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bme280.py
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bme280.py
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# Modified the following open source script to work with Raspberry Pi from the Control Everything Python Lib:
# Distributed with a free-will license.
# Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
# BME280
# This code is designed to work with the BME280_I2CS I2C Mini Module available from ControlEverything.com.
# https://www.controleverything.com/content/Humidity?sku=BME280_I2CS#tabs-0-product_tabset-2
import smbus
import time
from correct_temp import correct_temp
# Get I2C bus
bus = smbus.SMBus(1)
# I2C address of the device
BME280_DEFAULT_ADDRESS = 0x77
# BME280 Register Map
BME280_DIG_T1_LSB_REG = 0x88 # Calibration Data
BME280_DIG_T1_MSB_REG = 0x89 # Calibration Data
BME280_DIG_T2_LSB_REG = 0x8A # Calibration Data
BME280_DIG_T2_MSB_REG = 0x8B # Calibration Data
BME280_DIG_T3_LSB_REG = 0x8C # Calibration Data
BME280_DIG_T3_MSB_REG = 0x8D # Calibration Data
BME280_DIG_P1_LSB_REG = 0x8E # Calibration Data
BME280_DIG_P1_MSB_REG = 0x8F # Calibration Data
BME280_DIG_P2_LSB_REG = 0x90 # Calibration Data
BME280_DIG_P2_MSB_REG = 0x91 # Calibration Data
BME280_DIG_P3_LSB_REG = 0x92 # Calibration Data
BME280_DIG_P3_MSB_REG = 0x93 # Calibration Data
BME280_DIG_P4_LSB_REG = 0x94 # Calibration Data
BME280_DIG_P4_MSB_REG = 0x95 # Calibration Data
BME280_DIG_P5_LSB_REG = 0x96 # Calibration Data
BME280_DIG_P5_MSB_REG = 0x97 # Calibration Data
BME280_DIG_P6_LSB_REG = 0x98 # Calibration Data
BME280_DIG_P6_MSB_REG = 0x99 # Calibration Data
BME280_DIG_P7_LSB_REG = 0x9A # Calibration Data
BME280_DIG_P7_MSB_REG = 0x9B # Calibration Data
BME280_DIG_P8_LSB_REG = 0x9C # Calibration Data
BME280_DIG_P8_MSB_REG = 0x9D # Calibration Data
BME280_DIG_P9_LSB_REG = 0x9E # Calibration Data
BME280_DIG_P9_MSB_REG = 0x9F # Calibration Data
BME280_DIG_H1_REG = 0xA1 # Calibration Data
BME280_CHIP_ID_REG = 0xD0 # Chip ID
BME280_RST_REG = 0xE0 # Softreset Register
BME280_DIG_H2_LSB_REG = 0xE1 # Calibration Data
BME280_DIG_H2_MSB_REG = 0xE2 # Calibration Data
BME280_DIG_H3_REG = 0xE3 # Calibration Data
BME280_DIG_H4_MSB_REG = 0xE4 # Calibration Data
BME280_DIG_H4_LSB_REG = 0xE5 # Calibration Data
BME280_DIG_H5_MSB_REG = 0xE6 # Calibration Data
BME280_DIG_H6_REG = 0xE7 # Calibration Data
BME280_CTRL_HUMIDITY_REG = 0xF2 # Control Humidity Register
BME280_STAT_REG = 0xF3 # Status Register
BME280_CTRL_MEAS_REG = 0xF4 # Control Measure Register
BME280_CONFIG_REG = 0xF5 # Configuration Register
BME280_PRESSURE_MSB_REG = 0xF7 # Pressure MSB
BME280_PRESSURE_LSB_REG = 0xF8 # Pressure LSB
BME280_PRESSURE_XLSB_REG = 0xF9 # Pressure XLSB
BME280_TEMPERATURE_MSB_REG = 0xFA # Temperature MSB
BME280_TEMPERATURE_LSB_REG = 0xFB # Temperature LSB
BME280_TEMPERATURE_XLSB_REG = 0xFC # Temperature XLSB
BME280_HUMIDITY_MSB_REG = 0xFD # Humidity MSB
BME280_HUMIDITY_LSB_REG = 0xFE # Humidity LSB
# BME280 Control Humidity Register Configuration
BME280_H_OVERSAMPLE_NONE = 0x00 # Skipped
BME280_H_OVERSAMPLE_1 = 0x01 # Oversampling x 1
BME280_H_OVERSAMPLE_2 = 0x02 # Oversampling x 2
BME280_H_OVERSAMPLE_4 = 0x03 # Oversampling x 4
BME280_H_OVERSAMPLE_8 = 0x04 # Oversampling x 8
BME280_H_OVERSAMPLE_16 = 0x05 # Oversampling x 16
