 // In order to receive, attach a callback function to these events
 enum
 {
-  // Commands
-  kAcknowledge         , // Command to acknowledge that cmd was received
-  kError               , // Command to report errors
-  kFloatAddition       , // Command to request add two floats
-  kFloatAdditionResult , // Command to report addition result
+  kSetLed              , // Command to request led to be set in specific state
+  kStatus              , // Command to report status
 };
 
-// Commands we send from the PC and want to receive on the Arduino.
-// We must define a callback function in our Arduino program for each entry in the list below.
-
+// Callbacks define on which received commands we take action
 void attachCommandCallbacks()
 {
   // Attach callback methods
   cmdMessenger.attach(OnUnknownCommand);
-  cmdMessenger.attach(kFloatAddition, OnFloatAddition);
+  cmdMessenger.attach(kSetLed, OnSetLed);
 }
-
-// ------------------  C A L L B A C K S -----------------------
 
 // Called when a received command has no attached function
 void OnUnknownCommand()
 {
-  cmdMessenger.sendCmd(kError,"Command without attached callback");
+  cmdMessenger.sendCmd(kStatus,"Command without attached callback");
 }
 
-// Callback function that responds that Arduino is ready (has booted up)
-void OnArduinoReady()
+// Callback function that sets led on or off
+void OnSetLed()
 {
-  cmdMessenger.sendCmd(kAcknowledge,"Arduino ready");
+  // Read led state argument, interpret string as boolean
+  ledState = cmdMessenger.readBoolArg();
+  // Set led
+  digitalWrite(kBlinkLed, ledState?HIGH:LOW);
+  // Send back status that describes the led state
+  cmdMessenger.sendCmd(kStatus,(int)ledState);
 }
-
-// Callback function calculates the sum of the two received float values
-void OnFloatAddition()
-{
-  // Retreive first parameter as float
-  float a = cmdMessenger.readFloatArg();
-  
-  // Retreive second parameter as float
-  float b = cmdMessenger.readFloatArg();
-  
-  // Send back the result of the addition
-  //cmdMessenger.sendCmd(kFloatAdditionResult,a + b);
-  cmdMessenger.sendCmdStart(kFloatAdditionResult);
-  cmdMessenger.sendCmdArg(a+b);
-  cmdMessenger.sendCmdArg(a-b);
-  cmdMessenger.sendCmdEnd();
-}
-
-// ------------------ M A I N  ----------------------
 
 // Setup function
 void setup() 
 {
-  // Listen on serial connection for messages from the pc
+  // Listen on serial connection for messages from the PC
   Serial.begin(115200); 
 
   // Adds newline to every command

{
  // Process incoming serial data, and perform callbacks
  cmdMessenger.feedinSerialData();

  // Toggle LED periodically. If the LED does not toggle every 2000 ms, 
  // this means that cmdMessenger are taking a longer time than this  
  if (hasExpired(previousToggleLed,2000)) // Toggle every 2 secs
  {
    toggleLed();  
  } 
}

// Toggle led state 
void toggleLed()
{  
  ledState = !ledState;
  digitalWrite(kBlinkLed, ledState?HIGH:LOW);
}  

  attachCommandCallbacks();

  // Send the status to the PC that says the Arduino has booted
  // Note that this is a good debug function: it will let you also know 
  // if your program had a bug and the arduino restarted  
  cmdMessenger.sendCmd(kStatus,"Arduino has started!");

  // set pin for blink LED
  pinMode(kBlinkLed, OUTPUT);
}

// Loop function
