Arduino: RTC DS1302 NTP Sync

// time ntp RTC DS1302 set

1. include <Time.h>
2. include <SPI.h>
3. include <Ethernet.h>
4. include <EthernetUdp.h>
5. include <DS1302.h>

// Init the DS1302 // DS1302 rtc([CE/RST], [I/O], [CLOCK]); DS1302 rtc(8, 7, 6);

// Ethernet library configuration byte mac[] = { 0x24, 0x7B, 0xA2, 0x4A, 0x52, 0x10 }; IPAddress timeServer(128, 138, 140, 44 ); // time.nist.gov

unsigned int localPort = 8888; const int NTP_PACKET_SIZE= 48; byte packetBuffer[NTP_PACKET_SIZE]; EthernetUDP Udp;

void setup() {

 // Set the clock to run-mode, and disable the write protection
 rtc.halt(false);
 rtc.writeProtect(false);

 // Setup Communication
 Serial.begin(9600);
 Ethernet.begin(mac);
 Udp.begin(localPort);

 Serial.print("get time");
 setSyncInterval(10); // Set seconds between re-sync
 getNtpTime;

 // The following lines can be commented out to use the values already stored in the DS1302
 rtc.setDOW(WEDNESDAY);        // Set Day-of-Week to MONDAY
 // rtc.setTime(13, 0, 0);     // Set the time to 12:00:00 (24hr format)
 rtc.setDate(30, 5, 2018);   // Set the date to Feb 2, 2016

}

void loop() {

 setSyncProvider(getNtpTime);

 rtc.setTime(hour()+7, minute(), second());

 // Send Day-of-Week
 Serial.print(rtc.getDOWStr());
 Serial.print(" ");
 
 // Send date
 Serial.print(rtc.getDateStr());
 Serial.print(" -- ");

 // Send time
 Serial.println(rtc.getTimeStr());
 
 getNtpTime;
 // delay(1000);

}

/*-------- NTP code ----------*/

unsigned long getNtpTime() {

 sendNTPpacket(timeServer); // send an NTP packet to a time server
   delay(500);
  
   if ( Udp.parsePacket() ) {
    Udp.read(packetBuffer,NTP_PACKET_SIZE);
    unsigned long hi = word(packetBuffer[40], packetBuffer[41]);
    unsigned long low = word(packetBuffer[42], packetBuffer[43]);
    unsigned long secsSince1900 = hi << 16 | low; 
    const unsigned long seventyYears = 2208988800UL;     
    unsigned long epoch = secsSince1900 - seventyYears;
    return epoch;
 }
 return 0; // return 0 if unable to get the time

}

unsigned long sendNTPpacket(IPAddress& address) {

 memset(packetBuffer, 0, NTP_PACKET_SIZE);  // set all bytes in the buffer to 0

 // Initialize values needed to form NTP request
 packetBuffer[0] = B11100011;   // LI, Version, Mode
 packetBuffer[1] = 0;     // Stratum
 packetBuffer[2] = 6;     // Max Interval between messages in seconds
 packetBuffer[3] = 0xEC;  // Clock Precision
 // bytes 4 - 11 are for Root Delay and Dispersion and were set to 0 by memset
 packetBuffer[12]  = 49;  // four-byte reference ID identifying
 packetBuffer[13]  = 0x4E;
 packetBuffer[14]  = 49;
 packetBuffer[15]  = 52;

 // send the packet requesting a timestamp:
 Udp.beginPacket(address, 123); //NTP requests are to port 123
 Udp.write(packetBuffer,NTP_PACKET_SIZE);
 Udp.endPacket();

}