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Use floating point precision for measurement compensations to yield sensor resolution

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According to the datasheet the resolution delivered by the sensor is better
than 1 degree Celsius, 1 Pascal, 1 percent relative humidity etc. The user
should have the possibility to get floating point precision and figure out
what the measurement accuracy allows given their settings.
This commit is contained in:
cn 2018-12-07 11:34:00 +01:00 committed by Christian Nicolai
parent db02dd0d65
commit 6442510ab0
1 changed files with 39 additions and 39 deletions
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78
library/bme680/__init__.py
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@ -315,68 +315,68 @@ class BME680(BME680Data):
def _calc_temperature(self, temperature_adc): def _calc_temperature(self, temperature_adc):
"""Convert the raw temperature to degrees C using calibration_data.""" """Convert the raw temperature to degrees C using calibration_data."""
var1 = (temperature_adc >> 3) - (self.calibration_data.par_t1 << 1) var1 = (temperature_adc / 8.0) - (self.calibration_data.par_t1 * 2.0)
var2 = (var1 * self.calibration_data.par_t2) >> 11 var2 = (var1 * self.calibration_data.par_t2) / 2048.0
var3 = ((var1 >> 1) * (var1 >> 1)) >> 12 var3 = ((var1 / 2.0) * (var1 / 2.0)) / 4096.0
var3 = ((var3) * (self.calibration_data.par_t3 << 4)) >> 14 var3 = ((var3) * (self.calibration_data.par_t3 * 16.0)) / 16384.0
# Save teperature data for pressure calculations # Save teperature data for pressure calculations
self.calibration_data.t_fine = (var2 + var3) + self.offset_temp_in_t_fine self.calibration_data.t_fine = (var2 + var3) + self.offset_temp_in_t_fine
calc_temp = (((self.calibration_data.t_fine * 5) + 128) >> 8) calc_temp = (((self.calibration_data.t_fine * 5.0) + 128.0) / 256.0)
return calc_temp return calc_temp
def _calc_pressure(self, pressure_adc): def _calc_pressure(self, pressure_adc):
"""Convert the raw pressure using calibration data.""" """Convert the raw pressure using calibration data."""
var1 = ((self.calibration_data.t_fine) >> 1) - 64000 var1 = (self.calibration_data.t_fine / 2.0) - 64000.0
var2 = ((((var1 >> 2) * (var1 >> 2)) >> 11) * var2 = ((((var1 / 4.0) * (var1 / 4.0)) / 2048.0) *
self.calibration_data.par_p6) >> 2 self.calibration_data.par_p6) / 4.0
var2 = var2 + ((var1 * self.calibration_data.par_p5) << 1) var2 = var2 + ((var1 * self.calibration_data.par_p5) * 2.0)
var2 = (var2 >> 2) + (self.calibration_data.par_p4 << 16) var2 = (var2 / 4.0) + (self.calibration_data.par_p4 * 65536.0)
var1 = (((((var1 >> 2) * (var1 >> 2)) >> 13) * var1 = (((((var1 / 4.0) * (var1 / 4.0)) / 8192.0) *
((self.calibration_data.par_p3 << 5)) >> 3) + ((self.calibration_data.par_p3 * 32.0)) / 8.0) +
((self.calibration_data.par_p2 * var1) >> 1)) ((self.calibration_data.par_p2 * var1) / 2.0))
var1 = var1 >> 18 var1 = var1 / 262144.0
var1 = ((32768 + var1) * self.calibration_data.par_p1) >> 15 var1 = ((32768.0 + var1) * self.calibration_data.par_p1) / 32768.0
