Hi guys,
I have a problem with NTP sync.
T1 .. T4 && fractional parts
2045-08-02 00:14:16 0.4545
2066-02-06 06:28:16 0.0000
2045-08-02 00:14:23 0.4436
2045-08-02 00:14:23 0.4437
/*
* NAME: NTP2RTC
* DATE: 2012-02-19
* URL: http://playground.arduino.cc/Main/DS1307OfTheLogshieldByMeansOfNTP
*
* PURPOSE:
* Get the time from a Network Time Protocol (NTP) time server
* and store it to the RTC of the adafruit logshield
*
* NTP is described in:
* http://www.ietf.org/rfc/rfc958.txt (obsolete)
* http://www.ietf.org/rfc/rfc5905.txt
*
* based upon Udp NTP Client, by Michael Margolis, mod by Tom Igoe
* uses the RTClib from adafruit (based upon Jeelabs)
* Thanx!
* mod by Rob Tillaart, 10-10-2010
*
* This code is in the public domain.
*
*/
// libraries for ethershield
#include <SPI.h>
#include <Ethernet.h>
#if ARDUINO >= 100
#include <EthernetUdp.h> // New from IDE 1.0
#else
#include <Udp.h>
#endif
// libraries for realtime clock
#include <Wire.h>
#include <RTClib.h>
RTC_DS1307 rtc;
// Enter a MAC address and IP address for your controller below.
// The IP address will be dependent on your local network:
byte mac[] = { 0x00, 0x11, 0x22, 0x33, 0xFB, 0x11 }; // Use your MAC address
byte ip[] = { 192, 168, 0, 1 }; // no DHCP so we set our own IP address
byte subnet[] = { 255, 255, 255, 0 }; // subnet mask
byte gateway[] = { 192, 168, 0, 2 }; // internet access via router
unsigned int localPort = 8888; // local port to listen for UDP packets
// find your local ntp server http://www.pool.ntp.org/zone/europe or
// http://support.ntp.org/bin/view/Servers/StratumTwoTimeServers
// byte timeServer[] = {192, 43, 244, 18}; // time.nist.gov NTP server
byte timeServer[] = {193, 79, 237, 14}; // ntp1.nl.net NTP server
const int NTP_PACKET_SIZE= 48; // NTP time stamp is in the first 48 bytes of the message
byte pb[NTP_PACKET_SIZE]; // buffer to hold incoming and outgoing packets
#if ARDUINO >= 100
// An EthernetUDP instance to let us send and receive packets over UDP
EthernetUDP Udp; // New from IDE 1.0
#endif
///////////////////////////////////////////
//
// SETUP
//
void setup()
{
Serial.begin(19200);
Serial.println("NTP2RTC 0.5");
// start Ethernet and UDP
Ethernet.begin(mac); // For when you are directly connected to the Internet.
Udp.begin(localPort);
Serial.println("network ...");
// init RTC
Wire.begin();
rtc.begin();
Serial.println("rtc ...");
Serial.println();
}
///////////////////////////////////////////
//
// LOOP
//
void loop()
{
Serial.print("RTC before: ");
PrintDateTime(rtc.now());
Serial.println();
// send an NTP packet to a time server
sendNTPpacket(timeServer);
// wait to see if a reply is available
delay(1000);
if ( Udp.parsePacket() ) {
// read the packet into the buffer
#if ARDUINO >= 100
Udp.read(pb, NTP_PACKET_SIZE); // New from IDE 1.0,
#else
Udp.readPacket(pb, NTP_PACKET_SIZE);
#endif
// NTP contains four timestamps with an integer part and a fraction part
// we only use the integer part here
unsigned long t1, t2, t3, t4;
t1 = t2 = t3 = t4 = 0;
for (int i=0; i< 4; i++)
{
t1 = t1 << 8 | pb[16+i];
t2 = t2 << 8 | pb[24+i];
t3 = t3 << 8 | pb[32+i];
t4 = t4 << 8 | pb[40+i];
}
// part of the fractional part
// could be 4 bytes but this is more precise than the 1307 RTC
// which has a precision of ONE second
// in fact one byte is sufficient for 1307
float f1,f2,f3,f4;
f1 = ((long)pb[20] * 256 + pb[21]) / 65536.0;
f2 = ((long)pb[28] * 256 + pb[29]) / 65536.0;
f3 = ((long)pb[36] * 256 + pb[37]) / 65536.0;
f4 = ((long)pb[44] * 256 + pb[45]) / 65536.0;
// NOTE:
// one could use the fractional part to set the RTC more precise
// 1) at the right (calculated) moment to the NEXT second!
