//
// LED-based proximity switch demonstration.
// White LED is connected to P1_7
// Red LED is connected to P1_4
// Both of these LEDs are external to the Launchpad (not the built-in LEDs).
// They are arranged so that they are right next to one another.
// This lets the white LED illuminate anything in front of it.
// The red LED is used as a sensor, to detect anything close enough to the white LED to be brightly lit.
//
// When you place your finger or a white card in front of the two LEDs, the program turns on the on-board green LED,
// and sends text to the development computer telling what the light level was.
//

unsigned long int no_signal = 0;

void
setup( void )
{
  analogReference( INTERNAL1V5 );
  pinMode( A4, INPUT );
  pinMode( P1_7, OUTPUT );
  pinMode( GREEN_LED, OUTPUT );
  digitalWrite( P1_7, HIGH );
  Serial.begin( 9600 );
  
  for( int x = 0; x < 100; x++ )
  {
    delay( 10 );
    int val = analogRead( A4 );
    if( val > no_signal )
      no_signal = val;
  }

  Serial.println( no_signal );
}

void
loop( void )
{
  unsigned int level = (100 * analogRead( A4 ) ) / no_signal;
  Serial.print( level );
  if( level < 50 )
  {
    digitalWrite( GREEN_LED, HIGH );
    Serial.println( "% ON" );
  }
  else
  {
    digitalWrite( GREEN_LED, LOW );
    Serial.println( "% OFF" );
  }
}