arduino-0022

arduino-0022-linux-x64/libraries/Ethernet/examples/UdpNtpClient/UdpNtpClient.pde

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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 17 Sep 2010
+ by Tom Igoe
+ 
+ This code is in the public domain.
+
+ */
+
+#include <SPI.h>         
+#include <Ethernet.h>
+#include <Udp.h>
+
+// Enter a MAC address and IP address for your controller below.
+// The IP address will be dependent on your local network:
+byte mac[] = {  
+  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
+byte ip[] = { 
+  192,168,1,177 };
+
+
+unsigned int localPort = 8888;      // local port to listen for UDP packets
+
+byte 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 
+
+void setup() 
+{
+  // start Ethernet and UDP
+  Ethernet.begin(mac,ip);
+  Udp.begin(localPort);
+
+  Serial.begin(9600);
+}
+
+void loop()
+{
+  sendNTPpacket(timeServer); // send an NTP packet to a time server
+
+    // wait to see if a reply is available
+  delay(1000);  
+  if ( Udp.available() ) {  
+    Udp.readPacket(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(':');  
+    Serial.print((epoch  % 3600) / 60); // print the minute (3600 equals secs per minute)
+    Serial.print(':'); 
+    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(byte *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.sendPacket( packetBuffer,NTP_PACKET_SIZE,  address, 123); //NTP requests are to port 123
+}
+
+
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