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+/*
+
+ Udp NTP Client
+
+ Get the time from a Network Time Protocol (NTP) time server
+ Demonstrates use of UDP sendPacket and ReceivePacket
+ For more on NTP time servers and the messages needed to communicate with them,
+ see http://en.wikipedia.org/wiki/Network_Time_Protocol
+
+ created 4 Sep 2010
+ by Michael Margolis
+ modified 9 Apr 2012
+ by Tom Igoe
+
+ This code is in the public domain.
+
+ */
+
+#include <SPI.h>
+#include <Ethernet.h>
+#include <EthernetUdp.h>
+
+// Enter a MAC address for your controller below.
+// Newer Ethernet shields have a MAC address printed on a sticker on the shield
+byte mac[] = {
+ 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
+
+unsigned int localPort = 8888; // local port to listen for UDP packets
+
+IPAddress timeServer(192, 43, 244, 18); // time.nist.gov NTP server
+
+const int NTP_PACKET_SIZE= 48; // NTP time stamp is in the first 48 bytes of the message
+
+byte packetBuffer[ NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets
+
+// A UDP instance to let us send and receive packets over UDP
+EthernetUDP Udp;
+
+void setup()
+{
+ // Open serial communications and wait for port to open:
+ Serial.begin(9600);
+ while (!Serial) {
+ ; // wait for serial port to connect. Needed for Leonardo only
+ }
+
+
+ // start Ethernet and UDP
+ if (Ethernet.begin(mac) == 0) {
+ Serial.println("Failed to configure Ethernet using DHCP");
+ // no point in carrying on, so do nothing forevermore:
+ for(;;)
+ ;
+ }
+ Udp.begin(localPort);
+}
+
+void loop()
+{
+ sendNTPpacket(timeServer); // send an NTP packet to a time server
+
+ // wait to see if a reply is available
+ delay(1000);
+ if ( Udp.parsePacket() ) {
+ // We've received a packet, read the data from it
+ Udp.read(packetBuffer,NTP_PACKET_SIZE); // read the packet into the buffer
+
+ //the timestamp starts at byte 40 of the received packet and is four bytes,
+ // or two words, long. First, esxtract the two words:
+
+ unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
+ unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);
+ // combine the four bytes (two words) into a long integer
+ // this is NTP time (seconds since Jan 1 1900):
+ unsigned long secsSince1900 = highWord << 16 | lowWord;
+ Serial.print("Seconds since Jan 1 1900 = " );
+ Serial.println(secsSince1900);
+
+ // now convert NTP time into everyday time:
+ Serial.print("Unix time = ");
+ // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
+ const unsigned long seventyYears = 2208988800UL;
+ // subtract seventy years:
+ unsigned long epoch = secsSince1900 - seventyYears;
+ // print Unix time:
+ Serial.println(epoch);
+
+
+ // print the hour, minute and second:
+ Serial.print("The UTC time is "); // UTC is the time at Greenwich Meridian (GMT)
+ Serial.print((epoch % 86400L) / 3600); // print the hour (86400 equals secs per day)
+ Serial.print(':');
+ if ( ((epoch % 3600) / 60) < 10 ) {
+ // In the first 10 minutes of each hour, we'll want a leading '0'
+ Serial.print('0');
+ }
+ Serial.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute)
+ Serial.print(':');
+ if ( (epoch % 60) < 10 ) {
+ // In the first 10 seconds of each minute, we'll want a leading '0'
+ Serial.print('0');
+ }
+ Serial.println(epoch %60); // print the second
+ }
+ // wait ten seconds before asking for the time again
+ delay(10000);
+}
+
+// send an NTP request to the time server at the given address
+unsigned long sendNTPpacket(IPAddress& address)
+{
+ // set all bytes in the buffer to 0
+ memset(packetBuffer, 0, NTP_PACKET_SIZE);
+ // Initialize values needed to form NTP request
+ // (see URL above for details on the packets)
+ packetBuffer[0] = 0b11100011; // LI, Version, Mode
+ packetBuffer[1] = 0; // Stratum, or type of clock
+ packetBuffer[2] = 6; // Polling Interval
+ packetBuffer[3] = 0xEC; // Peer Clock Precision
+ // 8 bytes of zero for Root Delay & Root Dispersion
+ packetBuffer[12] = 49;
+ packetBuffer[13] = 0x4E;
+ packetBuffer[14] = 49;
+ packetBuffer[15] = 52;
+
+ // all NTP fields have been given values, now
+ // you can send a packet requesting a timestamp:
+ Udp.beginPacket(address, 123); //NTP requests are to port 123
+ Udp.write(packetBuffer,NTP_PACKET_SIZE);
+ Udp.endPacket();
+}
+
+
+
+
+
+
+
+
+
+