feat(modem): Support for pausing network in C-API

also adds a demo of this feature to pppos client example

components/esp_modem/examples/pppos_client/main/Kconfig.projbuild

@@ -201,4 +201,14 @@ menu "Example Configuration"
         help
             MQTT data message, which we publish and expect to receive.
 
+    config EXAMPLE_PAUSE_NETIF_TO_CHECK_SIGNAL
+        bool "Demonstrate netif pause"
+        default n
+        help
+            Set this to true to demonstrate network pausing.
+            If enabled, the example waits for an MQTT data, then temporarily
+            drops network to check signal quality, resumes networking and
+            publishes another MQTT message.
+            Connection to the MQTT broker should be kept.
+
 endmenu

components/esp_modem/examples/pppos_client/main/pppos_client_main.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Unlicense OR CC0-1.0
  */
@@ -317,6 +317,20 @@ void app_main(void)
     esp_mqtt_client_handle_t mqtt_client = esp_mqtt_client_init(&mqtt_config);
     esp_mqtt_client_register_event(mqtt_client, ESP_EVENT_ANY_ID, mqtt_event_handler, NULL);
     esp_mqtt_client_start(mqtt_client);
+
+#if CONFIG_EXAMPLE_PAUSE_NETIF_TO_CHECK_SIGNAL
+    xEventGroupWaitBits(event_group, GOT_DATA_BIT, pdTRUE, pdFALSE, portMAX_DELAY);
+    esp_modem_pause_net(dce, true);
+    err = esp_modem_get_signal_quality(dce, &rssi, &ber);
+    if (err != ESP_OK) {
+        ESP_LOGE(TAG, "esp_modem_get_signal_quality failed with %d", err);
+        return;
+    }
+    ESP_LOGI(TAG, "Signal quality: rssi=%d, ber=%d", rssi, ber);
+    esp_modem_pause_net(dce, false);
+    esp_mqtt_client_publish(mqtt_client, CONFIG_EXAMPLE_MQTT_TEST_TOPIC, CONFIG_EXAMPLE_MQTT_TEST_DATA, 0, 0, 0);
+#endif
+
     ESP_LOGI(TAG, "Waiting for MQTT data");
     xEventGroupWaitBits(event_group, GOT_DATA_BIT | USB_DISCONNECTED_BIT, pdFALSE, pdFALSE, portMAX_DELAY);
     CHECK_USB_DISCONNECTION(event_group);

components/esp_modem/examples/pppos_client/sdkconfig.ci.sim800_c3

@@ -11,5 +11,6 @@ CONFIG_EXAMPLE_MODEM_DEVICE_SIM800=y
 CONFIG_EXAMPLE_MODEM_DEVICE_BG96=n
 CONFIG_EXAMPLE_MODEM_PPP_APN="lpwa.vodafone.com"
 CONFIG_EXAMPLE_MQTT_TEST_TOPIC="/ci/esp-modem/pppos-client"
+CONFIG_EXAMPLE_PAUSE_NETIF_TO_CHECK_SIGNAL=y
 CONFIG_ESP_SYSTEM_PANIC_PRINT_HALT=y
 CONFIG_ESP32_PANIC_PRINT_HALT=y

components/esp_modem/include/esp_modem_c_api_types.h

@@ -160,6 +160,17 @@ esp_err_t esp_modem_set_apn(esp_modem_dce_t *dce, const char *apn);
 esp_err_t esp_modem_set_urc(esp_modem_dce_t *dce, esp_err_t(*got_line_cb)(uint8_t *data, size_t len));
 #endif
 
+/**
+ * @brief This API provides support for temporarily pausing networking in order
+ * to send/receive AT commands and resume networking afterwards.
+ * @note This function does not switch modes, the modem is still in data mode.
+ *
+ * @param dce Modem DCE handle
+ * @param pause true to pause the network interface, false to resume networking
+ * @return ESP_OK on success
+ */
+esp_err_t esp_modem_pause_net(esp_modem_dce_t *dce, bool pause);
+
 /**
  * @}
  */

components/esp_modem/src/esp_modem_c_api.cpp

@@ -475,3 +475,11 @@ extern "C" esp_err_t esp_modem_set_urc(esp_modem_dce_t *dce_wrap, esp_err_t(*got
     return ESP_OK;
 }
 #endif
+
+extern "C" esp_err_t esp_modem_pause_net(esp_modem_dce_t *dce_wrap, bool pause)
+{
+    if (dce_wrap == nullptr || dce_wrap->dce == nullptr) {
+        return ESP_ERR_INVALID_ARG;
+    }
+    return command_response_to_esp_err(dce_wrap->dce->pause_netif(pause));
+}