watt_time.cpp

#include <ESP8266WiFi.h>        //https://github.com/esp8266/Arduino
#include <WiFiUdp.h>            //Arduino library
#include "watt_time.h"

// NTP Servers:
static const char ntpServerName[] = NTP_SERVER;
// Set Time Zone
const int timeZone = TIME_ZONE;
// UDP port
unsigned int localPort = UDP_PORT;
WiFiUDP Udp;

time_t getNtpTime();
void sendNTPpacket(IPAddress &address);

void time_init() {
    Serial.println("Starting UDP");
    Udp.begin(localPort);
    Serial.print("Local port: ");
    Serial.println(Udp.localPort());
    Serial.println("waiting for sync");
    setSyncProvider(getNtpTime);
    setSyncInterval(300);
}

time_t prevDisplay = 0; // when the digital clock was displayed

void time_update() {
    if (timeStatus() != timeNotSet) {
        if (now() != prevDisplay) { //update the display only if time has changed
            prevDisplay = now();
            digitalClockDisplay();
        }
    }
}

void digitalClockDisplay() {
  // digital clock display of the time
  Serial.print(hour());
  Serial.print(":");
  Serial.print(minute());
  Serial.print(":");
  Serial.print(second());
  Serial.print(" ");
  Serial.print(day());
  Serial.print(".");
  Serial.print(month());
  Serial.print(".");
  Serial.print(year());
  Serial.println();
}


/*-------- 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
}

// send an NTP request to the time server at the given address
void sendNTPpacket(IPAddress &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();
}