286 lines
9.8 KiB
Python
286 lines
9.8 KiB
Python
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from machine import I2C
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import time
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# BME280 default address.
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BME280_I2CADDR = 0x76
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# Operating Modes
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BME280_OSAMPLE_1 = 1
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BME280_OSAMPLE_2 = 2
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BME280_OSAMPLE_4 = 3
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BME280_OSAMPLE_8 = 4
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BME280_OSAMPLE_16 = 5
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# BME280 Registers
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BME280_REGISTER_DIG_T1 = 0x88 # Trimming parameter registers
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BME280_REGISTER_DIG_T2 = 0x8A
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BME280_REGISTER_DIG_T3 = 0x8C
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BME280_REGISTER_DIG_P1 = 0x8E
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BME280_REGISTER_DIG_P2 = 0x90
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BME280_REGISTER_DIG_P3 = 0x92
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BME280_REGISTER_DIG_P4 = 0x94
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BME280_REGISTER_DIG_P5 = 0x96
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BME280_REGISTER_DIG_P6 = 0x98
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BME280_REGISTER_DIG_P7 = 0x9A
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BME280_REGISTER_DIG_P8 = 0x9C
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BME280_REGISTER_DIG_P9 = 0x9E
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BME280_REGISTER_DIG_H1 = 0xA1
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BME280_REGISTER_DIG_H2 = 0xE1
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BME280_REGISTER_DIG_H3 = 0xE3
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BME280_REGISTER_DIG_H4 = 0xE4
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BME280_REGISTER_DIG_H5 = 0xE5
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BME280_REGISTER_DIG_H6 = 0xE6
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BME280_REGISTER_DIG_H7 = 0xE7
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BME280_REGISTER_CHIPID = 0xD0
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BME280_REGISTER_VERSION = 0xD1
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BME280_REGISTER_SOFTRESET = 0xE0
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BME280_REGISTER_CONTROL_HUM = 0xF2
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BME280_REGISTER_CONTROL = 0xF4
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BME280_REGISTER_CONFIG = 0xF5
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BME280_REGISTER_PRESSURE_DATA = 0xF7
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BME280_REGISTER_TEMP_DATA = 0xFA
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BME280_REGISTER_HUMIDITY_DATA = 0xFD
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class Device:
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"""Class for communicating with an I2C device.
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Allows reading and writing 8-bit, 16-bit, and byte array values to
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registers on the device."""
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def __init__(self, address, i2c):
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"""Create an instance of the I2C device at the specified address using
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the specified I2C interface object."""
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self._address = address
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self._i2c = i2c
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def writeRaw8(self, value):
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"""Write an 8-bit value on the bus (without register)."""
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value = value & 0xFF
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self._i2c.writeto(self._address, value)
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def write8(self, register, value):
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"""Write an 8-bit value to the specified register."""
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b=bytearray(1)
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b[0]=value & 0xFF
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self._i2c.writeto_mem(self._address, register, b)
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def write16(self, register, value):
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"""Write a 16-bit value to the specified register."""
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value = value & 0xFFFF
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b=bytearray(2)
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b[0]= value & 0xFF
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b[1]= (value>>8) & 0xFF
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self.i2c.writeto_mem(self._address, register, value)
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def readRaw8(self):
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"""Read an 8-bit value on the bus (without register)."""
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return int.from_bytes(self._i2c.readfrom(self._address, 1),'little') & 0xFF
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def readU8(self, register):
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"""Read an unsigned byte from the specified register."""
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return int.from_bytes(
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self._i2c.readfrom_mem(self._address, register, 1),'little') & 0xFF
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def readS8(self, register):
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"""Read a signed byte from the specified register."""
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result = self.readU8(register)
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if result > 127:
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result -= 256
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return result
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def readU16(self, register, little_endian=True):
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"""Read an unsigned 16-bit value from the specified register, with the
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specified endianness (default little endian, or least significant byte
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first)."""
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result = int.from_bytes(
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self._i2c.readfrom_mem(self._address, register, 2),'little') & 0xFFFF
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if not little_endian:
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result = ((result << 8) & 0xFF00) + (result >> 8)
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return result
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def readS16(self, register, little_endian=True):
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"""Read a signed 16-bit value from the specified register, with the
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specified endianness (default little endian, or least significant byte
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first)."""
