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import time
import smbus
to_s16 = lambda x: (x + 2**15) % 2**16 - 2**15
to_s8 = lambda x: (x + 2**7) % 2**8 - 2**7
to_u16 = lambda x: x % 2**16
BME280_I2C_ADDR = 0x76
BME280_CHIP_ID = 0x60
power_mode = {
"BME280_SLEEP_MODE" : 0x00,
"BME280_FORCED_MODE" : 0x01,
"BME280_NORMAL_MODE" : 0x03,
"BME280_SOFT_RESET_CODE" : 0xB6,
}
regs = {
"BME280_CHIP_ID_REG" : 0xD0,
"BME280_RST_REG" : 0xE0,
"BME280_STAT_REG" : 0xF3,
"BME280_CTRL_MEAS_REG" : 0xF4,
"BME280_CTRL_HUMIDITY_REG" : 0xF2,
"BME280_CONFIG_REG" : 0xF5,
"BME280_PRESSURE_MSB_REG" : 0xF7,
"BME280_PRESSURE_LSB_REG" : 0xF8,
"BME280_PRESSURE_XLSB_REG" : 0xF9,
"BME280_TEMPERATURE_MSB_REG" : 0xFA,
"BME280_TEMPERATURE_LSB_REG" : 0xFB,
"BME280_TEMPERATURE_XLSB_REG" : 0xFC,
"BME280_HUMIDITY_MSB_REG" : 0xFD,
"BME280_HUMIDITY_LSB_REG" : 0xFE,
}
cali_regs = {
"BME280_TEMPERATURE_CALIB_DIG_T1_LSB_REG" : 0x88,
"BME280_TEMPERATURE_CALIB_DIG_T1_MSB_REG" : 0x89,
"BME280_TEMPERATURE_CALIB_DIG_T2_LSB_REG" : 0x8A,
"BME280_TEMPERATURE_CALIB_DIG_T2_MSB_REG" : 0x8B,
"BME280_TEMPERATURE_CALIB_DIG_T3_LSB_REG" : 0x8C,
"BME280_TEMPERATURE_CALIB_DIG_T3_MSB_REG" : 0x8D,
"BME280_PRESSURE_CALIB_DIG_P1_LSB_REG" : 0x8E,
"BME280_PRESSURE_CALIB_DIG_P1_MSB_REG" : 0x8F,
"BME280_PRESSURE_CALIB_DIG_P2_LSB_REG" : 0x90,
"BME280_PRESSURE_CALIB_DIG_P2_MSB_REG" : 0x91,
"BME280_PRESSURE_CALIB_DIG_P3_LSB_REG" : 0x92,
"BME280_PRESSURE_CALIB_DIG_P3_MSB_REG" : 0x93,
"BME280_PRESSURE_CALIB_DIG_P4_LSB_REG" : 0x94,
"BME280_PRESSURE_CALIB_DIG_P4_MSB_REG" : 0x95,
"BME280_PRESSURE_CALIB_DIG_P5_LSB_REG" : 0x96,
"BME280_PRESSURE_CALIB_DIG_P5_MSB_REG" : 0x97,
"BME280_PRESSURE_CALIB_DIG_P6_LSB_REG" : 0x98,
"BME280_PRESSURE_CALIB_DIG_P6_MSB_REG" : 0x99,
"BME280_PRESSURE_CALIB_DIG_P7_LSB_REG" : 0x9A,
"BME280_PRESSURE_CALIB_DIG_P7_MSB_REG" : 0x9B,
"BME280_PRESSURE_CALIB_DIG_P8_LSB_REG" : 0x9C,
"BME280_PRESSURE_CALIB_DIG_P8_MSB_REG" : 0x9D,
"BME280_PRESSURE_CALIB_DIG_P9_LSB_REG" : 0x9E,
"BME280_PRESSURE_CALIB_DIG_P9_MSB_REG" : 0x9F,
"BME280_HUMIDITY_CALIB_DIG_H1_REG" : 0xA1,
"BME280_HUMIDITY_CALIB_DIG_H2_LSB_REG" : 0xE1,
"BME280_HUMIDITY_CALIB_DIG_H2_MSB_REG" : 0xE2,
"BME280_HUMIDITY_CALIB_DIG_H3_REG" : 0xE3,
"BME280_HUMIDITY_CALIB_DIG_H4_MSB_REG" : 0xE4,
"BME280_HUMIDITY_CALIB_DIG_H4_LSB_REG" : 0xE5,
"BME280_HUMIDITY_CALIB_DIG_H5_MSB_REG" : 0xE6,
"BME280_HUMIDITY_CALIB_DIG_H6_REG" : 0xE7,
}
class BME280:
param = {}
