AsyncUdpNTPClient.ino

/****************************************************************************************************************************
  AsyncUdpNTPClient.ino
  
  For STM32 with built-in LAN8742A Ethernet (Nucleo-144, DISCOVERY, etc)
  
  AsyncUDP_STM32 is a Async UDP library for the STM32 using built-in LAN8742A Ethernet
  
  Based on and modified from ESPAsyncUDP Library (/~https://github.com/me-no-dev/ESPAsyncUDP)
  Built by Khoi Hoang /~https://github.com/khoih-prog/AsyncUDP_STM32
  Licensed under MIT license
 *****************************************************************************************************************************/

#include "defines.h"
#include <time.h>

// 0.ca.pool.ntp.org
IPAddress timeServerIP = IPAddress(208, 81, 1, 244);
// time.nist.gov
//IPAddress timeServerIP = IPAddress(132, 163, 96, 1);

#define NTP_REQUEST_PORT      123

//char timeServer[] = "time.nist.gov";  // NTP server
char timeServer[] = "0.ca.pool.ntp.org";

const int NTP_PACKET_SIZE = 48;       // NTP timestamp 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
AsyncUDP Udp;

// send an NTP request to the time server at the given address
void createNTPpacket(void)
{
  Serial.println("============= createNTPpacket =============");

  // 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;
}

void parsePacket(AsyncUDPPacket packet)
{
  struct tm  ts;
  char       buf[80];
  
  memcpy(packetBuffer, packet.data(), sizeof(packetBuffer));

  Serial.print("Received UDP Packet Type: ");
  Serial.println(packet.isBroadcast() ? "Broadcast" : packet.isMulticast() ? "Multicast" : "Unicast");
  Serial.print("From: ");
  Serial.print(packet.remoteIP());
  Serial.print(":");
  Serial.print(packet.remotePort());
  Serial.print(", To: ");
  Serial.print(packet.localIP());
  Serial.print(":");
  Serial.print(packet.localPort());
  Serial.print(", Length: ");
  Serial.print(packet.length());
  Serial.println();

  unsigned long highWord = word(packetBuffer[40], packetBuffer[41]);
  unsigned long lowWord = word(packetBuffer[42], packetBuffer[43]);

  // 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(F("Seconds since Jan 1 1900 = "));
  Serial.println(secsSince1900);

  // now convert NTP time into )everyday time:
  Serial.print(F("Epoch/Unix time = "));
  
  // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
  const unsigned long seventyYears = 2208988800UL;
  
  // subtract seventy years:
  unsigned long epoch = secsSince1900 - seventyYears;
  time_t epoch_t = epoch;   //secsSince1900 - seventyYears;
 
  // print Unix time:
  Serial.println(epoch);

  // print the hour, minute and second:
  Serial.print(F("The UTC/GMT time is "));       // UTC is the time at Greenwich Meridian (GMT)

  ts = *localtime(&epoch_t);
  strftime(buf, sizeof(buf), "%a %Y-%m-%d %H:%M:%S %Z", &ts);
  Serial.println(buf);
}

void sendNTPPacket(void)
{
  createNTPpacket();
  //Send unicast
  Udp.write(packetBuffer, sizeof(packetBuffer));
}

void setup()
{
  Serial.begin(115200);
  while (!Serial);

  Serial.print("\nStart AsyncUdpNTPClient on "); Serial.println(BOARD_NAME);
  Serial.println(ASYNC_UDP_STM32_VERSION);

#if (_ASYNC_UDP_STM32_LOGLEVEL_ > 2)
  Serial.print("STM32 Core version v"); Serial.print(STM32_CORE_VERSION_MAJOR);
  Serial.print("."); Serial.print(STM32_CORE_VERSION_MINOR); 
  Serial.print("."); Serial.println(STM32_CORE_VERSION_PATCH);
#endif

  // start the ethernet connection and the server
  // Use random mac
  uint16_t index = millis() % NUMBER_OF_MAC;

  // Use Static IP
  //Ethernet.begin(mac[index], ip);
  // Use DHCP dynamic IP and random mac
  Ethernet.begin(mac[index]);

  // you're connected now, so print out the data
  Serial.print(F("You're connected to the network, IP = "));
  Serial.println(Ethernet.localIP());

  //NTP requests are to port NTP_REQUEST_PORT = 123
  if (Udp.connect(timeServerIP, NTP_REQUEST_PORT))
  //if (Udp.connect(timeServer, NTP_REQUEST_PORT))
  {
    Serial.println("UDP connected");

    Udp.onPacket([](AsyncUDPPacket packet)
    {
      parsePacket(packet);
    });
  }
}

void loop()
{
  sendNTPPacket();

  // wait 60 seconds before asking for the time again
  delay(60000);
}