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result = self.readU16(register, little_endian)
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if result > 32767:
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result -= 65536
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return result
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def readU16LE(self, register):
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"""Read an unsigned 16-bit value from the specified register, in little
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endian byte order."""
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return self.readU16(register, little_endian=True)
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def readU16BE(self, register):
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"""Read an unsigned 16-bit value from the specified register, in big
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endian byte order."""
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return self.readU16(register, little_endian=False)
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def readS16LE(self, register):
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"""Read a signed 16-bit value from the specified register, in little
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endian byte order."""
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return self.readS16(register, little_endian=True)
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def readS16BE(self, register):
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"""Read a signed 16-bit value from the specified register, in big
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endian byte order."""
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return self.readS16(register, little_endian=False)
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class BME280:
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def __init__(self, mode=BME280_OSAMPLE_1, address=BME280_I2CADDR, i2c=None,
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**kwargs):
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# Check that mode is valid.
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if mode not in [BME280_OSAMPLE_1, BME280_OSAMPLE_2, BME280_OSAMPLE_4,
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BME280_OSAMPLE_8, BME280_OSAMPLE_16]:
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raise ValueError(
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'Unexpected mode value {0}. Set mode to one of '
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'BME280_ULTRALOWPOWER, BME280_STANDARD, BME280_HIGHRES, or '
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'BME280_ULTRAHIGHRES'.format(mode))
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self._mode = mode
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# Create I2C device.
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if i2c is None:
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raise ValueError('An I2C object is required.')
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self._device = Device(address, i2c)
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# Load calibration values.
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self._load_calibration()
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self._device.write8(BME280_REGISTER_CONTROL, 0x3F)
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self.t_fine = 0
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def _load_calibration(self):
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self.dig_T1 = self._device.readU16LE(BME280_REGISTER_DIG_T1)
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self.dig_T2 = self._device.readS16LE(BME280_REGISTER_DIG_T2)
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self.dig_T3 = self._device.readS16LE(BME280_REGISTER_DIG_T3)
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self.dig_P1 = self._device.readU16LE(BME280_REGISTER_DIG_P1)
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self.dig_P2 = self._device.readS16LE(BME280_REGISTER_DIG_P2)
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self.dig_P3 = self._device.readS16LE(BME280_REGISTER_DIG_P3)
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self.dig_P4 = self._device.readS16LE(BME280_REGISTER_DIG_P4)
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self.dig_P5 = self._device.readS16LE(BME280_REGISTER_DIG_P5)
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self.dig_P6 = self._device.readS16LE(BME280_REGISTER_DIG_P6)
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self.dig_P7 = self._device.readS16LE(BME280_REGISTER_DIG_P7)
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self.dig_P8 = self._device.readS16LE(BME280_REGISTER_DIG_P8)
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self.dig_P9 = self._device.readS16LE(BME280_REGISTER_DIG_P9)
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self.dig_H1 = self._device.readU8(BME280_REGISTER_DIG_H1)
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self.dig_H2 = self._device.readS16LE(BME280_REGISTER_DIG_H2)
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self.dig_H3 = self._device.readU8(BME280_REGISTER_DIG_H3)
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self.dig_H6 = self._device.readS8(BME280_REGISTER_DIG_H7)
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h4 = self._device.readS8(BME280_REGISTER_DIG_H4)
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h4 = (h4 << 24) >> 20
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self.dig_H4 = h4 | (self._device.readU8(BME280_REGISTER_DIG_H5) & 0x0F)
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h5 = self._device.readS8(BME280_REGISTER_DIG_H6)
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h5 = (h5 << 24) >> 20
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self.dig_H5 = h5 | (
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self._device.readU8(BME280_REGISTER_DIG_H5) >> 4 & 0x0F)
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def read_raw_temp(self):
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"""Reads the raw (uncompensated) temperature from the sensor."""
