//=====================================================================
// Class Constructor
//=====================================================================
/// <summary>
/// Set the address of the luminosity sensor and set the clock speed
/// </summary>
public TSL2561BusSensor() : base(BUS_ADDRESS, CLOCK_SPEED)
{
// Determine the current timing settings
byte command = (byte)CommandOptions.CommandBit | (byte)Registers.Timing;
byte[] options = new byte[1]; // Will hold registry values
ReadRegister(command, options);
// Determine the timing settings
_gain = (GainOptions)(options[0] & (byte)GainOptions.High);
_intPeriod = (IntegrationOptions)(options[0] & 0x03);
}
//=====================================================================
// SetTiming
//=====================================================================
public void SetTiming(GainOptions gain, IntegrationOptions integration)
{
// Set the commands
byte command = (byte)CommandOptions.CommandBit | (byte)Registers.Timing;
byte options = (byte)((byte)gain | (byte)integration);
// Write the timing information
EnableSensor();
WriteRegister(command, options);
DisableSensor();
// Update the object
_gain = gain;
_intPeriod = integration;
}
//=====================================================================
// readOptimizedLuminosity
//=====================================================================
public double readOptimizedLuminosity()
{
//-----------------------------------------------------------------
// Read the sensor measurements
//-----------------------------------------------------------------
// Initialize values
double luminosity = LUX_ERROR;
bool luxCaptured = false;
UInt16 chan0 = 0;
UInt16 chan1 = 0;
// Sensor signal checks
while (!luxCaptured)
{
// Get the measured luminosity in both channels
chan0 = GetChannelData(Channels.Channel0);
chan1 = GetChannelData(Channels.Channel1);
// Evaluate the signal strength
if ((chan0 == 0xFFFF) || (chan1 == 0xFFFF)) // Saturated signal
// Sensor saturated, so adjust timing
{
if (_gain == GainOptions.High)
{
_gain = GainOptions.Low; // Lower the gain
}
else if ((int)_intPeriod > 0)
{
--_intPeriod; // Reduce the integration time
}
else
{
luxCaptured = true; // Can't make any further adjustments
}
}
else if ((chan0 < 10) || (chan1 < 10)) // Low signal
// Low signal, so again try adjusting timing
{
if ((int)_intPeriod < 2)
{
++_intPeriod; // Increase the integration time
}
else if (_gain == GainOptions.Low)
{
_gain = GainOptions.High; // Increase the gain
}
else
{
luminosity = readLuminosity(); // The measured value is the best one
luxCaptured = true;
}
}
else
{
luxCaptured = true; // Signal is fine, return from loop and calculate
}
// Make adjustments if needed
if (!luxCaptured)
{
SetTiming(_gain, _intPeriod); // A bit crude, but fine for now
}
}
if (chan0 != 0) // Check for division by zero
//-----------------------------------------------------------------
// Determine scaling
//-----------------------------------------------------------------
{
double scale;
// First, account for integration time
switch (_intPeriod)
{
case IntegrationOptions.Short:
scale = 402.0 / 13.7;
break;
case IntegrationOptions.Medium:
scale = 402.0 / 101.0;
break;
default:
scale = 1.0;
break;
}
// Adjust for gain
if (_gain == GainOptions.Low)
{
scale *= 16.0;
}
//-----------------------------------------------------------------
// Calculate luminosity
//-----------------------------------------------------------------
// Scale the readings
double d0 = scale * chan0;
double d1 = scale * chan1;
// Calculation from the TSL2561 datasheet
double ratio = (double)chan1 / (double)chan0;
if (ratio <= 0.5)
{
luminosity = 0.0304 * d0 - 0.062 * System.Math.Pow(ratio, 1.4) * d0;
}
else if (ratio <= 0.61)
{
luminosity = 0.0224 * d0 - 0.031 * d1;
}
else if (ratio <= 0.8)
{
luminosity = 0.0128 * d0 - 0.0153 * d1;
}
else if (ratio <= 1.3)
{
luminosity = 0.00146 * d0 - 0.00112 * d1;
}
else
{
luminosity = 0.0;
}
}
else
{
luminosity = 0.0; // Set luminosity to zero
}
return(luminosity);
}
