View source for Arduino: LCD Clock NTP Sync




 //sample code originated at http://www.openreefs.com/ntpServer
 //modified by Steve Spence, http://arduinotronics.blogspot.com
 
 #include <SPI.h>
 #include <Ethernet.h>
 #include <EthernetUdp.h>
 #include <Time.h>
 #include <LiquidCrystal.h>

 /* ******** Ethernet Card Settings ******** */
 // Set this to your Ethernet Card Mac Address
 byte mac[] = { 0x90, 0xA2, 0xDA, 0x00, 0x23, 0x36 };
 
 /* ******** NTP Server Settings ******** */
 /* us.pool.ntp.org NTP server
    (Set to your time server of choice) */
 IPAddress timeServer(202, 65, 114, 202);
 
 /* Set this to the offset (in seconds) to your local time
    This example is GMT +7 */
 const long timeZoneOffset = 25200L; 
 
 /* Syncs to NTP server every 15 seconds for testing,
    set to 1 hour or more to be reasonable */
 unsigned int ntpSyncTime = 3600;       
 
 
 /* ALTER THESE VARIABLES AT YOUR OWN RISK */
 // local port to listen for UDP packets
 unsigned int localPort = 8888;
 // NTP time stamp is in the first 48 bytes of the message
 const int NTP_PACKET_SIZE= 48;     
 // Buffer to hold incoming and outgoing packets
 byte packetBuffer[NTP_PACKET_SIZE]; 
 // A UDP instance to let us send and receive packets over UDP
 EthernetUDP Udp;                   
 // Keeps track of how long ago we updated the NTP server
 unsigned long ntpLastUpdate = 0;   
 // Check last time clock displayed (Not in Production)
 time_t prevDisplay = 0;           
 
 void setup() {
    Serial.begin(9600);
   
    // Ethernet shield and NTP setup
    int i = 0;
    int DHCP = 0;
    DHCP = Ethernet.begin(mac);
    //Try to get dhcp settings 30 times before giving up
    while( DHCP == 0 && i < 30){
      delay(1000);
      DHCP = Ethernet.begin(mac);
      i++;
    }
    if(!DHCP){
     Serial.println("DHCP FAILED");
      for(;;); //Infinite loop because DHCP Failed
    }
    Serial.println("DHCP Success");
   
    //Try to get the date and time
    int trys=0;
    while(!getTimeAndDate() && trys<10) {
      trys++;
    }
 } 
 
 // Do not alter this function, it is used by the system
 int getTimeAndDate() {
    int flag=0;
    Udp.begin(localPort);
    sendNTPpacket(timeServer);
    delay(1000);
    if (Udp.parsePacket()){
      Udp.read(packetBuffer,NTP_PACKET_SIZE);  // read the packet into the buffer
      unsigned long highWord, lowWord, epoch;
      highWord = word(packetBuffer[40], packetBuffer[41]);
      lowWord = word(packetBuffer[42], packetBuffer[43]); 
      epoch = highWord << 16 | lowWord;
      epoch = epoch - 2208988800 + timeZoneOffset;
      flag=1;
      setTime(epoch);
      ntpLastUpdate = now();
    }
    return flag;
 }

 // Do not alter this function, it is used by the system
 unsigned long sendNTPpacket(IPAddress& address)
 {
   memset(packetBuffer, 0, NTP_PACKET_SIZE);
   packetBuffer[0] = 0b11100011;
   packetBuffer[1] = 0;
   packetBuffer[2] = 6;
   packetBuffer[3] = 0xEC;
   packetBuffer[12]  = 49;
   packetBuffer[13]  = 0x4E;
   packetBuffer[14]  = 49;
   packetBuffer[15]  = 52;                 
   Udp.beginPacket(address, 123);
   Udp.write(packetBuffer,NTP_PACKET_SIZE);
   Udp.endPacket();
 }
 
 void displaytime()
 {
   LiquidCrystal lcd(12,11,5,4,3,2);
   lcd.setCursor(0,0);
   if (hour() < 10) lcd.print ("0");
   lcd.print (hour());
   lcd.print (":");
   if (minute() < 10) lcd.print ("0");
   lcd.print (minute());
   lcd.print (":");
   if (second() < 10) lcd.print ("0");
   lcd.print (second());
   lcd.print (" ");  
 
   return;  
 }
 
 // Clock display of the time and date (Basic)
 void clockDisplay(){
   Serial.print(hour());
   printDigits(minute());
   printDigits(second());
   Serial.print(" ");
   Serial.print(day());
   Serial.print(" ");
   Serial.print(month());
   Serial.print(" ");
   Serial.print(year());
   Serial.println();
 }
 
 // Utility function for clock display: prints preceding colon and leading 0
 void printDigits(int digits){
   Serial.print(":");
   if(digits < 10)
     Serial.print('0');
   Serial.print(digits);
 }
 
 // This is where all the magic happens...
 void loop() {
     // Update the time via NTP server as often as the time you set at the top
     if(now()-ntpLastUpdate > ntpSyncTime) {
       int trys=0;
       while(!getTimeAndDate() && trys<10){
         trys++;
       }
       if(trys<10){
         Serial.println("ntp server update success");
       }
       else{
         Serial.println("ntp server update failed");
       }
     }
   
     // Display the time if it has changed by more than a second.
     if( now() != prevDisplay){
       prevDisplay = now();
       clockDisplay();
       displaytime();
     }
 }