def __init__(self, i2c_dev, p_mode, h_samp, p_samp, t_samp):
self.bus = smbus.SMBus(int(i2c_dev.split('-')[-1]))
self.chip_id = self.read(regs['BME280_CHIP_ID_REG'], 1)[0]
if self.chip_id != BME280_CHIP_ID:
print("Wrong Device ID [", hex(self.chip_id), "]")
exit()
self.config_reg = 0
self.ctrl_meas_reg = 0
self.ctrl_hum_reg = 0
self.oversamp_humidity = 0
self.oversamp_pressure = 0
self.get_cal_param()
self.set_power_mode(p_mode)
self.set_oversamp_humidity(h_samp)
self.set_oversamp_pressure(p_samp)
self.set_oversamp_temperature(t_samp)
time.sleep(0.01)
self.t_fine = 0.0
def read(self, reg, cnt):
val = [0 for x in range(cnt)]
for i in range(cnt):
val[i] = self.bus.read_byte_data(BME280_I2C_ADDR, reg + i)
return val
def write(self, reg, val):
for i in range(len(val)):
self.bus.write_byte_data(BME280_I2C_ADDR, reg + i, val[i])
def get_cal_param(self):
params = self.read(cali_regs['BME280_TEMPERATURE_CALIB_DIG_T1_LSB_REG'], 26)
self.param['dig_T1'] = to_u16((params[1] << 8) | params[0])
self.param['dig_T2'] = to_s16((params[3] << 8) | params[2])
self.param['dig_T3'] = to_s16((params[5] << 8) | params[4])
self.param['dig_P1'] = to_u16((params[7] << 8) | params[6])
self.param['dig_P2'] = to_s16((params[9] << 8) | params[8])
self.param['dig_P3'] = to_s16((params[11] << 8) | params[10])
self.param['dig_P4'] = to_s16((params[13] << 8) | params[12])
self.param['dig_P5'] = to_s16((params[15] << 8) | params[14])
self.param['dig_P6'] = to_s16((params[17] << 8) | params[16])
self.param['dig_P7'] = to_s16((params[19] << 8) | params[18])
self.param['dig_P8'] = to_s16((params[21] << 8) | params[20])
self.param['dig_P9'] = to_s16((params[23] << 8) | params[22])
self.param['dig_H1'] = params[25]
params = self.read(cali_regs['BME280_HUMIDITY_CALIB_DIG_H2_LSB_REG'], 7)
self.param['dig_H2'] = to_s16((params[1] << 8) | params[0])
self.param['dig_H3'] = params[2]
# FIX: dig_H4/H5 are 12-bit signed values. Must sign-extend from the
# MSB byte first, then combine with the LSB nibble — matching the Bosch
# BME280_SensorAPI parse_humidity_calib_data() which does:
# dig_h4_msb = (int16_t)(int8_t)reg_data[3] * 16;
# dig_h4 = dig_h4_msb | (reg_data[4] & 0x0F);
# The old code used to_s16() which only sign-extends at the 16-bit
# boundary, giving wrong results when the 12-bit value is negative.
self.param['dig_H4'] = (to_s8(params[3]) << 4) | (params[4] & 0x0f)
self.param['dig_H5'] = (to_s8(params[5]) << 4) | (params[4] >> 4)
