import com.LabJack.GenericSPI;

/**
 * SPI class for the Linear Technology LTC2413 ADC.
 *
 * <p>This class extends Generic by interpreting the raw conversion results from
 * a Linear Technology LTC2413 ADC.</p>
 */
public class LTC2413 extends GenericSPI
{
	public static class LTC2413Exception extends Exception
	{
		public final static int CONVERSION_INCOMPLETE = 0;
		public final static int OVERRANGE = 1;
		public final static int UNDERRANGE = 2;

		public LTC2413Exception( int cause )
		{
			super( getMessage( cause ) );
		}

		static String getMessage( int cause )
		{
			switch( cause )
			{
			case CONVERSION_INCOMPLETE:
				return "Conversion incomplete";

			case OVERRANGE:
				return "Measurement over-range";

			case UNDERRANGE:
				return "Measurement under-range";

			default:
				return "Unknown cause";
			}
		}
	}

	float reference;

	/**
	 * Constructor.
	 *
	 * @param	reference	Voltage reference value used for scaling LTC2413 conversion results.
	 */
	public LTC2413( float reference )
	{
		super( 32 );
		this.reference = reference;
	}

	/**
	 * Decodes and returns voltage reading.
	 *
	 * @return		Voltage reading.
	 *
	 * @throws		LTC2413Exception
	 */
	public float getVoltage() throws LTC2413Exception
	{
		int bits = getBits();

		if( ( bits & 0x80000000 ) != 0 )
		{
			throw new LTC2413Exception( LTC2413Exception.CONVERSION_INCOMPLETE );
		}

		boolean sign = ( bits & 0x20000000 ) != 0 ? true : false;	// true = positive
		int conversion = bits & 0x1fffffff;

		if( sign && ( bits & 0x10000000 ) != 0 )
		{
			throw new LTC2413Exception( LTC2413Exception.OVERRANGE );
		}
		else if( !sign && ( ( bits & 0x10000000 ) == 0 ) )
		{
			throw new LTC2413Exception( LTC2413Exception.UNDERRANGE );
		}

		float result = reference / 2f * (float)conversion / 0x0fffffff;

		if( !sign )
		{
			result = -result;
		}

		return result;
	}
}