add time sync via sntp

main/CMakeLists.txt

@@ -1,2 +1,2 @@
-idf_component_register(SRCS "main.c" "tic.c" "wifi.c" "mqtt.c" "libteleinfo.cpp" "libteleinfo/src/LibTeleinfo.cpp"
+idf_component_register(SRCS "main.c" "tic.c" "wifi.c" "mqtt.c" "sntp.c" "libteleinfo.cpp" "libteleinfo/src/LibTeleinfo.cpp"
                     INCLUDE_DIRS ".")

main/main.c

@@ -12,6 +12,7 @@
 #include "tic.h"
 #include "wifi.h"
 #include "mqtt.h"
+#include "sntp.h"
 
 // Embedded via component.mk
 extern const uint8_t cacert_pem_start[]   asm("_binary_cacert_pem_start");
@@ -28,6 +29,8 @@ void app_main(void) {
     wifi_init_sta();
     wifi_wait_for_online();
     mqtt_init();
+    sntp_start();
     mqtt_wait_for_readiness();
+    sntp_wait_for_readiness();
     tic_uart_init();
 }

main/sntp.c

@@ -0,0 +1,68 @@
+#include <string.h>
+#include <time.h>
+#include <sys/time.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "freertos/event_groups.h"
+#include "esp_system.h"
+#include "esp_event.h"
+#include "esp_log.h"
+#include "esp_attr.h"
+#include "esp_sntp.h"
+#include "sntp.h"
+
+/* FreeRTOS event group to signal when we are connected*/
+static EventGroupHandle_t s_sntp_event_group;
+
+/* The event group allows multiple bits for each event, but we only care about one event:
+ * - time is synchronized
+ */
+#define TIME_SYNC_BIT BIT0
+
+static const char *SNTP_LOGGER = "sntp";
+
+void sntp_callback(struct timeval *tv) {
+    if (sntp_get_sync_mode() == SNTP_SYNC_MODE_IMMED) {
+        time_t now;
+        time(&now);
+        struct tm now_tm;
+        localtime_r(&now, &now_tm);
+        char strftime_buf[64];
+        if (strftime(strftime_buf, sizeof(strftime_buf), "%c", &now_tm)) {
+            ESP_LOGI(SNTP_LOGGER, "Time synchronized: %s", strftime_buf);
+        }
+        sntp_set_sync_mode(SNTP_SYNC_MODE_SMOOTH);
+        xEventGroupSetBits(s_sntp_event_group, TIME_SYNC_BIT);
+    }
+}
+
+void sntp_start() {
+    s_sntp_event_group = xEventGroupCreate();
+    ESP_LOGI(SNTP_LOGGER, "Initializing SNTP...");
+    sntp_setoperatingmode(SNTP_OPMODE_POLL);
+    sntp_setservername(0, "pool.ntp.org");
+    sntp_set_time_sync_notification_cb(sntp_callback);
+    sntp_set_sync_mode(SNTP_SYNC_MODE_IMMED);
+    sntp_init();
+}
+
+void sntp_wait_for_readiness(void) {
+    /* Waiting until the connection is established (MQTT_CONNECTED_BIT).
+     * The bits are set by mqtt_event_handler_cb() (see above)
+     */
+    EventBits_t bits = xEventGroupWaitBits(s_sntp_event_group,
+            TIME_SYNC_BIT,
+            pdFALSE,
+            pdFALSE,
+            portMAX_DELAY);
+
+    /* xEventGroupWaitBits() returns the bits before the call returned, hence we can test which event actually
+     * happened. */
+    if (bits & TIME_SYNC_BIT) {
+        ESP_LOGI(SNTP_LOGGER, "Time is synchronized!");
+    } else {
+        ESP_LOGE(SNTP_LOGGER, "UNEXPECTED EVENT");
+    }
+
+    //vEventGroupDelete(s_sntp_event_group);
+}

main/sntp.h

@@ -0,0 +1,7 @@
+#ifndef __SNTP_H__
+#define __SNTP_H__
+
+void sntp_start();
+void sntp_wait_for_readiness(void);
+
+#endif