feat: new example for async update

Author: HoustonAsh

examples/AsyncUpdate/AsyncUpdate.ino

@@ -0,0 +1,48 @@
+#include <WiFi.h>
+#include <WiFiUdp.h>
+
+#include "NTPClient.h"
+
+#define SSID "<your-ssid>"
+#define PASSWORD "<your-password>"
+
+WiFiUDP ntpUDP;
+NTPClient timeClient(ntpUDP, "0.asia.pool.ntp.org", 0, 1500);
+
+void setup(){
+  Serial.begin(115200);
+
+  WiFi.begin(SSID, PASSWORD);
+
+  while ( WiFi.status() != WL_CONNECTED ) {
+    delay ( 500 );
+    Serial.print ( "." );
+  }
+
+  timeClient.begin();
+}
+
+void loop() {
+  long int loopMillis = millis();
+  static int prevRes = 0;
+  // with update() method loop will be blocked until time is updated
+  // timeClient.update();
+  int res = timeClient.asyncUpdate();
+
+  if (res != prevRes) {
+    Serial.printf("Result: %d\n", res);
+    prevRes = res;
+  }
+
+  static long int lm = 0;
+
+  if (millis() - lm > 1000) {
+    lm = millis();
+    Serial.printf("%s.%d\n", timeClient.getFormattedTime().c_str(), int(timeClient.getEpochTimeMillis()%1000));
+  }
+
+  long int dd = millis() - loopMillis;
+  if (dd > 10) {
+    Serial.printf("Loop took %d ms...\n", dd);
+  }
+}