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Arduino/libraries/WiFi/examples/WiFiUdpNtpClient/WiFiUdpNtpClient.ino

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/*
Udp NTP Client
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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,
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see http://en.wikipedia.org/wiki/Network_Time_Protocol
created 4 Sep 2010
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by Michael Margolis
modified 9 Apr 2012
by Tom Igoe
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This code is in the public domain.
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*/
#include <SPI.h>
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#include <WiFi.h>
#include <WiFiUdp.h>
int status = WL_IDLE_STATUS;
char ssid[] = "mynetwork"; // your network SSID (name)
char pass[] = "mypassword"; // your network password
int keyIndex = 0; // your network key Index number (needed only for WEP)
unsigned int localPort = 2390; // local port to listen for UDP packets
IPAddress timeServer(129, 6, 15, 28); // time.nist.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
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// A UDP instance to let us send and receive packets over UDP
WiFiUDP Udp;
void setup() {
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// Open serial communications and wait for port to open:
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for native USB port only
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}
// check for the presence of the shield:
if (WiFi.status() == WL_NO_SHIELD) {
Serial.println("WiFi shield not present");
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// don't continue:
while (true);
}
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String fv = WiFi.firmwareVersion();
if (fv != "1.1.0") {
Serial.println("Please upgrade the firmware");
}
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// attempt to connect to Wifi network:
while (status != WL_CONNECTED) {
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Serial.print("Attempting to connect to SSID: ");
Serial.println(ssid);
// Connect to WPA/WPA2 network. Change this line if using open or WEP network:
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status = WiFi.begin(ssid, pass);
// wait 10 seconds for connection:
delay(10000);
}
Serial.println("Connected to wifi");
printWifiStatus();
Serial.println("\nStarting connection to server...");
Udp.begin(localPort);
}
void loop() {
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sendNTPpacket(timeServer); // send an NTP packet to a time server
// wait to see if a reply is available
delay(1000);
if (Udp.parsePacket()) {
Serial.println("packet received");
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// We've received a packet, read the data from it
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,
// 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]);
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// 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;
Serial.print("Seconds since Jan 1 1900 = ");
Serial.println(secsSince1900);
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// now convert NTP time into everyday time:
Serial.print("Unix time = ");
// Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
const unsigned long seventyYears = 2208988800UL;
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// subtract seventy years:
unsigned long epoch = secsSince1900 - seventyYears;
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// print Unix time:
Serial.println(epoch);
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// print the hour, minute and second:
Serial.print("The UTC time is "); // UTC is the time at Greenwich Meridian (GMT)
Serial.print((epoch % 86400L) / 3600); // print the hour (86400 equals secs per day)
Serial.print(':');
if (((epoch % 3600) / 60) < 10) {
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// In the first 10 minutes of each hour, we'll want a leading '0'
Serial.print('0');
}
Serial.print((epoch % 3600) / 60); // print the minute (3600 equals secs per minute)
Serial.print(':');
if ((epoch % 60) < 10) {
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// In the first 10 seconds of each minute, we'll want a leading '0'
Serial.print('0');
}
Serial.println(epoch % 60); // print the second
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}
// wait ten seconds before asking for the time again
delay(10000);
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}
// send an NTP request to the time server at the given address
unsigned long sendNTPpacket(IPAddress& address) {
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//Serial.println("1");
// set all bytes in the buffer to 0
memset(packetBuffer, 0, NTP_PACKET_SIZE);
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// Initialize values needed to form NTP request
// (see URL above for details on the packets)
//Serial.println("2");
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;
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packetBuffer[13] = 0x4E;
packetBuffer[14] = 49;
packetBuffer[15] = 52;
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//Serial.println("3");
// all NTP fields have been given values, now
// you can send a packet requesting a timestamp:
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Udp.beginPacket(address, 123); //NTP requests are to port 123
//Serial.println("4");
Udp.write(packetBuffer, NTP_PACKET_SIZE);
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//Serial.println("5");
Udp.endPacket();
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//Serial.println("6");
}
void printWifiStatus() {
// print the SSID of the network you're attached to:
Serial.print("SSID: ");
Serial.println(WiFi.SSID());
// print your WiFi shield's IP address:
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");
Serial.println(ip);
// print the received signal strength:
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.print(rssi);
Serial.println(" dBm");
}