calc_pressure = 1048576 - pressure_adc calc_pressure = 1048576.0 - pressure_adc
calc_pressure = ((calc_pressure - (var2 >> 12)) * (3125)) calc_pressure = ((calc_pressure - (var2 / 4096.0)) * (3125.0))
if calc_pressure >= (1 << 31): if calc_pressure >= (1 << 31):
calc_pressure = ((calc_pressure // var1) << 1) calc_pressure = ((calc_pressure / var1) * 2.0)
else: else:
calc_pressure = ((calc_pressure << 1) // var1) calc_pressure = ((calc_pressure * 2.0) / var1)
var1 = (self.calibration_data.par_p9 * (((calc_pressure >> 3) * var1 = (self.calibration_data.par_p9 * (((calc_pressure / 8.0) *
(calc_pressure >> 3)) >> 13)) >> 12 (calc_pressure / 8.0)) / 8192.0)) / 4096.0
var2 = ((calc_pressure >> 2) * var2 = ((calc_pressure / 4.0) *
self.calibration_data.par_p8) >> 13 self.calibration_data.par_p8) / 8192.0
var3 = ((calc_pressure >> 8) * (calc_pressure >> 8) * var3 = ((calc_pressure / 256.0) * (calc_pressure / 256.0) *
(calc_pressure >> 8) * (calc_pressure / 256.0) *
self.calibration_data.par_p10) >> 17 self.calibration_data.par_p10) / 131072.0
calc_pressure = (calc_pressure) + ((var1 + var2 + var3 + calc_pressure = (calc_pressure) + ((var1 + var2 + var3 +
(self.calibration_data.par_p7 << 7)) >> 4) (self.calibration_data.par_p7 * 128.0)) / 16.0)
return calc_pressure return calc_pressure
def _calc_humidity(self, humidity_adc): def _calc_humidity(self, humidity_adc):
"""Convert the raw humidity using calibration data.""" """Convert the raw humidity using calibration data."""
temp_scaled = ((self.calibration_data.t_fine * 5) + 128) >> 8 temp_scaled = ((self.calibration_data.t_fine * 5.0) + 128.0) / 256.0
var1 = (humidity_adc - ((self.calibration_data.par_h1 * 16))) -\ var1 = (humidity_adc - ((self.calibration_data.par_h1 * 16.0))) -\
(((temp_scaled * self.calibration_data.par_h3) // (100)) >> 1) (((temp_scaled * self.calibration_data.par_h3) / (100.0)) / 2.0)
var2 = (self.calibration_data.par_h2 * var2 = (self.calibration_data.par_h2 *
(((temp_scaled * self.calibration_data.par_h4) // (100)) + (((temp_scaled * self.calibration_data.par_h4) / (100.0)) +
(((temp_scaled * ((temp_scaled * self.calibration_data.par_h5) // (100))) >> 6) // (((temp_scaled * ((temp_scaled * self.calibration_data.par_h5) / (100.0))) / 64.0) /
(100)) + (1 * 16384))) >> 10 (100.0)) + (1.0 * 16384.0))) / 1024.0
var3 = var1 * var2 var3 = var1 * var2
var4 = self.calibration_data.par_h6 << 7 var4 = self.calibration_data.par_h6 * 128.0
var4 = ((var4) + ((temp_scaled * self.calibration_data.par_h7) // (100))) >> 4 var4 = ((var4) + ((temp_scaled * self.calibration_data.par_h7) / (100.0))) / 16.0
var5 = ((var3 >> 14) * (var3 >> 14)) >> 10 var5 = ((var3 / 16384.0) * (var3 / 16384.0)) / 1024.0
var6 = (var4 * var5) >> 1 var6 = (var4 * var5) / 2.0
calc_hum = (((var3 + var6) >> 10) * (1000)) >> 12 calc_hum = (((var3 + var6) / 1024.0) * (1000.0)) / 4096.0
return min(max(calc_hum, 0), 100000) return min(max(calc_hum, 0.0), 100000.0)
def _calc_gas_resistance(self, gas_res_adc, gas_range): def _calc_gas_resistance(self, gas_res_adc, gas_range):
"""Convert the raw gas resistance using calibration data.""" """Convert the raw gas resistance using calibration data."""