conn_mgr and LTE-M PSM

[thijsfranssen]

Hi, 

I really like the new Zephyr conn_mgr, it is really easy to use, almost UNIX like. I am wondering what is now the best way to control PSM. Will CONFIG_LTE_LINK_CONTROL and lte_lc_connect_async interfere with the conn_mgr? Should I only use one of the options or can they exist next to each other? 

will CONN_MGR_IF_NO_AUTO_CONNECT and then connection using lte_lc work reliable?

I am searching for the "right" way to do. 

Thanks!

[Michal]

Hello,

I will have to look more into conn_mgr, but I am not sure if our LTE code is well-integrated with that feature.

To be safe I would recommend using our LTE link control library.

Best regards,

Michal

[thijsfranssen]

Looks like conn_mgr and LTE Link control can (or even needs to) work next to each other. I can image someone else is also struggling wit it so this is how I got it to work, it is actually quite easy.

Add this to prj.conf:

##Custom
CONFIG_LTE_LINK_CONTROL=y
## PSM
CONFIG_LTE_PSM_REQ_RPTAU="01010100"
CONFIG_LTE_PSM_REQ_RAT="00000001"

Then copy and edit the LTE_Handler from the example just above the main function. I changed to LOG_INF instead of printk and added te PSM part.

static void lte_handler(const struct lte_lc_evt *const evt)
{
        switch (evt->type) {
        case LTE_LC_EVT_NW_REG_STATUS:
                if (evt->nw_reg_status != LTE_LC_NW_REG_REGISTERED_HOME &&
                    evt->nw_reg_status != LTE_LC_NW_REG_REGISTERED_ROAMING) {
                        break;
                }

                LOG_INF("Connected to: %s network\n",
                       evt->nw_reg_status == LTE_LC_NW_REG_REGISTERED_HOME ? "home" : "roaming");

                break;

		case LTE_LC_EVT_PSM_UPDATE:
			LOG_INF("PSM parameter update: TAU: %d, Active time: %d\n", evt->psm_cfg.tau,
				evt->psm_cfg.active_time);
			//activeTime = evt->psm_cfg.active_time;
			//tauTime = evt->psm_cfg.tau;
			break;
        case LTE_LC_EVT_EDRX_UPDATE:
        case LTE_LC_EVT_RRC_UPDATE:
        case LTE_LC_EVT_CELL_UPDATE:
        case LTE_LC_EVT_LTE_MODE_UPDATE:
        case LTE_LC_EVT_TAU_PRE_WARNING:
        case LTE_LC_EVT_NEIGHBOR_CELL_MEAS:
        case LTE_LC_EVT_MODEM_SLEEP_EXIT_PRE_WARNING:
        case LTE_LC_EVT_MODEM_SLEEP_EXIT:
        case LTE_LC_EVT_MODEM_SLEEP_ENTER:
        case LTE_LC_EVT_MODEM_EVENT:
                /* Handle LTE events */
                break;

        default:
                break;
        }
}

Then in main add this before connecting to the network.

	lte_lc_register_handler(lte_handler);

And add this after connection is established.

	err = lte_lc_psm_req(true);
	if (err) {
		LOG_ERR("Requesting PSM failed, error: %d\n", err);
	}  	

If PSM request went alright you will see this in the serial log:

:03.150,970] <inf> aws_iot_sample: Network connectivity established
[00:00:03.151,550] <inf> aws_iot_sample: PSM parameter update: TAU: 756000, Active time: 16

And you can clearly see the 16s active time using the PPK, After 16 the power consumption will go down. I have't optimized it in this case. 

