/*
  BTArduino sketch
  By Edward Mitchell
  http://appinventor.pevest.com
  
  Description:
  Uses the JY-MCU Bluetooth module to enable an Arduino board to communicate over Bluetooth
  wireless to an Android app written in MIT App Inventor 2, running on an Android device.
  
  Buy the JY-MCU module here
  (Amazon Prime) http://www.amazon.com/gp/product/B0093XAV4U/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0093XAV4U&linkCode=as2&tag=commonsensevi-20&linkId=4L5VQJW7JJKBGCMU
  (Amazon non Prime option) http://www.amazon.com/gp/product/B009DZQ4MG/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B009DZQ4MG&linkCode=as2&tag=commonsensevi-20&linkId=S6VEEZVTF4GBGYWC
  
  Credit:  
  This Arduino code based very loosely on the original Arduino code for the JY-MCU Bluetooth module tutorial at
  http://robotosh.blogspot.com/2012/07/arduino-jy-mcu-bluetooth.html
  
  A tutorial for using this code with App Inventor 2, is available at the appinventor.pevest.com
  web site. Please refer to the tutorial for information and source code for the Android side of this sketch.
  
  Note - this sample code is intended only to show how the basic Bluetooth communications link may
  be set up, and illustrates just one possible way of sending commands from the Android device
  to the Arduino phone. The purpose of this code is as an introduction/tutorial and is not meant
  to be used for any particular purpose. No warranties.
*/

// Constant Definitions
#define LEDPIN 8 // Pin on Arduino board to which status LED is connected
#define READ_RATE 100 // How often the serial link is read, in milliseconds
#define FLASH_RATE 100 // The on/off period in milliseconds, for the LED Flash status feedback


// Declarations
byte cmd;  // Stores the next byte of incoming data, which is a "command" to do something 
byte param; // Stores the 2nd byte, which is the command parameter


// Initialization
void setup() {

  pinMode(LEDPIN, OUTPUT);  // pin 48 (on-board LED) as OUTPUT
  digitalWrite(LEDPIN, LOW);
  Serial.begin(9600);       // start serial communication at 9600bps
}


// Arduino Execution Loop
void loop() {

  if ( Serial.available() )       // if data is available to read
  {
    cmd = Serial.read();         // read it and store it in 'cmd'
    // Data format is byte 1 = command, byte 2 = parameter
  };
  
  switch ( cmd ) {
    case 1:
      // First byte contains a generic "command" byte. We arbitrarily defined '1' as the command to then check the 2nd parameter byte
      // User can additional commands by adding case 2, 3, 4, etc
      {
         // read the parameter byte
         param = Serial.read();
         switch (param)
         {
           case 1: 
             // Android device requests the Arduino to send some data back to Android
             flashLED(1);
             if (Serial)
             {
               // Send back 2 bytes with a value of 1, 2
               Serial.write(1);
               Serial.write(2);
             };
             break;
           case 2:
             // Turn on status LED
             flashLED(2);
             digitalWrite(LEDPIN, HIGH );
             break;
           case 3: 
             // Turn off status LED
             flashLED(3);
             digitalWrite(LEDPIN, LOW);
             break;
           case 4:
              // Demonstrate flashing the LED 4 times
              flashLED(4);
              break;
           case 5:
              // Demonstrate flashing the LED 5 times
              // Could add code here to control a servo via PWM outputs
              flashLED(5);
              break;
           default: break; // do nothing
         } // switch (param)
      } // switch (cmd) case 1
      default: break; // do nothing
  } // switch (cmd)
  
  delay(READ_RATE);                    // wait 100ms for next reading
}

  // Support routine
void flashLED (int n) {
  // Flash the LED n times, to provide an on board status indicator
  for (int i=1; i<=n; i++) {
    digitalWrite (LEDPIN, HIGH);
    delay (FLASH_RATE);
    digitalWrite (LEDPIN, LOW);
    delay(FLASH_RATE);
  };
  return;
}