Fix of NTP logic. Minor refactoring.

include/wordclock_esp8266.h

@@ -2,6 +2,7 @@
 #define WORDCLOCK_ESP8266_H
 
 #include <Arduino.h>
+#include <stdlib.h> 
 #include <ESP8266WebServer.h>
 #include "led_matrix.h"
 #include "udp_logger.h"
@@ -11,6 +12,13 @@
 
 #define EEPROM_SIZE (sizeof(EepromLayout_st) / sizeof(uint8_t))
 
+#define BUILD_YEAR (__DATE__ + 7)                  /* Will expand to current year at compile time as string. */
+#define NTP_MININUM_RX_YEAR (atoi(BUILD_YEAR) - 1) /* Will expand to current year at compile time minus one. */
+#define NTP_MININUM_YEAR (1900)                    // NTP minimum year is 1900
+#define NTP_MAX_UPDATE_TIME_US (500000)    // 500ms max update time
+#define NTP_NEXT_UPDATE_DELAY_US (10000000)        // 10s delay time between updates
+#define NTP_WATCHDOG_COUNTER_INIT (30)             // Watchdog value, count of retries before restart
+
 typedef struct
 {
     int start_hour;
@@ -54,6 +62,7 @@ typedef enum
     NUM_STATES
 } ClockState_en;
 
+bool get_ntp_time(uint32 usec);
 String leading_zero2digit(int value);
 uint8_t calculate_dynamic_brightness(uint8_t min_brightness, uint8_t max_brightness, int hours, int minutes, bool summertime);
 uint8_t update_brightness(void);
@@ -67,8 +76,7 @@ void handle_data_request(void);
 void handle_led_direct(void);
 void limit_value_ranges(void);
 void log_time(tm local_time);
-void ntp_time_update(uint32 *last_ntp_update_us);
-void ntp_time_update(uint32 *last_ntp_update_us);
+void ntp_time_update(uint32 max_update_time);
 void on_state_entry(uint8_t state);
 void read_settings_from_EEPROM(void);
 void reset_wifi_credentials(void);