Complete AWS example main.c

/*
 * Copyright (c) 2020 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

#include <zephyr/kernel.h>
#include <zephyr/sys/reboot.h>
#include <zephyr/dfu/mcuboot.h>
#include <zephyr/logging/log.h>
#include <zephyr/logging/log_ctrl.h>
#include <zephyr/net/conn_mgr_connectivity.h>
#include <zephyr/net/conn_mgr_monitor.h>
#include <net/aws_iot.h>
#include <stdio.h>
#include <stdlib.h>
#include <hw_id.h>
#include <modem/modem_info.h>
#include <modem/lte_lc.h>


#include "json_payload.h"

/* Register log module */
LOG_MODULE_REGISTER(aws_iot_sample, CONFIG_AWS_IOT_SAMPLE_LOG_LEVEL);

/* Macros used to subscribe to specific Zephyr NET management events. */
#define L4_EVENT_MASK (NET_EVENT_L4_CONNECTED | NET_EVENT_L4_DISCONNECTED)
#define CONN_LAYER_EVENT_MASK (NET_EVENT_CONN_IF_FATAL_ERROR)

#define MODEM_FIRMWARE_VERSION_SIZE_MAX 50

/* Macro called upon a fatal error, reboots the device. */
#define FATAL_ERROR()					\
	LOG_ERR("Fatal error! Rebooting the device.");	\
	LOG_PANIC();					\
	IF_ENABLED(CONFIG_REBOOT, (sys_reboot(0)))

/* Zephyr NET management event callback structures. */
static struct net_mgmt_event_callback l4_cb;
static struct net_mgmt_event_callback conn_cb;

/* Forward declarations. */
static void shadow_update_work_fn(struct k_work *work);
static void connect_work_fn(struct k_work *work);
static void aws_iot_event_handler(const struct aws_iot_evt *const evt);

/* Work items used to control some aspects of the sample. */
static K_WORK_DELAYABLE_DEFINE(shadow_update_work, shadow_update_work_fn);
static K_WORK_DELAYABLE_DEFINE(connect_work, connect_work_fn);

/* Static functions */

static int app_topics_subscribe(void)
{
	int err;
	static const char custom_topic[] = "my-custom-topic/example";

	const struct aws_iot_topic_data topics_list[CONFIG_AWS_IOT_APP_SUBSCRIPTION_LIST_COUNT] = {
		[0].str = custom_topic,
		[0].len = strlen(custom_topic),

	};

	err = aws_iot_subscription_topics_add(topics_list, ARRAY_SIZE(topics_list));
	if (err) {
		LOG_ERR("aws_iot_subscription_topics_add, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	return 0;
}

static int aws_iot_client_init(void)
{
	int err;
	struct aws_iot_config config = { 0 };

#if defined(CONFIG_AWS_IOT_SAMPLE_DEVICE_ID_USE_HW_ID)
	char device_id[HW_ID_LEN] = { 0 };

	/* Get unique hardware ID, can be used as AWS IoT MQTT broker device/client ID. */
	err = hw_id_get(device_id, ARRAY_SIZE(device_id));
	if (err) {
		LOG_ERR("Failed to retrieve device ID, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	/* To use HW ID as MQTT device/client ID set the CONFIG_AWS_IOT_CLIENT_ID_APP option.
	 * Otherwise the ID set by CONFIG_AWS_IOT_CLIENT_ID_STATIC is used.
	 */
	config.client_id = device_id;
	config.client_id_len = strlen(device_id);

	LOG_INF("Hardware ID: %s", device_id);
#endif /* CONFIG_AWS_IOT_SAMPLE_DEVICE_ID_USE_HW_ID */

	err = aws_iot_init(&config, aws_iot_event_handler);
	if (err) {
		LOG_ERR("AWS IoT library could not be initialized, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	/* Add application specific non-shadow topics to the AWS IoT library.
	 * These topics will be subscribed to when connecting to the broker.
	 */
	err = app_topics_subscribe();
	if (err) {
		LOG_ERR("Adding application specific topics failed, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	return 0;
}