# FIX: dig_H6 is int8_t per Bosch API (bme280_defs.h) and Adafruit.
# Was stored unsigned, which gives wrong humidity for sensors where
# this calibration coefficient is negative.
self.param['dig_H6'] = to_s8(params[6])
def get_power_mode(self):
return self.read(regs['BME280_CTRL_MEAS_REG'], 1)[0] & 0x03
def set_power_mode(self, p_mode):
if p_mode <= power_mode['BME280_NORMAL_MODE']:
v_mode = (self.ctrl_meas_reg & ~0x03) | (p_mode & 0x03)
if self.get_power_mode() != power_mode['BME280_SLEEP_MODE']:
self.soft_rst()
time.sleep(0.003)
self.write(regs['BME280_CONFIG_REG'], [self.config_reg])
self.write(regs['BME280_CTRL_HUMIDITY_REG'], [self.ctrl_hum_reg])
self.write(regs['BME280_CTRL_MEAS_REG'], [v_mode])
else:
self.write(regs['BME280_CTRL_MEAS_REG'], [v_mode])
self.ctrl_meas_reg = self.read(regs['BME280_CTRL_MEAS_REG'], 1)[0]
self.ctrl_hum_reg = self.read(regs['BME280_CTRL_HUMIDITY_REG'], 1)[0]
self.config_reg = self.read(regs['BME280_CONFIG_REG'], 1)[0]
else:
print("Wrong Power Mode [", hex(p_mode), "]")
exit()
def soft_rst(self):
self.write(regs['BME280_RST_REG'], [power_mode['BME280_SOFT_RESET_CODE']])
def set_oversamp_humidity(self, sampling):
v_data = (self.ctrl_hum_reg & ~0x07) | (sampling & 0x07)
if self.get_power_mode() != power_mode['BME280_SLEEP_MODE']:
self.soft_rst()
time.sleep(0.003)
self.write(regs['BME280_CONFIG_REG'], [self.config_reg])
self.write(regs['BME280_CTRL_HUMIDITY_REG'], [v_data])
self.write(regs['BME280_CTRL_MEAS_REG'], [self.ctrl_meas_reg])
else:
self.write(regs['BME280_CTRL_HUMIDITY_REG'], [v_data])
# FIX: Was writing ctrl_hum_reg into CTRL_MEAS register (wrong
# value in wrong register). Per datasheet section 5.4.3, humidity
# settings only take effect after a write to ctrl_meas — but we
# must write the actual ctrl_meas value, not the humidity one.
# Matches Adafruit setSampling() and Bosch set_osr_humidity_settings().
self.write(regs['BME280_CTRL_MEAS_REG'], [self.ctrl_meas_reg])
self.oversamp_humidity = sampling
self.ctrl_meas_reg = self.read(regs['BME280_CTRL_MEAS_REG'], 1)[0]
self.ctrl_hum_reg = self.read(regs['BME280_CTRL_HUMIDITY_REG'], 1)[0]
self.config_reg = self.read(regs['BME280_CONFIG_REG'], 1)[0]
def set_oversamp_pressure(self, sampling):
v_data = (self.ctrl_meas_reg & ~0x1c) | ((sampling << 2) & 0x1c)
# FIX: Was missing () on get_power_mode — compared the method object
# (always truthy) to an int, so the sleep-mode check never worked.
# Matches set_power_mode() and set_oversamp_humidity() which both
# correctly call self.get_power_mode().
if self.get_power_mode() != power_mode['BME280_SLEEP_MODE']:
self.soft_rst()
time.sleep(0.003)
self.write(regs['BME280_CONFIG_REG'], [self.config_reg])
self.write(regs['BME280_CTRL_HUMIDITY_REG'], [self.ctrl_hum_reg])
self.write(regs['BME280_CTRL_MEAS_REG'], [v_data])
else:
self.write(regs['BME280_CTRL_MEAS_REG'], [v_data])
self.oversamp_pressure = sampling
self.ctrl_meas_reg = self.read(regs['BME280_CTRL_MEAS_REG'], 1)[0]
self.ctrl_hum_reg = self.read(regs['BME280_CTRL_HUMIDITY_REG'], 1)[0]
self.config_reg = self.read(regs['BME280_CONFIG_REG'], 1)[0]
def set_oversamp_temperature(self, sampling):
v_data = (self.ctrl_meas_reg & ~0xe0) | ((sampling << 5) & 0xe0)
# FIX: Same missing () bug as set_oversamp_pressure — see above.
if self.get_power_mode() != power_mode['BME280_SLEEP_MODE']:
self.soft_rst()
time.sleep(0.003)
self.write(regs['BME280_CONFIG_REG'], [self.config_reg])
self.write(regs['BME280_CTRL_HUMIDITY_REG'], [self.ctrl_hum_reg])
self.write(regs['BME280_CTRL_MEAS_REG'], [v_data])
else:
self.write(regs['BME280_CTRL_MEAS_REG'], [v_data])
self.oversamp_temperature = sampling
self.ctrl_meas_reg = self.read(regs['BME280_CTRL_MEAS_REG'], 1)[0]
self.ctrl_hum_reg = self.read(regs['BME280_CTRL_HUMIDITY_REG'], 1)[0]
self.config_reg = self.read(regs['BME280_CONFIG_REG'], 1)[0]
def read_humidity(self):
vals = self.read(regs['BME280_PRESSURE_MSB_REG'], 8)
raw_val = float((vals[6] << 8) | vals[7])
"""
x1 = self.t_fine - 76800
x1 = ((((raw_val << 14) - (self.param['dig_H4'] << 20) - (self.param['dig_H5'] * x1)) + 16384) >> 15) * \
(((((((x1 * self.param['dig_H6']) >> 10) * (((x1 * self.param['dig_H3']) >> 11) + 32768)) >> 10) + 2097152) * \
self.param['dig_H2'] + 8192) >> 14)
x1 = x1 - (((((x1 >> 15) ** 2) >> 7) * self.param['dig_H1']) >> 4)
if x1 < 0:
x1 = 0
if x1 > 419430400:
x1 = 419430400
return (x1 >> 12) / 1024.0
"""
