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151 lines
4.7 KiB
C++
151 lines
4.7 KiB
C++
/*
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Udp NTP Client
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Get the time from a Network Time Protocol (NTP) time server
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Demonstrates use of UDP sendPacket and ReceivePacket
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For more on NTP time servers and the messages needed to communicate with them,
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see http://en.wikipedia.org/wiki/Network_Time_Protocol
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Warning: NTP Servers are subject to temporary failure or IP address change.
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Plese check
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http://tf.nist.gov/tf-cgi/servers.cgi
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if the time server used in the example didn't work.
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created 4 Sep 2010
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by Michael Margolis
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modified 9 Apr 2012
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by Tom Igoe
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This code is in the public domain.
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*/
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#include <SPI.h>
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#include <Ethernet.h>
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#include <EthernetUdp.h>
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// Enter a MAC address for your controller below.
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// Newer Ethernet shields have a MAC address printed on a sticker on the shield
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byte mac[] = {
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0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
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unsigned int localPort = 8888; // local port to listen for UDP packets
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IPAddress timeServer(132, 163, 4, 101); // time-a.timefreq.bldrdoc.gov NTP server
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// IPAddress timeServer(132, 163, 4, 102); // time-b.timefreq.bldrdoc.gov NTP server
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// IPAddress timeServer(132, 163, 4, 103); // time-c.timefreq.bldrdoc.gov NTP server
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const int NTP_PACKET_SIZE= 48; // NTP time stamp is in the first 48 bytes of the message
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byte packetBuffer[ NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets
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// A UDP instance to let us send and receive packets over UDP
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EthernetUDP Udp;
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void setup()
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{
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// Open serial communications and wait for port to open:
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Serial.begin(9600);
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while (!Serial) {
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; // wait for serial port to connect. Needed for Leonardo only
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}
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// start Ethernet and UDP
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if (Ethernet.begin(mac) == 0) {
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Serial.println("Failed to configure Ethernet using DHCP");
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// no point in carrying on, so do nothing forevermore:
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for(;;)
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;
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}
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Udp.begin(localPort);
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}
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void loop()
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{
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sendNTPpacket(timeServer); // send an NTP packet to a time server
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// wait to see if a reply is available
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delay(1000);
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if ( Udp.parsePacket() ) {
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// We've received a packet, read the data from it
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Udp.read(packetBuffer,NTP_PACKET_SIZE); // read the packet into the buffer
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//the timestamp starts at byte 40 of the received packet and is four bytes,
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// or two words, long. First, esxtract the two words:
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unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
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unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);
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// combine the four bytes (two words) into a long integer
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// this is NTP time (seconds since Jan 1 1900):
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unsigned long secsSince1900 = highWord << 16 | lowWord;
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Serial.print("Seconds since Jan 1 1900 = " );
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Serial.println(secsSince1900);
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// now convert NTP time into everyday time:
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Serial.print("Unix time = ");
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// Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
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const unsigned long seventyYears = 2208988800UL;
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// subtract seventy years:
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unsigned long epoch = secsSince1900 - seventyYears;
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// print Unix time:
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Serial.println(epoch);
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// print the hour, minute and second:
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Serial.print("The UTC time is "); // UTC is the time at Greenwich Meridian (GMT)
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Serial.print((epoch % 86400L) / 3600); // print the hour (86400 equals secs per day)
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Serial.print(':');
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if ( ((epoch % 3600) / 60) < 10 ) {
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// In the first 10 minutes of each hour, we'll want a leading '0'
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Serial.print('0');
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}
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Serial.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute)
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Serial.print(':');
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if ( (epoch % 60) < 10 ) {
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// In the first 10 seconds of each minute, we'll want a leading '0'
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Serial.print('0');
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}
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Serial.println(epoch %60); // print the second
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}
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// wait ten seconds before asking for the time again
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delay(10000);
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}
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// send an NTP request to the time server at the given address
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unsigned long sendNTPpacket(IPAddress& address)
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{
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// set all bytes in the buffer to 0
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memset(packetBuffer, 0, NTP_PACKET_SIZE);
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// Initialize values needed to form NTP request
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// (see URL above for details on the packets)
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packetBuffer[0] = 0b11100011; // LI, Version, Mode
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packetBuffer[1] = 0; // Stratum, or type of clock
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packetBuffer[2] = 6; // Polling Interval
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packetBuffer[3] = 0xEC; // Peer Clock Precision
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// 8 bytes of zero for Root Delay & Root Dispersion
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packetBuffer[12] = 49;
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packetBuffer[13] = 0x4E;
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packetBuffer[14] = 49;
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packetBuffer[15] = 52;
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// all NTP fields have been given values, now
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// you can send a packet requesting a timestamp:
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Udp.beginPacket(address, 123); //NTP requests are to port 123
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Udp.write(packetBuffer,NTP_PACKET_SIZE);
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Udp.endPacket();
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}
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