/* System Workqueue handlers. */

static void shadow_update_work_fn(struct k_work *work)
{
	int err;
	char message[CONFIG_AWS_IOT_SAMPLE_JSON_MESSAGE_SIZE_MAX] = { 0 };
	struct payload payload = {
		.state.reported.uptime = k_uptime_get(),
		.state.reported.app_version = CONFIG_AWS_IOT_SAMPLE_APP_VERSION,
	};
	struct aws_iot_data tx_data = {
		.qos = MQTT_QOS_0_AT_MOST_ONCE,
		.topic.type = AWS_IOT_SHADOW_TOPIC_UPDATE,
	};

	if (IS_ENABLED(CONFIG_MODEM_INFO)) {
		char modem_version_temp[MODEM_FIRMWARE_VERSION_SIZE_MAX];

		err = modem_info_get_fw_version(modem_version_temp,
						ARRAY_SIZE(modem_version_temp));
		if (err) {
			LOG_ERR("modem_info_get_fw_version, error: %d", err);
			FATAL_ERROR();
			return;
		}

		payload.state.reported.modem_version = modem_version_temp;
	}

	err = json_payload_construct(message, sizeof(message), &payload);
	if (err) {
		LOG_ERR("json_payload_construct, error: %d", err);
		FATAL_ERROR();
		return;
	}

	tx_data.ptr = message;
	tx_data.len = strlen(message);

	LOG_INF("Publishing message: %s to AWS IoT shadow", message);

	err = aws_iot_send(&tx_data);
	if (err) {
		LOG_ERR("aws_iot_send, error: %d", err);
		FATAL_ERROR();
		return;
	}

	(void)k_work_reschedule(&shadow_update_work,
				K_SECONDS(120));
}

static void connect_work_fn(struct k_work *work)
{
	int err;

	LOG_INF("Connecting to AWS IoT");

	err = aws_iot_connect(NULL);
	if (err) {
		LOG_ERR("aws_iot_connect, error: %d", err);
	}

	LOG_INF("Next connection retry in %d seconds",
		CONFIG_AWS_IOT_SAMPLE_CONNECTION_RETRY_TIMEOUT_SECONDS);

	(void)k_work_reschedule(&connect_work,
				K_SECONDS(CONFIG_AWS_IOT_SAMPLE_CONNECTION_RETRY_TIMEOUT_SECONDS));
}

/* Functions that are executed on specific connection-related events. */

static void on_aws_iot_evt_connected(const struct aws_iot_evt *const evt)
{
	(void)k_work_cancel_delayable(&connect_work);

	/* If persistent session is enabled, the AWS IoT library will not subscribe to any topics.
	 * Topics from the last session will be used.
	 */
	if (evt->data.persistent_session) {
		LOG_WRN("Persistent session is enabled, using subscriptions "
			"from the previous session");
	}

	/* Mark image as working to avoid reverting to the former image after a reboot. */
#if defined(CONFIG_BOOTLOADER_MCUBOOT)
	boot_write_img_confirmed();
#endif

	/* Start sequential updates to AWS IoT. */
	(void)k_work_reschedule(&shadow_update_work, K_NO_WAIT);
}

static void on_aws_iot_evt_disconnected(void)
{
	(void)k_work_cancel_delayable(&shadow_update_work);
	(void)k_work_reschedule(&connect_work, K_SECONDS(5));
}

static void on_aws_iot_evt_fota_done(const struct aws_iot_evt *const evt)
{
	int err;

	/* Tear down MQTT connection. */
	(void)aws_iot_disconnect();
	(void)k_work_cancel_delayable(&connect_work);

	/* If modem FOTA has been carried out, the modem needs to be reinitialized.
	 * This is carried out by bringing the network interface down/up.
	 */
	if (evt->data.image & DFU_TARGET_IMAGE_TYPE_ANY_MODEM) {
		LOG_INF("Modem FOTA done, reinitializing the modem");

		err = conn_mgr_all_if_down(true);
		if (err) {
			LOG_ERR("conn_mgr_all_if_down, error: %d", err);
			FATAL_ERROR();
			return;
		}

		err = conn_mgr_all_if_up(true);
		if (err) {
			LOG_ERR("conn_mgr_all_if_up, error: %d", err);
			FATAL_ERROR();
			return;
		}

