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OP-1793 - Filter temperature to reduce the noise injected into pressure measuremenent.

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This commit is contained in:
Alessio Morale 2015-03-18 05:29:39 +01:00
parent 8eaf7f9918
commit bcffde5465
1 changed files with 11 additions and 5 deletions
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16
flight/pios/common/pios_ms5611.c
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@ -72,6 +72,7 @@ static uint32_t RawTemperature;
static uint32_t RawPressure;
static int64_t Pressure;
static int64_t Temperature;
static int64_t FilteredTemperature = INT32_MIN;
static int32_t lastConversionStart;
static uint32_t conversionDelayMs;
@ -247,6 +248,11 @@ int32_t PIOS_MS5611_ReadADC(void)
// Actual temperature (-40…85°C with 0.01°C resolution)
// TEMP = 20°C + dT * TEMPSENS = 2000 + dT * C6 / 2^23
Temperature = 2000l + ((deltaTemp * CalibData.C[5]) / POW2(23));
if(FilteredTemperature != INT32_MIN){
FilteredTemperature = (FilteredTemperature * 9 + Temperature) / 10;
} else {
FilteredTemperature = Temperature;
}
} else {
int64_t Offset;
int64_t Sens;
@ -259,21 +265,21 @@ int32_t PIOS_MS5611_ReadADC(void)
return -2;
}
// check if temperature is less than 20°C
if (Temperature < 2000) {
if (FilteredTemperature < 2000) {
// Apply compensation
// T2 = dT^2 / 2^31
// OFF2 = 5 ⋅ (TEMP – 2000)^2/2
// SENS2 = 5 ⋅ (TEMP – 2000)^2/2^2
int64_t tcorr = (Temperature - 2000) * (Temperature - 2000);
int64_t tcorr = (FilteredTemperature - 2000) * (FilteredTemperature - 2000);
Offset2 = (5 * tcorr) / 2;
Sens2 = (5 * tcorr) / 4;
compensation_t2 = (deltaTemp * deltaTemp) >> 31;
// Apply the "Very low temperature compensation" when temp is less than -15°C
if (Temperature < -1500) {
if (FilteredTemperature < -1500) {
// OFF2 = OFF2 + 7 ⋅ (TEMP + 1500)^2
// SENS2 = SENS2 + 11 ⋅ (TEMP + 1500)^2 / 2
int64_t tcorr2 = (Temperature + 1500) * (Temperature + 1500);
int64_t tcorr2 = (FilteredTemperature + 1500) * (FilteredTemperature + 1500);
Offset2 += 7 * tcorr2;
Sens2 += (11 * tcorr2) / 2;
}
@ -302,7 +308,7 @@ int32_t PIOS_MS5611_ReadADC(void)
static float PIOS_MS5611_GetTemperature(void)
{
// Apply the second order low and very low temperature compensation offset
return ((float)(Temperature - compensation_t2)) / 100.0f;
return ((float)(FilteredTemperature - compensation_t2)) / 100.0f;
}
/**