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