSM.

 

I understand that you wait 60-120 secs before enabling PSM. Straight-up delays are OK for testing scenarios, but implementations in full application should ensure that you've entered a mode where the GPS can be started without being blocked by the LTE network.

Note that most network will also have a period after requesting PSM and the UE successfully entering PSM. In my network, this is 60 seconds, but it will differ from provider-to-provider. I would recommend that you look at the AT command CSCON notification: https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/packet_domain/cscon.html?cp=2_1_6_16

 

Kind regards,

Håkon

[Chetan Kale]

Hi sjacobsen and Håkon Alseth, 

Are you able to run the GNSS and LTE concurrently? If you got this then can you share the comments how you overcome it.

Because I am able to initialize LTE and getting connected to LTE in 2-3 Sec. After that I am able to get the GPS fix and also printing the coordinates and stopping the GNSS. But if I want to get the coordinates after some time again then it throwing the error "Failed to Start GPS". 

Thank You !

Regards,

Chetan Kale