# FIX: Humidity compensation rewritten to match Bosch BME280_SensorAPI
# compensate_humidity() (BME280_DOUBLE_ENABLE path in bme280.c).
# The old code was missing the var5 multiplication factor, producing
# incorrect humidity. The formula below uses the same variable names
# as the Bosch reference for easy cross-referencing.
var1 = float(self.t_fine) - 76800.0
var2 = float(self.param['dig_H4']) * 64.0 + (float(self.param['dig_H5']) / 16384.0) * var1
var3 = raw_val - var2
var4 = float(self.param['dig_H2']) / 65536.0
var5 = 1.0 + (float(self.param['dig_H3']) / 67108864.0) * var1
var6 = 1.0 + (float(self.param['dig_H6']) / 67108864.0) * var1 * var5
var6 = var3 * var4 * (var5 * var6)
h = var6 * (1.0 - float(self.param['dig_H1']) * var6 / 524288.0)
if h > 100:
h = 100
elif h < 0:
h = 0
return h
def read_pressure(self):
vals = self.read(regs['BME280_PRESSURE_MSB_REG'], 8)
raw_val = float((vals[0] << 12) | (vals[1] << 4) | (vals[2] >> 4))
"""
x1 = (self.t_fine >> 1) - 64000
x2 = (((x1 >> 2) ** 2) >> 11) * self.param['dig_P6']
x2 = x2 + ((x1 * self.param['dig_P5']) << 1)
x2 = (x2 >> 2) + (self.param['dig_P4'] << 16)
x1 = ((self.param['dig_P3'] * (((x1 >> 2) ** 2) >> 13)) >> 3 + \
((self.param['dig_P2'] * x1) >> 1)) >> 18
x1 = ((32768 + x1) * self.param['dig_P1']) >> 15
p = ((1048576 - raw_val) - (x2 >> 12)) * 3125
if x1 == 0:
return 0
if p < 0x80000000:
p = (p << 1) / x1
else:
p = (p / x1) * 2
x1 = (self.param['dig_P9'] * (((p >> 3) ** 2) >> 13)) >> 12
x2 = ((p >> 2) * self.param['dig_P8']) >> 13
p = p + ((x1 + x2 + self.param['dig_P7']) >> 4)
return p / 100.0
"""
var1 = float(self.t_fine) / 2.0 - 64000.0
var2 = var1 * var1 * float(self.param['dig_P6']) / 32768.0
var2 = var2 + var1 * float(self.param['dig_P5']) * 2.0
var2 = var2 / 4.0 + float(self.param['dig_P4']) * 65536.0
var1 = (
float(self.param['dig_P3']) * var1 * var1 / 524288.0 + float(self.param['dig_P2']) * var1) / 524288.0
var1 = (1.0 + var1 / 32768.0) * float(self.param['dig_P1'])
if var1 == 0:
return 0
p = 1048576.0 - raw_val
p = ((p - var2 / 4096.0) * 6250.0) / var1
var1 = float(self.param['dig_P9']) * p * p / 2147483648.0
var2 = p * float(self.param['dig_P8']) / 32768.0
p = p + (var1 + var2 + float(self.param['dig_P7'])) / 16.0
return p
def read_temperature(self):
vals = self.read(regs['BME280_PRESSURE_MSB_REG'], 8)
raw_val = float((vals[3] << 12) | (vals[4] << 4) | (vals[5] >> 4))
"""
x1 = (((raw_val >> 3) - (self.param['dig_T1'] << 1)) * self.param['dig_T2']) >> 11
x2 = (((((raw_val >> 4) - self.param['dig_T1']) * ((raw_val >> 4) - self.param['dig_T1'])) >> 12) * self.param['dig_T3']) >> 14
self.t_fine = x1 + x2
temp = (self.t_fine * 5 + 128) >> 8
return temp / 100.0
"""
var1 = (raw_val / 16384.0 - float(self.param['dig_T1']) / 1024.0) * float(self.param['dig_T2'])
var2 = ((raw_val / 131072.0 - float(self.param['dig_T1']) / 8192.0) * (
raw_val / 131072.0 - float(self.param['dig_T1']) / 8192.0)) * float(self.param['dig_T3'])
self.t_fine = int(var1 + var2)
temp = (var1 + var2) / 5120.0
return temp
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