Use library for NTP data handling

libraries/RTC/examples/RTC_NTPSync/RTC_NTPSync.ino

@@ -4,14 +4,16 @@
  * Then the current time from the RTC is printed to the Serial port.
  * 
  * Instructions:
- * 1. Change the WiFi credentials in the arduino_secrets.h file to match your WiFi network.
- * 2. Upload this sketch to Portenta C33 / UNO R4 WiFi.
- * 3. Open the Serial Monitor.
+ * 1. Download the NTPClient library (https://github.com/arduino-libraries/NTPClient) through the Library Manager
+ * 2. Change the WiFi credentials in the arduino_secrets.h file to match your WiFi network.
+ * 3. Upload this sketch to Portenta C33 / UNO R4 WiFi.
+ * 4. Open the Serial Monitor.
  * 
  * Initial author: Sebastian Romero @sebromero
  */
 
 #include "RTC.h"
+#include <NTPClient.h>
 
 #if defined(ARDUINO_PORTENTA_C33)
 #include <WiFiC3.h>
@@ -26,36 +28,9 @@
 char ssid[] = SECRET_SSID;        // your network SSID (name)
 char pass[] = SECRET_PASS;    // your network password (use for WPA, or use as key for WEP)
 
-constexpr unsigned int LOCAL_PORT = 2390;      // local port to listen for UDP packets
-constexpr int NTP_PACKET_SIZE = 48; // NTP timestamp is in the first 48 bytes of the message
-
 int wifiStatus = WL_IDLE_STATUS;
-IPAddress timeServer(162, 159, 200, 123); // pool.ntp.org NTP server
-byte packetBuffer[NTP_PACKET_SIZE]; //buffer to hold incoming and outgoing packets
 WiFiUDP Udp; // A UDP instance to let us send and receive packets over UDP
-
-// send an NTP request to the time server at the given address
-unsigned long 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();
-}
+NTPClient timeClient(Udp);
 
 void printWifiStatus() {
   // print the SSID of the network you're attached to:
@@ -102,56 +77,21 @@ void connectToWiFi(){
   printWifiStatus();
 }
 
-/**
- * Calculates the current unix time, that is the time in seconds since Jan 1 1970.
- * It will try to get the time from the NTP server up to `maxTries` times,
- * then convert it to Unix time and return it.
- * You can optionally specify a time zone offset in hours that can be positive or negative.
-*/
-unsigned long getUnixTime(int8_t timeZoneOffsetHours = 0, uint8_t maxTries = 5){
-  // Try up to `maxTries` times to get a timestamp from the NTP server, then give up.
-  for (size_t i = 0; i < maxTries; i++){
-    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");
-      Udp.read(packetBuffer, NTP_PACKET_SIZE); // read the packet into the buffer
-
-      //the timestamp starts at byte 40 of the received packet and is four bytes,
-      //or two words, long. First, extract the two words:
-      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;
-
-      // Now convert NTP time into everyday time:
-      // Unix time starts on Jan 1 1970. In seconds, that's 2208988800:
-      const unsigned long seventyYears = 2208988800UL;
-      unsigned long secondsSince1970 = secsSince1900 - seventyYears + (timeZoneOffsetHours * 3600);
-      return secondsSince1970;
-    }
-  }
-
-  return 0;
-}
-
 void setup(){
   Serial.begin(9600);
   while (!Serial);
 
   connectToWiFi();
-  Serial.println("\nStarting connection to server...");
-  Udp.begin(LOCAL_PORT);
   RTC.begin();
+  Serial.println("\nStarting connection to server...");
+  timeClient.begin();
+  timeClient.update();
 
   // Get the current date and time from an NTP server and convert
   // it to UTC +2 by passing the time zone offset in hours.
   // You may change the time zone offset to your local one.
-  auto unixTime = getUnixTime(2);
+  auto timeZoneOffsetHours = 2;
+  auto unixTime = timeClient.getEpochTime() + (timeZoneOffsetHours * 3600);
   Serial.print("Unix time = ");
   Serial.println(unixTime);
   RTCTime timeToSet = RTCTime(unixTime);