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Update for BME688 #43

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Merged
merged 1 commit into from
Dec 8, 2021
Merged

Update for BME688 #43

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41 changes: 30 additions & 11 deletions adafruit_bme680.py
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@
_BME680_CHIPID = const(0x61)

_BME680_REG_CHIPID = const(0xD0)
_BME68X_REG_VARIANT = const(0xF0)
_BME680_BME680_COEFF_ADDR1 = const(0x89)
_BME680_BME680_COEFF_ADDR2 = const(0xE1)
_BME680_BME680_RES_HEAT_0 = const(0x5A)
Expand Down Expand Up @@ -135,6 +136,9 @@ def __init__(self, *, refresh_rate=10):
if chip_id != _BME680_CHIPID:
raise RuntimeError("Failed to find BME680! Chip ID 0x%x" % chip_id)

# Get variant
self._chip_variant = self._read_byte(_BME68X_REG_VARIANT)

self._read_calibration()

# set up heater
Expand Down Expand Up @@ -297,12 +301,21 @@ def altitude(self):
def gas(self):
"""The gas resistance in ohms"""
self._perform_reading()
var1 = (
(1340 + (5 * self._sw_err)) * (_LOOKUP_TABLE_1[self._gas_range])
) / 65536
var2 = ((self._adc_gas * 32768) - 16777216) + var1
var3 = (_LOOKUP_TABLE_2[self._gas_range] * var1) / 512
calc_gas_res = (var3 + (var2 / 2)) / var2
if self._chip_variant == 0x01:
# taken from https://github.com/BoschSensortec/BME68x-Sensor-API
var1 = 262144 >> self._gas_range
var2 = self._adc_gas - 512
var2 *= 3
var2 = 4096 + var2
calc_gas_res = (1000 * var1) / var2
calc_gas_res = calc_gas_res * 100
else:
var1 = (
(1340 + (5 * self._sw_err)) * (_LOOKUP_TABLE_1[self._gas_range])
) / 65536
var2 = ((self._adc_gas * 32768) - 16777216) + var1
var3 = (_LOOKUP_TABLE_2[self._gas_range] * var1) / 512
calc_gas_res = (var3 + (var2 / 2)) / var2
return int(calc_gas_res)

def _perform_reading(self):
Expand All @@ -321,23 +334,29 @@ def _perform_reading(self):
# turn on humidity oversample
self._write(_BME680_REG_CTRL_HUM, [self._humidity_oversample])
# gas measurements enabled
self._write(_BME680_REG_CTRL_GAS, [_BME680_RUNGAS])

if self._chip_variant == 0x01:
self._write(_BME680_REG_CTRL_GAS, [_BME680_RUNGAS << 1])
else:
self._write(_BME680_REG_CTRL_GAS, [_BME680_RUNGAS])
ctrl = self._read_byte(_BME680_REG_CTRL_MEAS)
ctrl = (ctrl & 0xFC) | 0x01 # enable single shot!
self._write(_BME680_REG_CTRL_MEAS, [ctrl])
new_data = False
while not new_data:
data = self._read(_BME680_REG_MEAS_STATUS, 15)
data = self._read(_BME680_REG_MEAS_STATUS, 17)
new_data = data[0] & 0x80 != 0
time.sleep(0.005)
self._last_reading = time.monotonic()

self._adc_pres = _read24(data[2:5]) / 16
self._adc_temp = _read24(data[5:8]) / 16
self._adc_hum = struct.unpack(">H", bytes(data[8:10]))[0]
self._adc_gas = int(struct.unpack(">H", bytes(data[13:15]))[0] / 64)
self._gas_range = data[14] & 0x0F
if self._chip_variant == 0x01:
self._adc_gas = int(struct.unpack(">H", bytes(data[15:17]))[0] / 64)
self._gas_range = data[16] & 0x0F
else:
self._adc_gas = int(struct.unpack(">H", bytes(data[13:15]))[0] / 64)
self._gas_range = data[14] & 0x0F

var1 = (self._adc_temp / 8) - (self._temp_calibration[0] * 2)
var2 = (var1 * self._temp_calibration[1]) / 2048
Expand Down