	} else if (evt->data.image & DFU_TARGET_IMAGE_TYPE_ANY_APPLICATION) {
		LOG_INF("Application FOTA done, rebooting");
		IF_ENABLED(CONFIG_REBOOT, (sys_reboot(0)));
	} else {
		LOG_WRN("Unexpected FOTA image type");
	}
}

static void on_net_event_l4_connected(void)
{
	(void)k_work_reschedule(&connect_work, K_SECONDS(5));
}

static void on_net_event_l4_disconnected(void)
{
	(void)aws_iot_disconnect();
	(void)k_work_cancel_delayable(&connect_work);
	(void)k_work_cancel_delayable(&shadow_update_work);
}

/* Event handlers */

static void aws_iot_event_handler(const struct aws_iot_evt *const evt)
{
	switch (evt->type) {
	case AWS_IOT_EVT_CONNECTING:
		LOG_INF("AWS_IOT_EVT_CONNECTING");
		break;
	case AWS_IOT_EVT_CONNECTED:
		LOG_INF("AWS_IOT_EVT_CONNECTED");
		on_aws_iot_evt_connected(evt);
		break;
	case AWS_IOT_EVT_READY:
		LOG_INF("AWS_IOT_EVT_READY");
		break;
	case AWS_IOT_EVT_DISCONNECTED:
		LOG_INF("AWS_IOT_EVT_DISCONNECTED");
		on_aws_iot_evt_disconnected();
		break;
	case AWS_IOT_EVT_DATA_RECEIVED:
		LOG_INF("AWS_IOT_EVT_DATA_RECEIVED");

		LOG_INF("Received message: \"%.*s\" on topic: \"%.*s\"", evt->data.msg.len,
									 evt->data.msg.ptr,
									 evt->data.msg.topic.len,
									 evt->data.msg.topic.str);
		break;
	case AWS_IOT_EVT_PUBACK:
		LOG_INF("AWS_IOT_EVT_PUBACK, message ID: %d", evt->data.message_id);
		break;
	case AWS_IOT_EVT_PINGRESP:
		LOG_INF("AWS_IOT_EVT_PINGRESP");
		break;
	case AWS_IOT_EVT_FOTA_START:
		LOG_INF("AWS_IOT_EVT_FOTA_START");
		break;
	case AWS_IOT_EVT_FOTA_ERASE_PENDING:
		LOG_INF("AWS_IOT_EVT_FOTA_ERASE_PENDING");
		break;
	case AWS_IOT_EVT_FOTA_ERASE_DONE:
		LOG_INF("AWS_FOTA_EVT_ERASE_DONE");
		break;
	case AWS_IOT_EVT_FOTA_DONE:
		LOG_INF("AWS_IOT_EVT_FOTA_DONE");
		on_aws_iot_evt_fota_done(evt);
		break;
	case AWS_IOT_EVT_FOTA_DL_PROGRESS:
		LOG_INF("AWS_IOT_EVT_FOTA_DL_PROGRESS, (%d%%)", evt->data.fota_progress);
		break;
	case AWS_IOT_EVT_ERROR:
		LOG_INF("AWS_IOT_EVT_ERROR, %d", evt->data.err);
		break;
	case AWS_IOT_EVT_FOTA_ERROR:
		LOG_INF("AWS_IOT_EVT_FOTA_ERROR");
		break;
	default:
		LOG_WRN("Unknown AWS IoT event type: %d", evt->type);
		break;
	}
}

static void l4_event_handler(struct net_mgmt_event_callback *cb,
			     uint32_t event,
			     struct net_if *iface)
{
	switch (event) {
	case NET_EVENT_L4_CONNECTED:
		LOG_INF("Network connectivity established");
		on_net_event_l4_connected();
		break;
	case NET_EVENT_L4_DISCONNECTED:
		LOG_INF("Network connectivity lost");
		on_net_event_l4_disconnected();
		break;
	default:
		/* Don't care */
		return;
	}
}

static void connectivity_event_handler(struct net_mgmt_event_callback *cb,
				       uint32_t event,
				       struct net_if *iface)
{
	if (event == NET_EVENT_CONN_IF_FATAL_ERROR) {
		LOG_ERR("NET_EVENT_CONN_IF_FATAL_ERROR");
		FATAL_ERROR();
		return;
	}
}

static void lte_handler(const struct lte_lc_evt *const evt)
{
        switch (evt->type) {
        case LTE_LC_EVT_NW_REG_STATUS:
                if (evt->nw_reg_status != LTE_LC_NW_REG_REGISTERED_HOME &&
                    evt->nw_reg_status != LTE_LC_NW_REG_REGISTERED_ROAMING) {
                        break;
                }

