kitchen_pilot_wire_control.ino: switch off heater if no order for an hour

soft/kitchen/kitchen_pilot_wire_control/kitchen_pilot_wire_control.ino

@@ -27,6 +27,16 @@ const int heating_pin = 14;
   digitalWrite(pin, HIGH); \
 } while(0)
 
+
+os_timer_t keep_alive_timer;
+
+void reset_timer(os_timer_t *timer)
+{
+  os_timer_disarm(timer);
+  os_timer_setfn(timer, shutdown_heater, NULL);
+  os_timer_arm(timer, 3600000, false);
+}
+
 void message_callback(const String &message)
 {
   Serial.println(message);
@@ -36,6 +46,14 @@ void message_callback(const String &message)
   if (message == "on") {
       heater_on(heating_pin);
   }
+  reset_timer(&keep_alive_timer);
+}
+
+void shutdown_heater(void *dummy)
+{
+  // if we didn't receive a message for an hour,
+  // shutdown the heater
+  heater_off(heating_pin);
 }
 
 void setup()
@@ -49,6 +67,8 @@ void setup()
   client.enableDebuggingMessages(); // Enable debugging messages sent to serial output
   client.enableHTTPWebUpdater(); // Enable the web updater. User and password default to values of MQTTUsername and MQTTPassword. These can be overrited with enableHTTPWebUpdater("user", "password").
   //client.enableLastWillMessage("TestClient/lastwill", "I am going offline");  // You can activate the retain flag by setting the third parameter to true
+  os_timer_setfn(&keep_alive_timer, shutdown_heater, NULL);
+  os_timer_arm(&keep_alive_timer, 3600000, false);
 }
 
 // This function is called once everything is connected (Wifi and MQTT)