BME280/Python/BME280.py at master · ControlEverythingCommunity/BME280 · GitHub

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# 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

importsmbus
importtime

# Get I2C bus
bus=smbus.SMBus(1)

# BME280 address, 0x76(118)
# Read data back from 0x88(136), 24 bytes
b1=bus.read_i2c_block_data(0x76, 0x88, 24)

# Convert the data
# Temp coefficients
dig_T1=b1[1] *256+b1[0]
dig_T2=b1[3] *256+b1[2]
ifdig_T2>32767 :
dig_T2-=65536
dig_T3=b1[5] *256+b1[4]
ifdig_T3>32767 :
dig_T3-=65536

# Pressure coefficients
dig_P1=b1[7] *256+b1[6]
dig_P2=b1[9] *256+b1[8]
ifdig_P2>32767 :
dig_P2-=65536
dig_P3=b1[11] *256+b1[10]
ifdig_P3>32767 :
dig_P3-=65536
dig_P4=b1[13] *256+b1[12]
ifdig_P4>32767 :
dig_P4-=65536
dig_P5=b1[15] *256+b1[14]
ifdig_P5>32767 :
dig_P5-=65536
dig_P6=b1[17] *256+b1[16]
ifdig_P6>32767 :
dig_P6-=65536
dig_P7=b1[19] *256+b1[18]
ifdig_P7>32767 :
dig_P7-=65536
dig_P8=b1[21] *256+b1[20]
ifdig_P8>32767 :
dig_P8-=65536
dig_P9=b1[23] *256+b1[22]
ifdig_P9>32767 :
dig_P9-=65536

# BME280 address, 0x76(118)
# Read data back from 0xA1(161), 1 byte
dig_H1=bus.read_byte_data(0x76, 0xA1)

# BME280 address, 0x76(118)
# Read data back from 0xE1(225), 7 bytes
b1=bus.read_i2c_block_data(0x76, 0xE1, 7)

# Convert the data
# Humidity coefficients
dig_H2=b1[1] *256+b1[0]
ifdig_H2>32767 :
dig_H2-=65536
dig_H3= (b1[2] &0xFF)
dig_H4= (b1[3] *16) + (b1[4] &0xF)
ifdig_H4>32767 :
dig_H4-=65536
dig_H5= (b1[4] /16) + (b1[5] *16)
ifdig_H5>32767 :
dig_H5-=65536
dig_H6=b1[6]
ifdig_H6>127 :
dig_H6-=256

# BME280 address, 0x76(118)
# Select control humidity register, 0xF2(242)
# 0x01(01)	Humidity Oversampling = 1
bus.write_byte_data(0x76, 0xF2, 0x01)
# BME280 address, 0x76(118)
# Select Control measurement register, 0xF4(244)
# 0x27(39)	Pressure and Temperature Oversampling rate = 1
# Normal mode
bus.write_byte_data(0x76, 0xF4, 0x27)
# BME280 address, 0x76(118)
# Select Configuration register, 0xF5(245)
# 0xA0(00)	Stand_by time = 1000 ms
bus.write_byte_data(0x76, 0xF5, 0xA0)

time.sleep(0.5)

# BME280 address, 0x76(118)
# Read data back from 0xF7(247), 8 bytes
# Pressure MSB, Pressure LSB, Pressure xLSB, Temperature MSB, Temperature LSB
# Temperature xLSB, Humidity MSB, Humidity LSB
data=bus.read_i2c_block_data(0x76, 0xF7, 8)

# Convert pressure and temperature data to 19-bits
adc_p= ((data[0] *65536) + (data[1] *256) + (data[2] &0xF0)) /16
adc_t= ((data[3] *65536) + (data[4] *256) + (data[5] &0xF0)) /16

# Convert the humidity data
adc_h=data[6] *256+data[7]

# Temperature offset calculations
var1= ((adc_t) /16384.0- (dig_T1) /1024.0) * (dig_T2)
var2= (((adc_t) /131072.0- (dig_T1) /8192.0) * ((adc_t)/131072.0- (dig_T1)/8192.0)) * (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* (dig_P6) /32768.0
var2=var2+var1* (dig_P5) *2.0
var2= (var2/4.0) + ((dig_P4) *65536.0)
var1= ((dig_P3) *var1*var1/524288.0+ ( dig_P2) *var1) /524288.0
var1= (1.0+var1/32768.0) * (dig_P1)
p=1048576.0-adc_p
p= (p- (var2/4096.0)) *6250.0/var1
var1= (dig_P9) *p*p/2147483648.0
var2=p* (dig_P8) /32768.0
pressure= (p+ (var1+var2+ (dig_P7)) /16.0) /100

# Humidity offset calculations
var_H= ((t_fine) -76800.0)
var_H= (adc_h- (dig_H4*64.0+dig_H5/16384.0*var_H)) * (dig_H2/65536.0* (1.0+dig_H6/67108864.0*var_H* (1.0+dig_H3/67108864.0*var_H)))
humidity=var_H* (1.0-dig_H1*var_H/524288.0)
ifhumidity>100.0 :
humidity=100.0
elifhumidity<0.0 :
humidity=0.0

# Output data to screen
print"Temperature in Celsius : %.2f C"%cTemp
print"Temperature in Fahrenheit : %.2f F"%fTemp
print"Pressure : %.2f hPa "%pressure
print"Relative Humidity : %.2f %%"%humidity