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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 "YAHMS_SyncTime.h"
#include <Flash.h>
#ifdef LOGGING
FLASH_STRING(SECONDS_SINCE_1900,"Seconds since Jan 1 1900 = ");
FLASH_STRING(UNIX_TIME,"Unix time = ");
#endif
#define LOCALPORT 8888
//unsigned int localPort = 8888; // local port to listen for UDP packets
IPAddress timeServer(91,189,94,4); // time.ubuntu.com NTP server
#define NTP_PACKET_SIZE 48
//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 SyncTime_setup()
{
Udp.begin(LOCALPORT);
setSyncProvider(getNtpTime);
while(timeStatus()== timeNotSet)
; // wait until the time is set by the sync provider
}
unsigned long getNtpTime()
{
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;
#ifdef LOGGING
Serial.print("Seconds since Jan 1 1900 = " );
Serial.println(secsSince1900);
#endif
// now convert NTP time into everyday 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:
#ifdef LOGGING
Serial.print(UNIX_TIME);
Serial.println(epoch);
#endif
return epoch;
}
return 0; // return 0 if unable to get the time
}
// 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();
}