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BMP280.py
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from micropython import const
BMP280_I2C_ADDRESS = const(0x77)
#Registers value
BMP280_ID_Value = const(0x58)
BMP280_RESET_VALUE = const(0xB6)
# BMP280 Registers definition
BMP280_TEMP_XLSB_REG = const(0xFC)
BMP280_TEMP_LSB_REG = const(0xFB)
BMP280_TEMP_MSB_REG = const(0xFA)
BMP280_PRESS_XLSB_REG = const(0xF9)
BMP280_PRESS_LSB_REG = const(0xF8)
BMP280_PRESS_MSB_REG = const(0xF7)
BMP280_CONFIG_REG = const(0xF5)
BMP280_CTRL_MEAS_REG = const(0xF4)
BMP280_STATUS_REG = const(0xF3)
BMP280_RESET_REG = const(0xE0)
BMP280_ID_REG = const(0xD0)
#calibration parameters
BMP280_DIG_T1_LSB_REG = const(0x88)
BMP280_DIG_T1_MSB_REG = const(0x89)
BMP280_DIG_T2_LSB_REG = const(0x8A)
BMP280_DIG_T2_MSB_REG = const(0x8B)
BMP280_DIG_T3_LSB_REG = const(0x8C)
BMP280_DIG_T3_MSB_REG = const(0x8D)
BMP280_DIG_P1_LSB_REG = const(0x8E)
BMP280_DIG_P1_MSB_REG = const(0x8F)
BMP280_DIG_P2_LSB_REG = const(0x90)
BMP280_DIG_P2_MSB_REG = const(0x91)
BMP280_DIG_P3_LSB_REG = const(0x92)
BMP280_DIG_P3_MSB_REG = const(0x93)
BMP280_DIG_P4_LSB_REG = const(0x94)
BMP280_DIG_P4_MSB_REG = const(0x95)
BMP280_DIG_P5_LSB_REG = const(0x96)
BMP280_DIG_P5_MSB_REG = const(0x97)
BMP280_DIG_P6_LSB_REG = const(0x98)
BMP280_DIG_P6_MSB_REG = const(0x99)
BMP280_DIG_P7_LSB_REG = const(0x9A)
BMP280_DIG_P7_MSB_REG = const(0x9B)
BMP280_DIG_P8_LSB_REG = const(0x9C)
BMP280_DIG_P8_MSB_REG = const(0x9D)
BMP280_DIG_P9_LSB_REG = const(0x9E)
BMP280_DIG_P9_MSB_REG = const(0x9F)
ELEVATION = const(4)
class BMP280():
def __init__(self, _i2c):
self.i2c = _i2c
self.i2c_address = BMP280_I2C_ADDRESS
self.t_fine = 0
if (self.read_byte(BMP280_ID_REG) == BMP280_ID_Value):
self.load_calibration_data()
self.write_byte(BMP280_CTRL_MEAS_REG, 0xFF)
self.write_byte(BMP280_CONFIG_REG, 0x14)
else:
print("BMP280 error!")
def write_byte(self, reg, value):
if not type(value) is bytearray:
value = bytearray([value])
self.i2c.writeto_mem(self.i2c_address, reg, value)
def read_byte(self, reg):
retval = self.i2c.readfrom_mem(self.i2c_address, reg, 1)
return retval[0]
def read_word(self, reg):
value = self.i2c.readfrom_mem(self.i2c_address, reg, 2)
return ((value[1] << 8) | value[0])
def read_signed_word(self, reg):
RES = self.read_word(reg)
if (RES > 32767):
RES -= 65536
return RES
def load_calibration_data(self):
# Temperature Calibration Parameters
self.dig_T1 = self.read_word(BMP280_DIG_T1_LSB_REG)
self.dig_T2 = self.read_signed_word(BMP280_DIG_T2_LSB_REG)
self.dig_T3 = self.read_signed_word(BMP280_DIG_T3_LSB_REG)
# Barometeric Pressure Calibration Parameters
self.dig_P1 = self.read_word(BMP280_DIG_P1_LSB_REG)
self.dig_P2 = self.read_signed_word(BMP280_DIG_P2_LSB_REG)
self.dig_P3 = self.read_signed_word(BMP280_DIG_P3_LSB_REG)
self.dig_P4 = self.read_signed_word(BMP280_DIG_P4_LSB_REG)
self.dig_P5 = self.read_signed_word(BMP280_DIG_P5_LSB_REG)
self.dig_P6 = self.read_signed_word(BMP280_DIG_P6_LSB_REG)
self.dig_P7 = self.read_signed_word(BMP280_DIG_P7_LSB_REG)
self.dig_P8 = self.read_signed_word(BMP280_DIG_P8_LSB_REG)
self.dig_P9 = self.read_signed_word(BMP280_DIG_P9_LSB_REG)
def compensate_temperature(self, adc_T):
var1 = ((adc_T) / 16384.0 - (self.dig_T1) / 1024.0) * (self.dig_T2)
var2 = (((adc_T) / 131072.0 - (self.dig_T1) / 8192.0) * ((adc_T) / 131072.0 - (self.dig_T1) / 8192.0)) * (self.dig_T3)
self.t_fine = var1 + var2
temperature = (var1 + var2) / 5120.0
return temperature
def compensate_pressure(self,adc_P):
var1 = (self.t_fine / 2.0) - 64000.0
var2 = var1 * var1 * (self.dig_P6) / 32768.0
var2 = var2 + var1 * (self.dig_P5) * 2.0
var2 = (var2 / 4.0) + ((self.dig_P4) * 65536.0)
var1 = ((self.dig_P3) * var1 * var1 / 524288.0 + (self.dig_P2) * var1) / 524288.0
var1 = (1.0 + var1 / 32768.0) * (self.dig_P1)
if var1 == 0.0:
return 0 # avoid exception caused by division by zero
pressure = 1048576.0 - adc_P
pressure = (pressure - (var2 / 4096.0)) * 6250.0 / var1
var1 = (self.dig_P9) * pressure * pressure / 2147483648.0
var2 = pressure * (self.dig_P8) / 32768.0
pressure = pressure + (var1 + var2 + (self.dig_P7)) / 16.0
return pressure
def get_temperature(self):
xlsb = self.read_byte(BMP280_TEMP_XLSB_REG)
lsb = self.read_byte(BMP280_TEMP_LSB_REG)
msb = self.read_byte(BMP280_TEMP_MSB_REG)
adc_T = (msb << 12) | (lsb << 4) | (xlsb >> 4)
temperature = self.compensate_temperature(adc_T)
return temperature # temperature in deg. C
def get_pressure(self):
xlsb = self.read_byte(BMP280_PRESS_XLSB_REG)
lsb = self.read_byte(BMP280_PRESS_LSB_REG)
msb = self.read_byte(BMP280_PRESS_MSB_REG)
adc_P = (msb << 12) | (lsb << 4) | (xlsb >> 4)
pressure = self.compensate_pressure(adc_P)
pressure = (pressure / 100.0)
pressure = (pressure + (ELEVATION / 9.2))
return pressure #pressure in mbar