add io time interval example

examples/adafruitio_time_esp8266/adafruitio_time_esp8266.ino

@@ -0,0 +1,81 @@
+#include <ESP8266WiFi.h>
+#include "Adafruit_MQTT.h"
+#include "Adafruit_MQTT_Client.h"
+
+/************************* WiFi Access Point *********************************/
+#define WLAN_SSID       "network"
+#define WLAN_PASS       "password"
+
+/************************* Adafruit.io Setup *********************************/
+#define AIO_SERVER      "io.adafruit.com"
+#define AIO_SERVERPORT  8883
+#define AIO_USERNAME    "user"
+#define AIO_KEY         "key"
+
+WiFiClientSecure client;
+Adafruit_MQTT_Client mqtt(&client, AIO_SERVER, AIO_SERVERPORT, AIO_USERNAME, AIO_USERNAME, AIO_KEY);
+
+Adafruit_MQTT_Subscribe timefeed = Adafruit_MQTT_Subscribe(&mqtt, "time/seconds");
+
+// set timezone offset from UTC
+int timeZone = -4; // UTC - 4 eastern daylight time (nyc)
+int interval = 4; // trigger every X hours
+int hour = 0; // current hour
+
+void timecallback(uint32_t current) {
+
+  // stash previous hour
+  int previous = hour;
+
+  // adjust to local time zone
+  current += (timeZone * 60 * 60);
+
+  // calculate current hour
+  hour = (current / 60 / 60) % 24;
+
+  // only trigger on interval
+  if((hour != previous) && (hour % interval) == 0) {
+    Serial.println("Run your code here");
+  }
+
+}
+
+void setup() {
+
+  Serial.begin(115200);
+  delay(10);
+
+  Serial.print(F("Adafruit IO Time Demo"));
+
+  WiFi.begin(WLAN_SSID, WLAN_PASS);
+  while (WiFi.status() != WL_CONNECTED) {
+    delay(500);
+    Serial.print(F("."));
+  }
+  Serial.println(F(" WiFi connected."));
+
+  timefeed.setCallback(timecallback);
+  mqtt.subscribe(&timefeed);
+
+}
+
+void loop() {
+
+  int8_t code;
+
+  // connect to adafruit io if not connected
+  if(! mqtt.connected()) {
+
+    Serial.print("Connecting to Adafruit IO... ");
+    if((code = mqtt.connect()) != 0) {
+      Serial.println(mqtt.connectErrorString(code));
+      while(1);
+    }
+    Serial.println("connected!");
+
+  }
+
+  mqtt.processPackets(1000);
+  mqtt.ping();
+
+}