                LOG_INF("Connected to: %s network\n",
                       evt->nw_reg_status == LTE_LC_NW_REG_REGISTERED_HOME ? "home" : "roaming");

                break;

		case LTE_LC_EVT_PSM_UPDATE:
			LOG_INF("PSM parameter update: TAU: %d, Active time: %d\n", evt->psm_cfg.tau,
				evt->psm_cfg.active_time);
			//activeTime = evt->psm_cfg.active_time;
			//tauTime = evt->psm_cfg.tau;
			break;
        case LTE_LC_EVT_EDRX_UPDATE:
        case LTE_LC_EVT_RRC_UPDATE:
        case LTE_LC_EVT_CELL_UPDATE:
        case LTE_LC_EVT_LTE_MODE_UPDATE:
        case LTE_LC_EVT_TAU_PRE_WARNING:
        case LTE_LC_EVT_NEIGHBOR_CELL_MEAS:
        case LTE_LC_EVT_MODEM_SLEEP_EXIT_PRE_WARNING:
        case LTE_LC_EVT_MODEM_SLEEP_EXIT:
        case LTE_LC_EVT_MODEM_SLEEP_ENTER:
        case LTE_LC_EVT_MODEM_EVENT:
                /* Handle LTE events */
                break;

        default:
                break;
        }
}

int main(void)
{
	LOG_INF("The AWS IoT sample started, version: %s", CONFIG_AWS_IOT_SAMPLE_APP_VERSION);

	int err;

	/* Setup handler for Zephyr NET Connection Manager events. */
	net_mgmt_init_event_callback(&l4_cb, l4_event_handler, L4_EVENT_MASK);
	net_mgmt_add_event_callback(&l4_cb);

	/* Setup handler for Zephyr NET Connection Manager Connectivity layer. */
	net_mgmt_init_event_callback(&conn_cb, connectivity_event_handler, CONN_LAYER_EVENT_MASK);
	net_mgmt_add_event_callback(&conn_cb);

	lte_lc_register_handler(lte_handler);

	/* Connecting to the configured connectivity layer.
	 * Wi-Fi or LTE depending on the board that the sample was built for.
	 */
	LOG_INF("Bringing network interface up and connecting to the network");

	err = conn_mgr_all_if_up(true);
	if (err) {
		LOG_ERR("conn_mgr_all_if_up, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	err = lte_lc_psm_req(true);
	if (err) {
		LOG_ERR("Requesting PSM failed, error: %d\n", err);
	}  	

	err = aws_iot_client_init();
	if (err) {
		LOG_ERR("aws_iot_client_init, error: %d", err);
		FATAL_ERROR();
		return err;
	}

	err = lte_lc_psm_req(true);
	if (err) {
		LOG_ERR("Requesting PSM failed, error: %d\n", err);
	}  

	return 0;
}

[Michal]

That's a nice writeup!

Thank you for sharing that, it may be helpful to other people as well.

Best regards,

Michal

[mahabib]

Thank you for the write-up. Just a heads up I had the same issue, the -14 (-EFAULT) err code is due to AT command failing in nrf_modem_lib.c. This can be resolved via a call to nrf_modem_lib_init(), before calling lte_lc_init_and_connect_async(), this way the example works with out PSM or conn_mgr. 

[Sage_Duggal]

I just wanted to respond and say thank you for the write up. This helped me a lot. I ended up doing the PSM request in my prj.conf file, and then implemented lte_lc_psm_get() at run-time. Thanks again!