I assembled a program to synchronize my RTC DS1307.
- I start with an automatic update of the RTC: RTC.adjust(DateTime(DATE, TIME). This works fine;
- I adjust the RTC date and time to wrong values;
- I call a function Synchronize_RTC
After synchronizing the month, day, hour, minute and second are correct, but the year is 2046 in stead of 2016.
I can't find what is wrong.
/*
Udp NTP Client
Source: https://github.com/codebendercc/arduino-library-files/blob/master/libraries/Ethernet/examples/UdpNtpClient/UdpNtpClient.ino
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
Warning: NTP Servers are subject to temporary failure or IP address change.
Plese check http://tf.nist.gov/tf-cgi/servers.cgi if the time server used in the example didn't work.
Created 4 Sep 2010 by Michael Margolis
Modified 9 Apr 2012 by Tom Igoe
Modified 25 March 2016 C.W.A. Baltus
Hardware:
- Arduino Mega 2560 Rev.3
- Ethernet Shield W5100
- RTC DS1307
Software:
- Version 1.6.1
*/
//================================================================================================
//Libraries
#include <Wire.h> //Enables I2C communication
#include <RTClib.h>
#include <SPI.h>
#include <Ethernet.h>
#include <EthernetUdp.h>
RTC_DS1307 RTC;
// 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(129, 6, 15, 28);
//IPAddress timeServer(132, 163, 4, 101); // time-a.timefreq.bldrdoc.gov NTP server //OKE 20160324
//IPAddress timeServer(132, 163, 4, 102); // time-b.timefreq.bldrdoc.gov NTP server //OKE 20160324
//IPAddress timeServer(132, 163, 4, 103); // time-c.timefreq.bldrdoc.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() {
Serial.begin(9600); // Open serial communications and wait for port to open:
Wire.begin();
RTC.begin();
if (! RTC.isrunning()) {
Serial.println("RTC is NOT running!");
// Synchronizing the RTC to the (date & time) of the PC
RTC.adjust(DateTime(__DATE__, __TIME__));
}
RTC.adjust(DateTime(__DATE__, __TIME__));
DateTime now = RTC.now();
Serial.print("Time after automatic update: ");
Serial.print(now.year(), DEC); Serial.print("-"); Serial.print(now.month(),DEC); Serial.print("-"); Serial.print(now.day(), DEC); Serial.print(" ");
Serial.print (now.hour(), DEC); Serial.print(":"); Serial.print(now.minute(), DEC); Serial.print(":"); Serial.println (now.second(), DEC);
// start Ethernet and UDP
if (Ethernet.begin(mac) == 0)
{Serial.println("Failed to configure Ethernet using DHCP"); }
else
{Serial.println("Ethernet connection succesfuill");}
Udp.begin(localPort);
//Set manually a wrong time
RTC.adjust(DateTime(2015,6,21,9,51,05));
now = RTC.now();
Serial.print ("Wrong time: ");
Serial.print(now.year()); Serial.print("-"); Serial.print(now.month(),DEC); Serial.print("-"); Serial.print(now.day(), DEC); Serial.print(" ");
Serial.print (now.hour(), DEC); Serial.print(":"); Serial.print(now.minute(), DEC); Serial.print(":"); Serial.println (now.second(), DEC);
//Synchronize the RTC with NTP
Synchronize_RTC();
now = RTC.now();
Serial.print ("Corrected time with NTP: ");
Serial.print(now.year()); Serial.print("-"); Serial.print(now.month(),DEC); Serial.print("-"); Serial.print(now.day(), DEC); Serial.print(" ");
Serial.print (now.hour(), DEC); Serial.print(":"); Serial.print(now.minute(), DEC); Serial.print(":"); Serial.println (now.second(), DEC);
}
//==========================================================================
void loop(){
}
//==========================================================================
unsigned long sendNTPpacket(IPAddress& address)
// send an NTP request to the time server at the given 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();
} //End sendNTPpacket
//============================================================================
void Synchronize_RTC()
{
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:
// 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 | packetBuffer[16+i];
t2 = t2 << 8 | packetBuffer[24+i];
t3 = t3 << 8 | packetBuffer[32+i];
t4 = t4 << 8 | packetBuffer[40+i];}
//Serial.print(t1); Serial.print(" "); Serial.print(t2); Serial.print(" ");Serial.print(t3); Serial.print(" ");Serial.println(t4);
// 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)packetBuffer[20] * 256 + packetBuffer[21]) / 65536.0;
f2 = ((long)packetBuffer[28] * 256 + packetBuffer[29]) / 65536.0;
f3 = ((long)packetBuffer[36] * 256 + packetBuffer[37]) / 65536.0;
f4 = ((long)packetBuffer[44] * 256 + packetBuffer[45]) / 65536.0;
const unsigned long seventyYears = 2208988800UL;
//const unsigned long seventyYears =0UL;
t1 -= seventyYears;
t2 -= seventyYears;
t3 -= seventyYears;
t4 -= seventyYears;
// Adjust timezone and DST... in my case substract 4 hours for Chile Time or work in UTC?
t4 += (2 * 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));
} //End ParsePcket
} //End function Synchronize_RTC
and the NTP is not stable.