Added comment to the ModbusRTUTemperatureSensor example

added some comments to the ModbusRTUTemperatureSensor example

Author: Rocketct

examples/RTU/ModbusRTUTemperatureSensor/ModbusRTUTemperatureSensor.ino

@@ -1,27 +1,31 @@
 /*
   Modbus RTU Temeperature Sensor
 
-  This sketch show how to use the modbus library, in in order to sent a request to a slave RTU sensor
-  unit and read the responce packet return by the remote unit.
+  This sketch shows you how to interact with a Modbus RTU temperature and humidity sensor.
+  It reads the temperature and humidity values every 5 seconds and outputs them to the
+  serial monitor.
 
   Circuit:
    - MKR board
-   - TModbus RS485 Temperature
+   - Modbus RS485 Temperature:
+   - External power Supply
    - MKR 485 shield
-     - ISO GND connected to GND of the Modbus RTU server
+     - ISO GND connected to GND of the Modbus RTU sensor and the Power supply V-;
+     - Power supply V+ connected to V+ sensor
      - Y connected to A/Y of the Modbus RTU sensor
      - Z connected to B/Z of the Modbus RTU sensor
      - Jumper positions
        - FULL set to OFF
-       - Z \/\/ Y set to OFF
+       - Z \/\/ Y set to ON
 
-  created 16 July 2018
-  by Sandeep Mistry
+  created 8 August 2018
+  by Riccardo Rizzo
 */
 
 #include <ArduinoModbus.h>
 
-float temperature, humidity;
+float temperature;
+float humidity;
 
 void setup() {
   Serial.begin(9600);
@@ -36,19 +40,26 @@ void setup() {
 }
 
 void loop() {
-  //send a reading request to the RTU slave with id=1, type=HOLDING_REGISTERS address=0, number of values to read, nb=2
+
+  // send a Holding registers read request to (slave) id 1, for 2 registers
   if (!ModbusRTUClient.requestFrom(1, HOLDING_REGISTERS, 0x00, 2)) {
     Serial.print("failed to read registers! ");
     Serial.println(ModbusRTUClient.lastError());
   } else {
-    //if the request goes fine read the value with the read() function
+
+    // If the request goes fine, the sensor sent the readings as bytes packet,
+    // through the read() function is possible read the measurments.
+    // the readings is parsed as a short integer from the packets
     short rawtemperature = ModbusRTUClient.read();
     short rawhumidity = ModbusRTUClient.read();
+
+    // Is required divide by 10.0 the value readed, because the sensor sent the
+    // readings as an integer obtained multipling the float value readed by 10
     temperature = rawtemperature / 10.0;
     humidity = rawhumidity / 10.0;
     Serial.println(temperature);
     Serial.println(humidity);
   }
 
   delay(5000);
-}
+}