Update Overview.md

docs/Overview.md

@@ -211,7 +211,7 @@ struct TableLamp : Service::LightBulb {};
   
   boolean update(){                          // update() method
 
-    digitalWrite(ledPin,power->getNewVal());     // use standard Arduino digitalWrite function to change the ledPin to either high or low based on the value requested by HomeKit
+    digitalWrite(lampPin,lampPower->getNewVal());      // use standard Arduino digitalWrite function to change the ledPin to either high or low based on the value requested by HomeKit
    
     return(true);                            // return true to let HomeKit (and the Home App Client) know the update was successful
   
@@ -220,6 +220,78 @@ struct TableLamp : Service::LightBulb {};
 };
 ```
 
+Finally, we append our derived TableLamp Service to the original sketch and replace the instantiation of our generic LightBulb Service and On Characteristic:
+
+```C++
+new Service::LightBulb();                       // Create the Light Bulb Service
+  new Characteristic::On();                       // Characteristic that stores that state of the light bulb: ON or OFF
+```
+
+with the instantiation of the TableLamp Service as such:
+
+```C++
+new TableLamp(13);
+```
+
+where 13 specifies the ESP32 pin number that is connected to the hypothetical relay used to turn the Table Lamp on and off.  Our completed HomeSpan sketch looks like this:
+
+```C++
+/* HomeSpan Table Lamp Example */
+
+#include "HomeSpan.h"         // include the HomeSpan library
+
+void setup() {     
+ 
+  Serial.begin(115200);       // start the Serial interface
+  
+  homeSpan.begin();           // initialize HomeSpan
+
+  new SpanAccessory();           // Table Lamp Accessory
+  
+    new Service::AccessoryInformation();            // HAP requires every Accessory to implement an AccessoryInformation Service, with 6 *required* Characteristics
+      new Characteristic::Name("My Table Lamp");      // Name of the Accessory, which shows up on the HomeKit "tiles", and should be unique across Accessories                                                    
+      new Characteristic::Manufacturer("HomeSpan");   // Manufacturer of the Accessory (arbitrary text string, and can be the same for every Accessory)
+      new Characteristic::SerialNumber("123-ABC");    // Serial Number of the Accessory (arbitrary text string, and can be the same for every Accessory)
+      new Characteristic::Model("120-Volt Lamp");     // Model of the Accessory (arbitrary text string, and can be the same for every Accessory)
+      new Characteristic::FirmwareRevision("0.9");    // Firmware of the Accessory (arbitrary text string, and can be the same for every Accessory)  
+      new Characteristic::Identify();                 // Provides a hook that allows a HomeKit Client to identify the device
+  
+    new Service::HAPProtocolInformation();          // HAP requires every Accessory (except those in a bridfge) to implement a Protcol Information Service  
+      new Characteristic::Version("1.1.0");           // Set the Version Characteristic to "1.1.0," which is required by HAP
+      
+   new TableLamp(13);                               // instantiate the TableLamp Service (defined below) with lampPin set to 17
+  
+} // end of setup()
+
+void loop(){
+
+ homeSpan.poll(); 
+
+} // end of loop()
+
+struct TableLamp : Service::LightBulb {};
+
+  int lampPin;                               // store the pin number connected to a hypothetical relay that turns the Table Lamp on/off
+  SpanCharacteristic *lampPower;             // store a reference to the On Characteristic
+  
+  TableLamp(int lampPin) : Service::LightBulb(){       // constructor() method for TableLamp defined with one parameter.  Note we also call the constructor() method for the LightBulb Service.
+
+    lampPower=new Characteristic::On();      // instantiate the On Characteristic and save it as lampPower
+    this->lampPin=lampPin;                   // save the pin number for the hypothetical relay
+    pinMode(lampPin,OUTPUT);                 // configure the pin as an output using the standard Arduino pinMode function                       
+    
+  } // end constructor()
+  
+  boolean update(){                          // update() method
+
+    digitalWrite(lampPin,lampPower->getNewVal());      // use standard Arduino digitalWrite function to change the ledPin to either high or low based on the value requested by HomeKit
+   
+    return(true);                            // return true to let HomeKit (and the Home App Client) know the update was successful
+  
+  } // end update()
+  
+};
+```