protected override void OnCharacteristicValueChanged(GattCharacteristic sender, GattValueChangedEventArgs eventArgs)
{
if (sender.Uuid == IRTemperatureCharacteristicUuid)
{
if (_irTemperatureValueChanged != null)
{
uint dataLength = eventArgs.CharacteristicValue.Length;
using (DataReader reader = DataReader.FromBuffer(eventArgs.CharacteristicValue))
{
if (dataLength == 4)
{
var data = new byte[dataLength];
reader.ReadBytes(data);
IRTemperatureMeasurement measurement = new IRTemperatureMeasurement();
ushort objTemp = (ushort)(data[0] + (data[1] << 8));
ushort dieTemp = (ushort)(data[2] + (data[3] << 8));
if (Version == 1)
{
measurement.DieTemperature = dieTemp / 128.0;
double Vobj2 = (double)objTemp;
Vobj2 *= 0.00000015625;
double Tdie = measurement.DieTemperature + 273.15;
double S0 = 7E-14; // Calibration factor: todo: this factor needs to be computed via calibration step.
double a1 = 1.75E-3;
double a2 = -1.678E-5;
double b0 = -2.94E-5;
double b1 = -5.7E-7;
double b2 = 4.63E-9;
double c2 = 13.4;
double Tref = 298.15;
double S = S0 * (1 + a1 * (Tdie - Tref) + a2 * Math.Pow((Tdie - Tref), 2));
double Vos = b0 + b1 * (Tdie - Tref) + b2 * Math.Pow((Tdie - Tref), 2);
double fObj = (Vobj2 - Vos) + c2 * Math.Pow((Vobj2 - Vos), 2);
double tObj = Math.Pow(Math.Pow(Tdie, 4) + (fObj / S), .25);
measurement.ObjectTemperature = (tObj - 273.15);
}
else
{
const double SCALE_LSB = 0.03125;
int it;
it = (int)((objTemp) >> 2);
measurement.ObjectTemperature = (double)it * SCALE_LSB;
it = (int)((dieTemp) >> 2);
measurement.DieTemperature = (double)it * SCALE_LSB;
}
OnIRTemperatureMeasurementValueChanged(new IRTemperatureMeasurementEventArgs(measurement, eventArgs.Timestamp));
}
}
}
}
}
public IRTemperatureMeasurementEventArgs(IRTemperatureMeasurement measurement, DateTimeOffset timestamp)
{
Measurement = measurement;
Timestamp = timestamp;
}
protected override void OnCharacteristicValueChanged(GattCharacteristic sender, GattValueChangedEventArgs eventArgs)
{
if (sender.Uuid == IRTemperatureCharacteristicUuid)
{
if (_irTemperatureValueChanged != null)
{
uint dataLength = eventArgs.CharacteristicValue.Length;
using (DataReader reader = DataReader.FromBuffer(eventArgs.CharacteristicValue))
{
if (dataLength == 4)
{
var data = new byte[dataLength];
reader.ReadBytes(data);
IRTemperatureMeasurement measurement = new IRTemperatureMeasurement();
short objTemp = (short)((short)data[0] + (short)(data[1] << 8));
short dieTemp = (short)((short)data[2] + (short)(data[3] << 8));
if (Version == 1)
{
// This algorithm comes from http://www.ti.com/product/tmp006
measurement.DieTemperature = dieTemp / 128.0;
double Vobj2 = (double)objTemp;
Vobj2 *= 156.25E-9; // Voltage in the sensor
double toKelvin = 273.15;
double Tdie = measurement.DieTemperature + toKelvin;
double S0 = 6.4E-14; // Default value based on black body with ε = 0.95, and 110° FOV.
double a1 = 1.75E-3; // Default values based on typical sensor characteristics
double a2 = -1.678E-5;
double b0 = -2.94E-5;
double b1 = -5.7E-7; // Calibrate in end-application environment
double b2 = 4.63E-9;
double c2 = 13.4;
double Tref = 298.15;
// compute the sensitivity of the thermopile sensor and how it changes over temperature
double S = S0 * (1 + a1 * (Tdie - Tref) + a2 * Math.Pow((Tdie - Tref), 2));
// offset voltage that arises because of the slight self-heating of the TMP006 chip
double Vos = b0 + b1 * (Tdie - Tref) + b2 * Math.Pow((Tdie - Tref), 2);
// models the Seebeck coefficients of the thermopile and how these coefficients change over temperature.
double fObj = (Vobj2 - Vos) + c2 * Math.Pow((Vobj2 - Vos), 2);
// computes the radiant transfer of IR energy between the target object and the TMP006 chip
// and the conducted heat in the thermopile in the TMP006.
double tObj = Math.Pow(Math.Pow(Tdie, 4) + (fObj / S), .25);
// back to celcius
measurement.ObjectTemperature = (tObj - toKelvin);
}
else
{
const double SCALE_LSB = 0.03125;
int it;
it = (int)((objTemp) >> 2);
measurement.ObjectTemperature = (double)it * SCALE_LSB;
it = (int)((dieTemp) >> 2);
measurement.DieTemperature = (double)it * SCALE_LSB;
}
OnIRTemperatureMeasurementValueChanged(new IRTemperatureMeasurementEventArgs(measurement, eventArgs.Timestamp));
}
}
}
}
}