# BME280 Control Measure Register Configuration
BME280_P_OVERSAMPLE_NONE = 0x00 # Skipped
BME280_P_OVERSAMPLE_1 = 0x20 # Oversampling x 1
BME280_P_OVERSAMPLE_2 = 0x40 # Oversampling x 2
BME280_P_OVERSAMPLE_4 = 0x60 # Oversampling x 4
BME280_P_OVERSAMPLE_8 = 0x80 # Oversampling x 8
BME280_P_OVERSAMPLE_16 = 0xA0 # Oversampling x 16
BME280_T_OVERSAMPLE_NONE = 0x00 # Skipped
BME280_T_OVERSAMPLE_1 = 0x04 # Oversampling x 1
BME280_T_OVERSAMPLE_2 = 0x08 # Oversampling x 2
BME280_T_OVERSAMPLE_4 = 0x0C # Oversampling x 4
BME280_T_OVERSAMPLE_8 = 0x10 # Oversampling x 8
BME280_T_OVERSAMPLE_16 = 0x14 # Oversampling x 16
BME280_MODE_SLEEP = 0x00 # Sleep Mode
BME280_MODE_FORCED = 0x01 # Forced Mode
BME280_MODE_NORMAL = 0x03 # Normal Mode
# BME280 Configuration Register
BME280_STANDBY_MS_0_5 = 0x00 # Standby Time = 0.5ms
BME280_STANDBY_MS_10 = 0xC0 # Standby Time = 10ms
BME280_STANDBY_MS_20 = 0xD0 # Standby Time = 20ms
BME280_STANDBY_MS_62_5 = 0x20 # Standby Time = 62.5ms
BME280_STANDBY_MS_125 = 0x40 # Standby Time = 125ms
BME280_STANDBY_MS_250 = 0x60 # Standby Time = 250ms
BME280_STANDBY_MS_500 = 0x80 # Standby Time = 500ms
BME280_STANDBY_MS_1000 = 0xA0 # Standby Time = 1000ms
BME280_FILTER_OFF = 0x00 # Filter Off
BME280_FILTER_X2 = 0x04 # Filter Coefficient = 2
BME280_FILTER_X4 = 0x08 # Filter Coefficient = 4
BME280_FILTER_X8 = 0x0C # Filter Coefficient = 8
BME280_FILTER_X16 = 0x10 # Filter Coefficient = 16
BME280_SPI3_EN = 0x01 # Enables 3-wire SPI interface
class BME280():
def read_pres_temp_coeff(self):
"""Read data back from BME280_DIG_T1_LSB_REG(0x88), 24 bytes"""
b1 = bus.read_i2c_block_data(BME280_DEFAULT_ADDRESS, BME280_DIG_T1_LSB_REG, 24)
# Temp coefficients
self.dig_T1 = b1[1] * 256 + b1[0]
self.dig_T2 = b1[3] * 256 + b1[2]
if self.dig_T2 > 32767 :
self.dig_T2 -= 65536
self.dig_T3 = b1[5] * 256 + b1[4]
if self.dig_T3 > 32767 :
self.dig_T3 -= 65536
# Pressure coefficients
self.dig_P1 = b1[7] * 256 + b1[6]
self.dig_P2 = b1[9] * 256 + b1[8]
if self.dig_P2 > 32767 :
self.dig_P2 -= 65536
self.dig_P3 = b1[11] * 256 + b1[10]
if self.dig_P3 > 32767 :
self.dig_P3 -= 65536
self.dig_P4 = b1[13] * 256 + b1[12]
if self.dig_P4 > 32767 :
self.dig_P4 -= 65536
self.dig_P5 = b1[15] * 256 + b1[14]
if self.dig_P5 > 32767 :
self.dig_P5 -= 65536
self.dig_P6 = b1[17] * 256 + b1[16]
if self.dig_P6 > 32767 :
self.dig_P6 -= 65536
self.dig_P7 = b1[19] * 256 + b1[18]
if self.dig_P7 > 32767 :
self.dig_P7 -= 65536
self.dig_P8 = b1[21] * 256 + b1[20]
if self.dig_P8 > 32767 :
self.dig_P8 -= 65536
self.dig_P9 = b1[23] * 256 + b1[22]
if self.dig_P9 > 32767 :
self.dig_P9 -= 65536
def read_hum_coeff(self):
"""Read data back from BME280_DIG_H1_REG(0xA1), 1 byte"""
self.dig_H1 = bus.read_byte_data(BME280_DEFAULT_ADDRESS, BME280_DIG_H1_REG)
"""Read data back from BME280_DIG_H2_LSB_REG(0xE1), 7 bytes"""
b1 = bus.read_i2c_block_data(BME280_DEFAULT_ADDRESS, BME280_DIG_H2_LSB_REG, 7)
# Humidity coefficients
self.dig_H2 = b1[1] * 256 + b1[0]
if self.dig_H2 > 32767 :
self.dig_H2 -= 65536
self.dig_H3 = (b1[2] & 0xFF)
self.dig_H4 = (b1[3] * 16) + (b1[4] & 0xF)
if self.dig_H4 > 32767 :
self.dig_H4 -= 65536
self.dig_H5 = (b1[4] / 16) + (b1[5] * 16)
if self.dig_H5 > 32767 :
self.dig_H5 -= 65536
self.dig_H6 = b1[6]
if self.dig_H6 > 127 :
self.dig_H6 -= 256
