NTP 網路校時

#include <TimeLib.h>

#include <WiFiUdp.h>

char ntpServerName[] = "us.pool.ntp.org";

int timeZone = 0;

WiFiUDP Udp;

unsigned int localPort = 8888;

time_t getNtpTime();

int digitalClockDisplay(char d);

void printDigits(int digits);

void sendNTPpacket(IPAddress &address);

int digitalClockDisplay(char m){

int interm;

if (m=='h'){

interm=hour();

return interm;

}

if (m=='m'){

interm=minute();

return interm;

}

if (m=='s'){

interm=second();

return interm;

}

if (m=='w'){

interm=weekday();

return interm;

}

if (m=='j'){

interm=day();

return interm;

}

if (m=='n'){

interm=month();

return interm;

}

if (m=='y'){

interm=year();

return interm;

}

}

 /*-------- NTP code ----------*/

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

byte packetBuffer[NTP_PACKET_SIZE]; //buffer to hold incoming & outgoing packets

time_t getNtpTime()

{

IPAddress ntpServerIP; // NTP server's ip address

while (Udp.parsePacket() > 0) ; // discard any previously received packets

Serial.println("Transmit NTP Request");

// get a random server from the pool

WiFi.hostByName(ntpServerName, ntpServerIP);

Serial.print(ntpServerName);

Serial.print(":");

Serial.println(ntpServerIP);

sendNTPpacket(ntpServerIP);

uint32_t beginWait = millis();

while (millis() - beginWait < 1500) {

int size = Udp.parsePacket();

if (size >= NTP_PACKET_SIZE) {

Serial.println("Receive NTP Response");

Udp.read(packetBuffer, NTP_PACKET_SIZE);  // read packet into the buffer

unsigned long secsSince1900;

// convert four bytes starting at location 40 to a long integer

secsSince1900 =  (unsigned long)packetBuffer[40] << 24;

secsSince1900 |= (unsigned long)packetBuffer[41] << 16;

secsSince1900 |= (unsigned long)packetBuffer[42] << 8;

secsSince1900 |= (unsigned long)packetBuffer[43];

return secsSince1900 - 2208988800UL + timeZone * SECS_PER_HOUR;

}

}

Serial.println("No NTP Response :-(");

return 0; // return 0 if unable to get the time

}

void sendNTPpacket(IPAddress &address)

{

memset(packetBuffer, 0, NTP_PACKET_SIZE);

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

packetBuffer[12] = 49;

packetBuffer[13] = 0x4E;

packetBuffer[14] = 49;

packetBuffer[15] = 52;

Udp.beginPacket(address, 123); //NTP requests are to port 123

Udp.write(packetBuffer, NTP_PACKET_SIZE);

Udp.endPacket();

}

==============================================

setup(){

......

Udp.begin(localPort);

setSyncProvider(getNtpTime);

setSyncInterval(300);

}

==============================================

loop(){

......

digitalClockDisplay('s');

}