Statistics
| Branch: | Revision:

root / arduino-1.0 / libraries / Ethernet / examples / UdpNtpClient / UdpNtpClient.ino @ 58d82c77

History | View | Annotate | Download (4.17 KB)

1
/*
2

    
3
 Udp NTP Client
4
 
5
 Get the time from a Network Time Protocol (NTP) time server
6
 Demonstrates use of UDP sendPacket and ReceivePacket 
7
 For more on NTP time servers and the messages needed to communicate with them, 
8
 see http://en.wikipedia.org/wiki/Network_Time_Protocol
9
 
10
 created 4 Sep 2010 
11
 by Michael Margolis
12
 modified 17 Sep 2010
13
 by Tom Igoe
14
 
15
 This code is in the public domain.
16

    
17
 */
18

    
19
#include <SPI.h>         
20
#include <Ethernet.h>
21
#include <EthernetUdp.h>
22

    
23
// Enter a MAC address for your controller below.
24
// Newer Ethernet shields have a MAC address printed on a sticker on the shield
25
byte mac[] = {  
26
  0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
27

    
28
unsigned int localPort = 8888;      // local port to listen for UDP packets
29

    
30
IPAddress timeServer(192, 43, 244, 18); // time.nist.gov NTP server
31

    
32
const int NTP_PACKET_SIZE= 48; // NTP time stamp is in the first 48 bytes of the message
33

    
34
byte packetBuffer[ NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets 
35

    
36
// A UDP instance to let us send and receive packets over UDP
37
EthernetUDP Udp;
38

    
39
void setup() 
40
{
41
  Serial.begin(9600);
42

    
43
  // start Ethernet and UDP
44
  if (Ethernet.begin(mac) == 0) {
45
    Serial.println("Failed to configure Ethernet using DHCP");
46
    // no point in carrying on, so do nothing forevermore:
47
    for(;;)
48
      ;
49
  }
50
  Udp.begin(localPort);
51
}
52

    
53
void loop()
54
{
55
  sendNTPpacket(timeServer); // send an NTP packet to a time server
56

    
57
    // wait to see if a reply is available
58
  delay(1000);  
59
  if ( Udp.parsePacket() ) {  
60
    // We've received a packet, read the data from it
61
    Udp.read(packetBuffer,NTP_PACKET_SIZE);  // read the packet into the buffer
62

    
63
    //the timestamp starts at byte 40 of the received packet and is four bytes,
64
    // or two words, long. First, esxtract the two words:
65

    
66
    unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
67
    unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);  
68
    // combine the four bytes (two words) into a long integer
69
    // this is NTP time (seconds since Jan 1 1900):
70
    unsigned long secsSince1900 = highWord << 16 | lowWord;  
71
    Serial.print("Seconds since Jan 1 1900 = " );
72
    Serial.println(secsSince1900);               
73

    
74
    // now convert NTP time into everyday time:
75
    Serial.print("Unix time = ");
76
    // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
77
    const unsigned long seventyYears = 2208988800UL;     
78
    // subtract seventy years:
79
    unsigned long epoch = secsSince1900 - seventyYears;  
80
    // print Unix time:
81
    Serial.println(epoch);                               
82

    
83

    
84
    // print the hour, minute and second:
85
    Serial.print("The UTC time is ");       // UTC is the time at Greenwich Meridian (GMT)
86
    Serial.print((epoch  % 86400L) / 3600); // print the hour (86400 equals secs per day)
87
    Serial.print(':');  
88
    if ( ((epoch % 3600) / 60) < 10 ) {
89
      // In the first 10 minutes of each hour, we'll want a leading '0'
90
      Serial.print('0');
91
    }
92
    Serial.print((epoch  % 3600) / 60); // print the minute (3600 equals secs per minute)
93
    Serial.print(':'); 
94
    if ( (epoch % 60) < 10 ) {
95
      // In the first 10 seconds of each minute, we'll want a leading '0'
96
      Serial.print('0');
97
    }
98
    Serial.println(epoch %60); // print the second
99
  }
100
  // wait ten seconds before asking for the time again
101
  delay(10000); 
102
}
103

    
104
// send an NTP request to the time server at the given address 
105
unsigned long sendNTPpacket(IPAddress& address)
106
{
107
  // set all bytes in the buffer to 0
108
  memset(packetBuffer, 0, NTP_PACKET_SIZE); 
109
  // Initialize values needed to form NTP request
110
  // (see URL above for details on the packets)
111
  packetBuffer[0] = 0b11100011;   // LI, Version, Mode
112
  packetBuffer[1] = 0;     // Stratum, or type of clock
113
  packetBuffer[2] = 6;     // Polling Interval
114
  packetBuffer[3] = 0xEC;  // Peer Clock Precision
115
  // 8 bytes of zero for Root Delay & Root Dispersion
116
  packetBuffer[12]  = 49; 
117
  packetBuffer[13]  = 0x4E;
118
  packetBuffer[14]  = 49;
119
  packetBuffer[15]  = 52;
120

    
121
  // all NTP fields have been given values, now
122
  // you can send a packet requesting a timestamp: 		   
123
  Udp.beginPacket(address, 123); //NTP requests are to port 123
124
  Udp.write(packetBuffer,NTP_PACKET_SIZE);
125
  Udp.endPacket(); 
126
}
127

    
128

    
129

    
130

    
131

    
132

    
133

    
134

    
135

    
136