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Oct 31, 2017
Merged

Fix up the docs. #1

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51 changes: 28 additions & 23 deletions adafruit_bme280.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
"""
`adafruit_bmp280`
`adafruit_bme280`
====================================================

CircuitPython driver from BME280 Temperature, Humidity and Barometic Pressure sensor
Expand Down Expand Up @@ -63,6 +63,7 @@
_BME280_HUMIDITY_MAX = const(100)

class Adafruit_BME280:
"""Driver from BME280 Temperature, Humidity and Barometic Pressure sensor"""
def __init__(self):
"""Check the BME280 was found, read the coefficients and enable the sensor for continuous reads"""
# Check device ID.
Expand All @@ -73,16 +74,17 @@ def __init__(self):
time.sleep(0.5)
self._read_coefficients()
self.seaLevelhPa = 1013.25
"""Pressure in hectoPascals at sea level. Used to calibrate `altitude`."""
self._write_register_byte(_BME280_REGISTER_CTRL_HUM, 0x03) # turn on humidity oversample 16x

@property
def temperature(self):
"""Gets the compensated temperature in degrees celsius."""
"""The compensated temperature in degrees celsius."""
# perform one measurement
self._write_register_byte(_BME280_REGISTER_CTRL_MEAS, 0xFE) # high res, forced mode

# Wait for conversion to complete
while (self._read_byte(_BME280_REGISTER_STATUS) & 0x08):
while (self._read_byte(_BME280_REGISTER_STATUS) & 0x08):
time.sleep(0.002)
UT = self._read24(_BME280_REGISTER_TEMPDATA) / 16 # lowest 4 bits get dropped
#print("raw temp: ", UT)
Expand All @@ -95,16 +97,16 @@ def temperature(self):

self.t_fine = int(var1 + var2)
#print("t_fine: ", self.t_fine)

temp = (var1 + var2) / 5120.0
return temp

@property
def pressure(self):
"""Gets the compensated pressure in hectoPascals."""
"""The compensated pressure in hectoPascals."""
self.temperature # force read of t_fine
# Algorithm from the BME280 driver https://github.com/BoschSensortec/BME280_driver/blob/master/bme280.c

# Algorithm from the BME280 driver https://github.com/BoschSensortec/BME280_driver/blob/master/bme280.c
adc = self._read24(_BME280_REGISTER_PRESSUREDATA) / 16 # lowest 4 bits get dropped
var1 = float(self.t_fine) / 2.0 - 64000.0
var2 = var1 * var1 * self.dig_P6 / 32768.0
Expand All @@ -123,14 +125,15 @@ def pressure(self):
p = p + (var1 + var2 + self.dig_P7) / 16.0

p /= 100
if (p < _BME280_PRESSURE_MIN_HPA): return _BME280_PRESSURE_MIN_HPA
if (p > _BME280_PRESSURE_MAX_HPA): return _BME280_PRESSURE_MAX_HPA
if (p < _BME280_PRESSURE_MIN_HPA): return _BME280_PRESSURE_MIN_HPA
if (p > _BME280_PRESSURE_MAX_HPA): return _BME280_PRESSURE_MAX_HPA
return p
else:
return _BME280_PRESSURE_MIN_HPA

@property
def humidity(self):
"""The relative humidity in RH %"""
self.temperature # force read of t_fine
hum = self._read_register(_BME280_REGISTER_HUMIDDATA, 2)
#print("Humidity data: ", hum)
Expand All @@ -140,27 +143,29 @@ def humidity(self):
# Algorithm from the BME280 driver https://github.com/BoschSensortec/BME280_driver/blob/master/bme280.c
var1 = float(self.t_fine) - 76800.0
#print("var1 ", var1)
var2 = (self.dig_H4 * 64.0 + (self.dig_H5 / 16384.0) * var1)
var2 = (self.dig_H4 * 64.0 + (self.dig_H5 / 16384.0) * var1)
#print("var2 ",var2)
var3 = adc - var2
var3 = adc - var2
#print("var3 ",var3)
var4 = self.dig_H2 / 65536.0
var4 = self.dig_H2 / 65536.0
#print("var4 ",var4)
var5 = (1.0 + (self.dig_H3 / 67108864.0) * var1)
var5 = (1.0 + (self.dig_H3 / 67108864.0) * var1)
#print("var5 ",var5)
var6 = 1.0 + (self.dig_H6 / 67108864.0) * var1 * var5
var6 = 1.0 + (self.dig_H6 / 67108864.0) * var1 * var5
#print("var6 ",var6)
var6 = var3 * var4 * (var5 * var6)
humidity = var6 * (1.0 - self.dig_H1 * var6 / 524288.0)
var6 = var3 * var4 * (var5 * var6)
humidity = var6 * (1.0 - self.dig_H1 * var6 / 524288.0)

if (humidity > _BME280_HUMIDITY_MAX): return _BME280_HUMIDITY_MAX
if (humidity < _BME280_HUMIDITY_MIN): return _BME280_HUMIDITY_MIN
if (humidity > _BME280_HUMIDITY_MAX):
return _BME280_HUMIDITY_MAX
if (humidity < _BME280_HUMIDITY_MIN):
return _BME280_HUMIDITY_MIN
# else...
return humidity

@property
def altitude(self):
"""calculate the altitude based on the sea level pressure (seaLevelhPa) - which you must enter ahead of time)"""
"""The altitude based on current `pressure` versus the sea level pressure (`seaLevelhPa`) - which you must enter ahead of time)"""
p = self.pressure # in Si units for hPascal
return 44330 * (1.0 - math.pow(p / self.seaLevelhPa, 0.1903));

Expand All @@ -185,7 +190,7 @@ def _read_coefficients(self):
#print("%d %d %d" % (self.dig_P7, self.dig_P8, self.dig_P9))
#print("%d %d %d" % (self.dig_H1, self.dig_H2, self.dig_H3))
#print("%d %d %d" % (self.dig_H4, self.dig_H5, self.dig_H6))

def _read_byte(self, register):
"""Read a byte register value and return it"""
return self._read_register(register, 1)[0]
Expand All @@ -197,7 +202,7 @@ def _read24(self, register):
ret *= 256.0
ret += float(b & 0xFF)
return ret

class Adafruit_BME280_I2C(Adafruit_BME280):
def __init__(self, i2c, address=_BME280_ADDRESS):
import adafruit_bus_device.i2c_device as i2c_device
Expand Down
3 changes: 3 additions & 0 deletions conf.py
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,9 @@
'sphinx.ext.viewcode',
]

# API docs fix
autodoc_mock_imports = ['micropython']

intersphinx_mapping = {'python': ('https://docs.python.org/3.4', None),'BusDevice': ('https://circuitpython.readthedocs.io/projects/bus_device/en/latest/', None),'CircuitPython': ('https://circuitpython.readthedocs.io/en/latest/', None)}

# Add any paths that contain templates here, relative to this directory.
Expand Down