def write_configuration(self):
"""Select the Control Humidity Register Configuration from the given provided value"""
HUMIDITY_SAMPLE = (BME280_H_OVERSAMPLE_1)
bus.write_byte_data(BME280_DEFAULT_ADDRESS, BME280_CTRL_HUMIDITY_REG, HUMIDITY_SAMPLE)
"""Select the Control Measure Register Configuration from the given provided value"""
PRES_TEMP_SAMPLE = (BME280_P_OVERSAMPLE_1 | BME280_T_OVERSAMPLE_1 | BME280_MODE_NORMAL)
bus.write_byte_data(BME280_DEFAULT_ADDRESS, BME280_CTRL_MEAS_REG, PRES_TEMP_SAMPLE)
"""Select the Configuration Register data from the given provided value"""
TIME_CONFIG = (BME280_STANDBY_MS_1000 | BME280_FILTER_OFF)
bus.write_byte_data(BME280_DEFAULT_ADDRESS, BME280_CONFIG_REG, TIME_CONFIG)
def read_data(self):
"""Read data back from BME280_PRESSURE_MSB_REG(0xF7), 8 bytes
Pressure MSB, Pressure LSB, Pressure xLSB, Temperature MSB, Temperature LSB
Temperature xLSB, Humidity MSB, Humidity LSB"""
data = bus.read_i2c_block_data(BME280_DEFAULT_ADDRESS, BME280_PRESSURE_MSB_REG, 8)
# Convert pressure and temperature data to 19-bits
self.adc_p = ((data[0] * 65536) + (data[1] * 256) + (data[2] & 0xF0)) / 16
self.adc_t = ((data[3] * 65536) + (data[4] * 256) + (data[5] & 0xF0)) / 16
# Convert the humidity data
self.adc_h = data[6] * 256 + data[7]
def result_calculation(self):
"""Offset calculations for the final pressure, humidity and temperature"""
# Temperature offset calculations
var1 = ((self.adc_t) / 16384.0 - (self.dig_T1) / 1024.0) * (self.dig_T2)
var2 = (((self.adc_t) / 131072.0 - (self.dig_T1) / 8192.0) * ((self.adc_t)/131072.0 - (self.dig_T1)/8192.0)) * (self.dig_T3)
t_fine = (var1 + var2)
cTemp = (var1 + var2) / 5120.0
fTemp = cTemp * 1.8 + 32
# Pressure offset calculations
var1 = (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)
p = 1048576.0 - self.adc_p
p = (p - (var2 / 4096.0)) * 6250.0 / var1
var1 = (self.dig_P9) * p * p / 2147483648.0
var2 = p * (self.dig_P8) / 32768.0
pressure = (p + (var1 + var2 + (self.dig_P7)) / 16.0) / 100
# Humidity offset calculations
var_H = ((t_fine) - 76800.0)
var_H = (self.adc_h - (self.dig_H4 * 64.0 + self.dig_H5 / 16384.0 * var_H)) * (self.dig_H2 / 65536.0 * (1.0 + self.dig_H6 / 67108864.0 * var_H * (1.0 + self.dig_H3 / 67108864.0 * var_H)))
humidity = var_H * (1.0 - self.dig_H1 * var_H / 524288.0)
if humidity > 100.0 :
humidity = 100.0
elif humidity < 0.0 :
humidity = 0.0
return {'h' : humidity, 'p' : pressure, 'c' : cTemp, 'f' : fTemp}
bme280 = BME280()
def get_bme280_data():
bme280.read_pres_temp_coeff()
bme280.read_hum_coeff()
bme280.write_configuration()
bme280.read_data()
data = bme280.result_calculation()
air_temp, air_pressure, humidity = round(data['c'], 2), round(data['p'], 2), round(data['h'], 2)
# correct temp accounting for heat from Pi CPU
air_temp = correct_temp(air_temp)
return air_temp, air_pressure, humidity
if __name__ == "__main__":
while True :
bme280.read_pres_temp_coeff()
bme280.read_hum_coeff()
bme280.write_configuration()
bme280.read_data()
data = bme280.result_calculation()
print("Pressure : %.2f hPa"%(data['p']))
print("Relative Humidity : %.2f %%"%(data['h']))
print("Temperature in Celsius : %.2f C"%(data['c']))
print("Temperature in Fahrenheit : %.2f F"%(data['f']))
print(" ***************************************** ")
time.sleep(0.7)