kitchen_pilot_wire_control.ino: make code more readable

soft/kitchen/kitchen_pilot_wire_control/kitchen_pilot_wire_control.ino

@@ -19,21 +19,29 @@ EspMQTTClient client(
 
 const int heating_pin = 14;
 
+#define heater_on(pin) do {\
+  digitalWrite(pin, LOW); \
+} while(0)
+
+#define heater_off(pin) do {\
+  digitalWrite(pin, HIGH); \
+} while(0)
+
 void message_callback(const String &message)
 {
   Serial.println(message);
   if (message == "off") {
-      digitalWrite(heating_pin, HIGH);
+      heater_off(heating_pin);
   }
   if (message == "on") {
-      digitalWrite(heating_pin, LOW);
+      heater_on(heating_pin);
   }
 }
 
 void setup()
 {
   pinMode(heating_pin, OUTPUT);
-  digitalWrite(heating_pin, HIGH); // by default output the voltage that switches off the heater
+  heater_off(heating_pin);
 
   Serial.begin(115200);
 
@@ -56,6 +64,6 @@ void loop()
   client.loop();
   if (!client.isConnected()) {
     // if something wrong happens, switch off the heater
-    digitalWrite(heating_pin, HIGH);
+    heater_off(heating_pin);
   }
 }