feat: enable BLE CTS service

This patch enables ZephyrWatch to communicate with a BLE client using
Current Time Service GATT and update its global unix time. Please find
the client implementation in the following repo:

- updatetime.py in github.com/electricalgorithm/ZephyrWatchBLETools

Author: electricalgorithm

src/bluetooth/services/current_time_service.c

@@ -3,6 +3,7 @@
 #include <zephyr/bluetooth/gatt.h>
 #include <string.h>
 
+#include "current_time_service.h"
 #include "timeutils/timeutils.h"
 #include "devicetwin/devicetwin.h"
 
@@ -27,22 +28,26 @@ static ssize_t m_time_write_callback(
 	uint32_t unix_timestamp = sys_le32_to_cpu(*(uint32_t *)buf);
 	LOG_INF("Received UNIX timestamp: %u", unix_timestamp);
 
-	// Convert UNIX timestamp to UTC time
-	utc_time_t utc_time = unix_to_utc(unix_timestamp);
-	
-	// Get the device twin instance
+	// Get the device twin instance to get the UTC zone
 	device_twin_t *device_twin = get_device_twin_instance();
 	if (device_twin == NULL) {
 		LOG_ERR("Failed to get device twin instance.");
 		return BT_GATT_ERR(BT_ATT_ERR_UNLIKELY);
 	}
 
-	// Update the device twin's current time
-	device_twin->current_time = utc_time;
+	// Convert UNIX timestamp to local time using the device's UTC zone
+	utc_time_t local_time = unix_to_localtime(unix_timestamp, device_twin->utc_zone);
+
+	// Update the device twin's current time with local time
+	device_twin->current_time = local_time;
 
-	LOG_INF("Current time updated: %04d-%02d-%02d %02d:%02d:%02d", 
-		utc_time.year, utc_time.month, utc_time.day,
-		utc_time.hour, utc_time.minute, utc_time.second);
+	// Update the global unix time used by the UI system
+	update_global_unix_time(unix_timestamp);
+
+	LOG_INF("Current time updated to local time: %04d-%02d-%02d %02d:%02d:%02d (UTC%+d)", 
+		local_time.year, local_time.month, local_time.day,
+		local_time.hour, local_time.minute, local_time.second,
+		device_twin->utc_zone);
 
 	return len;
 }

src/bluetooth/services/current_time_service.h

@@ -0,0 +1,20 @@
+#ifndef CURRENT_TIME_SERVICE_H
+#define CURRENT_TIME_SERVICE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <zephyr/sys/byteorder.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/bluetooth/gatt.h>
+#include "timeutils/timeutils.h"
+
+/* Function to update the global unix time - to be implemented in main.c */
+extern void update_global_unix_time(uint32_t unix_timestamp);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // CURRENT_TIME_SERVICE_H

src/display/screens/home/home.c

@@ -74,7 +74,7 @@ uint8_t home_screen_set_date(uint16_t year, uint8_t month, uint8_t day) {
     // Check if the label_date is NULL.
     if (label_date == NULL) return 1;
     // Set the text of the label_date to the current date in "YYYY-MM-DD" format.
-    lv_label_set_text_fmt(label_date, "%04u-%02d-%02d", year,  month + 1, day);
+    lv_label_set_text_fmt(label_date, "%04u-%02d-%02d", year,  month, day);
     // Update the display.
     lv_disp_flush_ready(lv_disp_get_default());
     return 0;

src/main.c

@@ -25,13 +25,14 @@
 #include "timeutils/timeutils.h"
 #include "devicetwin/devicetwin.h"
 #include "bluetooth/infrastructure.h"
+#include "bluetooth/services/current_time_service.h"
 
 // Define the logger.
 LOG_MODULE_REGISTER(ZephyrWatch, LOG_LEVEL_DBG);
 
 // Global values to hold time.
 uint32_t unix_time = 1748554674;
-int8_t utc_zone = +1;
+int8_t utc_zone = +2;
 const char* weekdays[] = { "SUN", "MON", "TUE", "WED", "THU", "FRI", "SAT" };
 
 // Define the timer callbacks' prototypes.
@@ -161,6 +162,25 @@ void update_unix_time_callback(struct k_timer *timer) {
 	unix_time += 1;
 }
 
+/* UPDATE_GLOBAL_UNIX_TIME
+ * Function to update the global unix time from external sources
+ * (like Bluetooth CTS). This function will be called by the external
+ * sources.
+ */
+void update_global_unix_time(uint32_t unix_timestamp) {
+    unix_time = unix_timestamp;
+    LOG_INF("Global UNIX time updated to: %u", unix_time);
+
+    // Only submit if not already pending.
+    if (!k_work_is_pending(&clock_update_work)) {
+        k_work_submit_to_queue(&ui_work_q, &clock_update_work);
+    }
+    if (!k_work_is_pending(&date_day_update_work)) {
+        k_work_submit_to_queue(&ui_work_q, &date_day_update_work);
+    }
+}
+
+
 /* CLOCK_UPDATE_WORKER
  * This function is called by the UI work queue to update the clock view.
  * It updates the current time in the device twin and then
@@ -174,7 +194,7 @@ void clock_update_worker(struct k_work *work) {
     utc_time_t local_time = unix_to_localtime(unix_time, device_twin->utc_zone);
     device_twin->current_time = local_time;
 
-    // Update the clock view.
+    // Update the clock view using the device twin's current time.
     uint8_t ret = home_screen_set_clock(device_twin->current_time.hour, device_twin->current_time.minute);
     if (ret != 0) {
         LOG_ERR("Failed to update the clock view.");
@@ -194,12 +214,12 @@ void date_day_update_worker(struct k_work *work) {
     utc_time_t local_time = unix_to_localtime(unix_time, device_twin->utc_zone);
     device_twin->current_time = local_time;
 
-    // Update the date and day views.
-    uint8_t ret = home_screen_set_date(local_time.year, local_time.month, local_time.day);
+    // Update the date and day views using the device twin's current time.
+    uint8_t ret = home_screen_set_date(device_twin->current_time.year, device_twin->current_time.month, device_twin->current_time.day);
     if (ret != 0) {
         LOG_ERR("Failed to update the date view.");
     }
-    ret = home_screen_set_day(weekdays[local_time.weekday]);
+    ret = home_screen_set_day(weekdays[device_twin->current_time.weekday]);
     if (ret != 0) {
         LOG_ERR("Failed to update the day view.");
     }