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BME280.py
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BME280.py
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
import smbus
import time
# BME280 default address.
BME280_I2CADDR = 0x76
# BME280 Registers
BME280_CONTROL_MEAS = 0xF4
BME280_CONTROL_HUM = 0xF2
BME280_CONFIG = 0xF5
BME280_PRESSURE = 0xF7
BME280_TEMP = 0xFA
BME280_HUMIDITY = 0xFD
BME280_DIG_T1 = 0x88
BME280_DIG_T2 = 0x8A
BME280_DIG_T3 = 0x8C
BME280_DIG_P1 = 0x8E
BME280_DIG_P2 = 0x90
BME280_DIG_P3 = 0x92
BME280_DIG_P4 = 0x94
BME280_DIG_P5 = 0x96
BME280_DIG_P6 = 0x98
BME280_DIG_P7 = 0x9A
BME280_DIG_P8 = 0x9C
BME280_DIG_P9 = 0x9E
BME280_DIG_H1 = 0xA1
BME280_DIG_H2 = 0xE1
BME280_DIG_H3 = 0xE3
BME280_DIG_H4 = 0xE4
BME280_DIG_H5 = 0xE5
BME280_DIG_H6 = 0xE7
# Oversampling Setting
BME280_OVERS_T1 = 0x20
BME280_OVERS_T2 = 0x40
BME280_OVERS_T4 = 0x60
BME280_OVERS_T8 = 0x80
BME280_OVERS_T16 = 0xA0
BME280_OVERS_P1 = 0x04
BME280_OVERS_P2 = 0x08
BME280_OVERS_P4 = 0x0C
BME280_OVERS_P8 = 0x10
BME280_OVERS_P16 = 0x14
BME280_OVERS_H1 = 0x01
BME280_OVERS_H2 = 0x02
BME280_OVERS_H4 = 0x03
BME280_OVERS_H8 = 0x04
BME280_OVERS_H16 = 0x05
# Power Modes.
# This lib uses NORMAL mode only!
#BME280_SLEEP_MODE = 0x00
#BME280_FORCED_MODE = 0x01
BME280_NORMAL_MODE = 0x03
BME280_TSB_0_5 = 0x00
BME280_TSB_62_5 = 0x20
BME280_TSB_125 = 0x40
BME280_TSB_250 = 0x60
BME280_TSB_500 = 0x80
BME280_TSB_1000 = 0xA0
BME280_TSB_2000 = 0xC0
BME280_TSB_4000 = 0xE0
BME280_FILTER_OFF = 0x00
BME280_FILTER_COEFFICIENT2 = 0x04
BME280_FILTER_COEFFICIENT4 = 0x08
BME280_FILTER_COEFFICIENT8 = 0x0C
BME280_FILTER_COEFFICIENT16 = 0x10
BME280_SPI_OFF = 0x00
BME280_SPI_ON = 0x01
BME280_CONTROL_MEAS_SET = (BME280_OVERS_T16 | BME280_OVERS_P16 | BME280_NORMAL_MODE)
BME280_CONTROL_HUM_SET = BME280_OVERS_H2
BME280_CONFIG_SET = (BME280_TSB_0_5 | BME280_FILTER_COEFFICIENT16 | BME280_SPI_OFF)
class BME280(object):
def __init__(self, port=1, address=BME280_I2CADDR):
self.bus = smbus.SMBus(port)
self.address = address
# Read calibration values
self.dig_t1 = self.read_word(BME280_DIG_T1) # Unsigned
self.dig_t2 = self.read_word_sign(BME280_DIG_T2)
self.dig_t3 = self.read_word_sign(BME280_DIG_T3)
self.dig_p1 = self.read_word(BME280_DIG_P1) # Unsigned
self.dig_p2 = self.read_word_sign(BME280_DIG_P2)
self.dig_p3 = self.read_word_sign(BME280_DIG_P3)
self.dig_p4 = self.read_word_sign(BME280_DIG_P4)
self.dig_p5 = self.read_word_sign(BME280_DIG_P5)
self.dig_p6 = self.read_word_sign(BME280_DIG_P6)
self.dig_p7 = self.read_word_sign(BME280_DIG_P7)
self.dig_p8 = self.read_word_sign(BME280_DIG_P8)
self.dig_p9 = self.read_word_sign(BME280_DIG_P9)
self.dig_h1 = self.read_byte(BME280_DIG_H1) # unsigned char
self.dig_h2 = self.read_word_sign(BME280_DIG_H2)
self.dig_h3 = self.read_byte(BME280_DIG_H3) # unsigned char
self.dig_h4 = (self.read_byte(BME280_DIG_H4) << 24) >> 20
self.dig_h4 = self.dig_h4 | self.read_byte(BME280_DIG_H4+1) & 0x0F
self.dig_h5 = (self.read_byte(BME280_DIG_H5+1) << 24) >> 20
self.dig_h5 = self.dig_h5 | (self.read_byte(BME280_DIG_H5) >> 4) & 0x0F
self.dig_h6 = self.read_byte(BME280_DIG_H6) # signed char
if self.dig_h6 > 127:
self.dig_h6 = 127-self.dig_h6
# Set Configuration
self.write_byte(BME280_CONFIG, BME280_CONFIG_SET)
self.write_byte(BME280_CONTROL_HUM, BME280_CONTROL_HUM_SET)
self.write_byte(BME280_CONTROL_MEAS, BME280_CONTROL_MEAS_SET)
def get_data(self):
adc_t = self.read_adc_long(BME280_TEMP)
adc_p = self.read_adc_long(BME280_PRESSURE)
adc_h = self.read_adc_word(BME280_HUMIDITY)
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;
t_fine = (var1 + var2);
temperature = round((t_fine / 5120.0), 2);
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;
# Avoid exception caused by division by zero
if (var1 == 0.0):
return -1
p = 1048576.0 - 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 = round((p + (var1 + var2 + self.dig_p7) / 16.0), 2);
var_H = t_fine - 76800.0
var_H = (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 = round(var_H * (1.0 - self.dig_h1*var_H/524288.0), 2)
if (humidity > 100.0):
humidity = 100.0
else:
if(humidity < 0.0):
humidity = 0.0
return {'t':temperature, 'p':pressure, 'h':humidity}
def get_altitude(self, pressure):
temp = pressure/101325;
temp = 1-pow(temp, 0.19029);
altitude = round(44330*temp, 3);
return altitude;
def read_byte(self, adr):
return self.bus.read_byte_data(self.address, adr)
def read_word(self, adr):
# ATANTION! Joke from Bosch! LBS before HBS. For calibration registers only!
lbs = self.bus.read_byte_data(self.address, adr)
hbs = self.bus.read_byte_data(self.address, adr+1)
return (hbs << 8) + lbs
def read_word_sign(self, adr):
val = self.read_word(adr)
if (val >= 0x8000):
return -((65535 - val) + 1)
else:
return val
def read_adc_long(self, adr):
mbs = self.bus.read_byte_data(self.address, adr)
lbs = self.bus.read_byte_data(self.address, adr+1)
xbs = self.bus.read_byte_data(self.address, adr+2)
val = (mbs << 16) + (lbs << 8) + xbs
val = (val >> 4)
return val
def read_adc_word(self, adr):
mbs = self.bus.read_byte_data(self.address, adr)
lbs = self.bus.read_byte_data(self.address, adr+1)
val = (mbs << 8) + lbs
return val
def write_byte(self, adr, byte):
self.bus.write_byte_data(self.address, adr, byte)