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meas = self._mode
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self._device.write8(BME280_REGISTER_CONTROL_HUM, meas)
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meas = self._mode << 5 | self._mode << 2 | 1
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self._device.write8(BME280_REGISTER_CONTROL, meas)
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sleep_time = 1250 + 2300 * (1 << self._mode)
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sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
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sleep_time = sleep_time + 2300 * (1 << self._mode) + 575
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time.sleep_us(sleep_time) # Wait the required time
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msb = self._device.readU8(BME280_REGISTER_TEMP_DATA)
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lsb = self._device.readU8(BME280_REGISTER_TEMP_DATA + 1)
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xlsb = self._device.readU8(BME280_REGISTER_TEMP_DATA + 2)
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raw = ((msb << 16) | (lsb << 8) | xlsb) >> 4
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return raw
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def read_raw_pressure(self):
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"""Reads the raw (uncompensated) pressure level from the sensor."""
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"""Assumes that the temperature has already been read """
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"""i.e. that enough delay has been provided"""
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msb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA)
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lsb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA + 1)
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xlsb = self._device.readU8(BME280_REGISTER_PRESSURE_DATA + 2)
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raw = ((msb << 16) | (lsb << 8) | xlsb) >> 4
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return raw
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def read_raw_humidity(self):
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"""Assumes that the temperature has already been read """
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"""i.e. that enough delay has been provided"""
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msb = self._device.readU8(BME280_REGISTER_HUMIDITY_DATA)
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lsb = self._device.readU8(BME280_REGISTER_HUMIDITY_DATA + 1)
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raw = (msb << 8) | lsb
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return raw
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def read_temperature(self):
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"""Get the compensated temperature in 0.01 of a degree celsius."""
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adc = self.read_raw_temp()
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var1 = ((adc >> 3) - (self.dig_T1 << 1)) * (self.dig_T2 >> 11)
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var2 = ((
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(((adc >> 4) - self.dig_T1) * ((adc >> 4) - self.dig_T1)) >> 12) *
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self.dig_T3) >> 14
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self.t_fine = var1 + var2
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return (self.t_fine * 5 + 128) >> 8
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def read_pressure(self):
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"""Gets the compensated pressure in Pascals."""
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adc = self.read_raw_pressure()
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var1 = self.t_fine - 128000
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var2 = var1 * var1 * self.dig_P6
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var2 = var2 + ((var1 * self.dig_P5) << 17)
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var2 = var2 + (self.dig_P4 << 35)
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var1 = (((var1 * var1 * self.dig_P3) >> 8) +
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((var1 * self.dig_P2) >> 12))
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var1 = (((1 << 47) + var1) * self.dig_P1) >> 33
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if var1 == 0:
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return 0
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p = 1048576 - adc
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p = (((p << 31) - var2) * 3125) // var1
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var1 = (self.dig_P9 * (p >> 13) * (p >> 13)) >> 25
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var2 = (self.dig_P8 * p) >> 19
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return ((p + var1 + var2) >> 8) + (self.dig_P7 << 4)
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def read_humidity(self):
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adc = self.read_raw_humidity()
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# print 'Raw humidity = {0:d}'.format (adc)
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h = self.t_fine - 76800
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h = (((((adc << 14) - (self.dig_H4 << 20) - (self.dig_H5 * h)) +
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16384) >> 15) * (((((((h * self.dig_H6) >> 10) * (((h *
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self.dig_H3) >> 11) + 32768)) >> 10) + 2097152) *
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self.dig_H2 + 8192) >> 14))
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h = h - (((((h >> 15) * (h >> 15)) >> 7) * self.dig_H1) >> 4)
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h = 0 if h < 0 else h
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h = 419430400 if h > 419430400 else h
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return h >> 12
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@property
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def temperature(self):
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"Return the temperature in degrees."
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t = self.read_temperature()
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ti = t // 100
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td = t - ti * 100
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return "{}.{:02d}C".format(ti, td)
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@property
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def pressure(self):
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"Return the temperature in hPa."
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p = self.read_pressure() // 256
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pi = p // 100
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pd = p - pi * 100
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return "{}.{:02d}hPa".format(pi, pd)
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@property
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def humidity(self):
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"Return the humidity in percent."
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h = self.read_humidity()
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hi = h // 1024
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hd = h * 100 // 1024 - hi * 100
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return "{}.{:02d}%".format(hi, hd)
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