// t4++;
// delay(1000 - f4*1000);
// RTC.adjust(DateTime(t4));
// keep in mind that the time in the packet was the time at
// the NTP server at sending time so one should take into account
// the network latency (try ping!) and the processing of the data
// ==> delay (850 - f4*1000);
// 2) simply use it to round up the second
// f > 0.5 => add 1 to the second before adjusting the RTC
// (or lower threshold eg 0.4 if one keeps network latency etc in mind)
// 3) a SW RTC might be more precise, => ardomic clock :)
// convert NTP to UNIX time, differs seventy years = 2208988800 seconds
// NTP starts Jan 1, 1900
// Unix time starts on Jan 1 1970.
const unsigned long seventyYears = 2208988800UL;
t1 -= seventyYears;
t2 -= seventyYears;
t3 -= seventyYears;
t4 -= seventyYears;
Serial.println("T1 .. T4 && fractional parts");
PrintDateTime(DateTime(t1)); Serial.println(f1,4);
PrintDateTime(DateTime(t2)); Serial.println(f2,4);
PrintDateTime(DateTime(t3)); Serial.println(f3,4);
PrintDateTime(DateTime(t4)); Serial.println(f4,4);
Serial.println();
// Adjust timezone and DST... in my case substract 4 hours for Chile Time
// or work in UTC?
t4 -= (3 * 3600L); // Notice the L for long calculations!!
t4 += 1; // adjust the delay(1000) at begin of loop!
if (f4 > 0.4) t4++; // adjust fractional part, see above
rtc.adjust(DateTime(t4));
Serial.print("RTC after : ");
PrintDateTime(rtc.now());
Serial.println();
Serial.println("done ...");
// endless loop
while(1);
}
else
{
Serial.println("No UDP available ...");
}
// wait 1 minute before asking for the time again
// you don't want to annoy NTP server admin's
delay(60000L);
}
///////////////////////////////////////////
//
// MISC
//
void PrintDateTime(DateTime t)
{
char datestr[24];
sprintf(datestr, "%04d-%02d-%02d %02d:%02d:%02d ", t.year(), t.month(), t.day(), t.hour(), t.minute(), t.second());
Serial.print(datestr);
}
// 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(pb, 0, NTP_PACKET_SIZE);
// Initialize values needed to form NTP request
// (see URL above for details on the packets)
pb[0] = 0b11100011; // LI, Version, Mode
pb[1] = 0; // Stratum, or type of clock
pb[2] = 6; // Polling Interval
pb[3] = 0xEC; // Peer Clock Precision
// 8 bytes of zero for Root Delay & Root Dispersion
pb[12] = 49;
pb[13] = 0x4E;
pb[14] = 49;
pb[15] = 52;
// all NTP fields have been given values, now
// you can send a packet requesting a timestamp:
#if ARDUINO >= 100
// IDE 1.0 compatible:
Udp.beginPacket(address, 123); //NTP requests are to port 123
Udp.write(pb,NTP_PACKET_SIZE);
Udp.endPacket();
#else
Udp.sendPacket( pb,NTP_PACKET_SIZE, address, 123); //NTP requests are to port 123
#endif
}
///////////////////////////////////////////
//
// End of program
//
Any Ideas
The Time is OK, but the date is wrong, 30 years in the future 
The original code has not been modified, and belongs to Rod.
My board is an Arduino DUE with Ethernet Shield and Tiny RTC 1307
Best Regards.