added NTP time example

Author: Heltec-Aaron-Lee

examples/TimeNTP_ESP32WiFi/TimeNTP_ESP32WiFi.ino

@@ -0,0 +1,150 @@
+/*
+ * TimeNTP_ESP32WiFi.ino
+ * Example showing time sync to NTP time source
+ *
+ * This sketch uses the ESP32WiFi library
+ * This sketch uses the Time library https://github.com/PaulStoffregen/Time
+ */
+
+#include <TimeLib.h>
+#include <WiFi.h>
+#include <WiFiUdp.h>
+
+const char ssid[] = "ssid";  //  your network SSID (name)
+const char pass[] = "password";       // your network password
+
+// NTP Servers:
+static const char ntpServerName[] = "pool.ntp.org";
+
+const int timeZone = 0;     // UTC
+
+WiFiUDP Udp;
+unsigned int localPort = 8888;  // local port to listen for UDP packets
+
+time_t getNtpTime();
+void digitalClockDisplay();
+void printDigits(int digits);
+void sendNTPpacket(IPAddress &address);
+
+void setup()
+{
+  Serial.begin(115200);
+  while (!Serial) ; // Needed for Leonardo only
+  delay(250);
+  Serial.println("TimeNTP Example");
+  Serial.print("Connecting to ");
+  Serial.println(ssid);
+  WiFi.disconnect();
+  WiFi.mode(WIFI_MODE_STA);
+  WiFi.begin(ssid, pass);
+
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    Serial.print(".");
+  }
+
+  Serial.print("IP number assigned by DHCP is ");
+  Serial.println(WiFi.localIP());
+  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 loop()
+{
+  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());
+  printDigits(minute());
+  printDigits(second());
+  Serial.print(" ");
+  Serial.print(day());
+  Serial.print(".");
+  Serial.print(month());
+  Serial.print(".");
+  Serial.print(year());
+  Serial.println();
+}
+
+void printDigits(int digits)
+{
+  // utility for digital clock display: prints preceding colon and leading 0
+  Serial.print(":");
+  if (digits < 10)
+    Serial.print('0');
+  Serial.print(digits);
+}
+
+/*-------- 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();
+}