import time import smbus # pylint: disable=import-error ADDR = 0x76 # 7bit address of the BME280 for SDO=0, else 0x77 REGISTER_ID = 0xD0 REGISTER_RESET = 0xE0 REGISTER_CTRL_HUM = 0xF2 REGISTER_STATUS = 0xF3 REGISTER_CTRL_MEAS = 0xF4 REGISTER_CONFIG = 0xF5 HO_SKIPPED = 0x00 HO_1 = 0x01 HO_2 = 0x02 HO_4 = 0x03 HO_8 = 0x04 HO_16 = 0x05 # and all higher PO_SKIPPED = 0x00 PO_1 = 0x01 PO_2 = 0x02 PO_4 = 0x03 PO_8 = 0x04 PO_16 = 0x05 # and all higher TO_SKIPPED = 0x00 TO_1 = 0x01 TO_2 = 0x02 TO_4 = 0x03 TO_8 = 0x04 TO_16 = 0x05 # and all higher MODE_SLEEP = 0x00 MODE_FORCED = 0x01 # and 0x02 MODE_NORMAL = 0x03 TSTANDBY_0_5 = 0x00 TSTANDBY_62_5 = 0x01 TSTANDBY_125 = 0x02 TSTANDBY_250 = 0x03 TSTANDBY_500 = 0x04 TSTANDBY_1000 = 0x05 TSTANDBY_10 = 0x06 TSTANDBY_20 = 0x07 FILTER_OFF = 0x00 FILTER_2 = 0x01 FILTER_4 = 0x02 FILTER_8 = 0x03 FILTER_16 = 0x04 # and all higher class Bme280(object): # pylint: disable=bad-option-value,useless-object-inheritance def __init__(self, i2c_bus=1, sensor_address=ADDR): self.bus = smbus.SMBus(i2c_bus) self.sensor_address = sensor_address self.ho = HO_1 self.po = PO_1 self.to = TO_1 self.mode = MODE_SLEEP self.tstandy = TSTANDBY_1000 self.filter = FILTER_OFF self.read_calibration_parameters() # initialize once self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_HUM, self.get_reg_ctrl_hum()) self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_MEAS, self.get_reg_ctrl_meas()) self.bus.write_byte_data(self.sensor_address, REGISTER_CONFIG, self.get_reg_config()) def get_chip_id(self): return self.bus.read_byte_data(self.sensor_address, REGISTER_ID) def reset(self): self.bus.write_byte_data(self.sensor_address, REGISTER_RESET, 0xB6) def is_status_measuring(self): return (self.bus.read_byte_data(self.sensor_address, REGISTER_STATUS) & 0x08) != 0x00 def is_status_image_register_updating(self): return (self.bus.read_byte_data(self.sensor_address, REGISTER_STATUS) & 0x01) != 0x00 def set_humidity_oversampling(self, ho): self.ho = ho self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_HUM, self.get_reg_ctrl_hum()) # flush (unchanged) CTRL_MEAS to make CTRL_HUM effective! self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_MEAS, self.get_reg_ctrl_meas()) def get_humidity_oversampling(self): return self.ho def set_temperature_oversampling(self, to): self.to = to self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_MEAS, self.get_reg_ctrl_meas()) def get_temperature_oversampling(self): return self.to def set_pressure_oversampling(self, po): self.po = po self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_MEAS, self.get_reg_ctrl_meas()) def get_pressure_oversampling(self): return self.po def set_mode(self, mode): self.mode = mode self.bus.write_byte_data(self.sensor_address, REGISTER_CTRL_MEAS, self.get_reg_ctrl_meas()) def get_mode(self): return self.mode def set_tstandy(self, tstandy): self.tstandy = tstandy self.bus.write_byte_data(self.sensor_address, REGISTER_CONFIG, self.get_reg_config()) def get_tstandy(self): return self.tstandy def set_filter(self, fil): self.filter = fil self.bus.write_byte_data(self.sensor_address, REGISTER_CONFIG, self.get_reg_config()) def get_filter(self): return self.filter def get_data(self): if self.get_mode() == MODE_FORCED: t_measure_max = 1.25 + (2.3 * self.to) + (2.3 * self.po + 0.575) + (2.3 * self.ho + 0.575) time.sleep(t_measure_max / 1000.0) data = [] for i in range(0xF7, 0xF7 + 8): data.append(self.bus.read_byte_data(self.sensor_address, i)) pressure_raw = (data[0] << 12) | (data[1] << 4) | (data[2] >> 4) temperature_raw = (data[3] << 12) | (data[4] << 4) | (data[5] >> 4) humidity_raw = (data[6] << 8) | data[7] t_fine = self.calc_t_fine(temperature_raw) t = self.calc_compensated_temperature(t_fine) p = self.calc_compensated_pressure(t_fine, pressure_raw) h = self.calc_compensated_humidity(t_fine, humidity_raw) if self.get_mode() == MODE_FORCED: # chip returns to sleep after data readout automatically, mirror it self.mode = MODE_SLEEP return (t, p, h) def get_reg_ctrl_hum(self): """ returns the bit pattern for CTRL_HUM corresponding to the desired state of this class """ return self.ho & 0x07 def get_reg_ctrl_meas(self): """ returns the bit pattern for CTRL_MEAS corresponding to the desired state of this class """ return ((self.to & 0x07) << 5) | ((self.po & 0x07) << 2) | self.mode def get_reg_config(self): """ returns the bit pattern for CONFIG corresponding to the desired state of this class """ # SPI permanently disabled return ((self.tstandy & 0x07) << 5) | ((self.filter & 0x07) << 2) | 0x00 # Bug-fixed code, originally from https://github.com/SWITCHSCIENCE/BME280 def read_calibration_parameters(self): # read all calibration registers from chip NVM calibration_regs = [] for i in range(0x88, 0x88 + 24): calibration_regs.append(self.bus.read_byte_data(self.sensor_address, i)) calibration_regs.append(self.bus.read_byte_data(self.sensor_address, 0xA1)) for i in range(0xE1, 0xE1 + 7): calibration_regs.append(self.bus.read_byte_data(self.sensor_address, i)) # pylint: disable=bad-whitespace # reorganize 8-bit words into compensation words (without correct sign) self.digT = [] self.digT.append((calibration_regs[1] << 8) | calibration_regs[0]) self.digT.append((calibration_regs[3] << 8) | calibration_regs[2]) self.digT.append((calibration_regs[5] << 8) | calibration_regs[4]) self.digP = [] self.digP.append((calibration_regs[7] << 8) | calibration_regs[6]) self.digP.append((calibration_regs[9] << 8) | calibration_regs[8]) self.digP.append((calibration_regs[11] << 8) | calibration_regs[10]) self.digP.append((calibration_regs[13] << 8) | calibration_regs[12]) self.digP.append((calibration_regs[15] << 8) | calibration_regs[14]) self.digP.append((calibration_regs[17] << 8) | calibration_regs[16]) self.digP.append((calibration_regs[19] << 8) | calibration_regs[18]) self.digP.append((calibration_regs[21] << 8) | calibration_regs[20]) self.digP.append((calibration_regs[23] << 8) | calibration_regs[22]) self.digH = [] self.digH.append(calibration_regs[24]) self.digH.append((calibration_regs[26] << 8) | calibration_regs[25]) self.digH.append(calibration_regs[27]) self.digH.append((calibration_regs[28] << 4) | (0x0F & calibration_regs[29])) self.digH.append((calibration_regs[30] << 4) | ((calibration_regs[29] >> 4) & 0x0F)) self.digH.append(calibration_regs[31]) # fix sign for integers in two's complement for i in [1, 2]: if self.digT[i] & 0x8000: self.digT[i] = (-self.digT[i] ^ 0xFFFF) + 1 for i in [1, 2, 3, 4, 5, 6, 7, 8]: if self.digP[i] & 0x8000: self.digP[i] = (-self.digP[i] ^ 0xFFFF) + 1 for i in [1]: if self.digH[i] & 0x8000: self.digH[i] = (-self.digH[i] ^ 0xFFFF) + 1 for i in [3, 4]: if self.digH[i] & 0x0800: self.digH[i] = (-self.digH[i] ^ 0x0FFF) + 1 for i in [5]: if self.digH[i] & 0x0080: self.digH[i] = (-self.digH[i] ^ 0x00FF) + 1 # Code from Bosch datasheet translated to Python def calc_t_fine(self, adc_T): var1 = (adc_T / 16384.0 - self.digT[0] / 1024.0) * self.digT[1] var2 = (adc_T / 131072.0 - self.digT[0] / 8192.0) * (adc_T / 131072.0 - self.digT[0] / 8192.0) * self.digT[2] return var1 + var2 @staticmethod def calc_compensated_temperature(t_fine): return t_fine / 5120.0 def calc_compensated_pressure(self, t_fine, adc_P): var1 = (t_fine / 2.0) - 64000.0 var2 = var1 * var1 * (self.digP[5]) / 32768.0 var2 = var2 + var1 * (self.digP[4]) * 2.0 var2 = (var2 / 4.0) + (self.digP[3] * 65536.0) var1 = (self.digP[2] * var1 * var1 / 524288.0 + self.digP[1] * var1) / 524288.0 var1 = (1.0 + var1 / 32768.0) * self.digP[0] if var1 == 0.0: return 0 # avoid exception caused by division by zero p = 1048576.0 - adc_P p = (p - (var2 / 4096.0)) * 6250.0 / var1 var1 = self.digP[8] * p * p / 2147483648.0 var2 = p * self.digP[7] / 32768.0 return p + (var1 + var2 + self.digP[6]) / 16.0 def calc_compensated_humidity(self, t_fine, adc_H): var_H = t_fine - 76800.0 # yapf: disable # pylint: disable=line-too-long var_H = (adc_H - (self.digH[3] * 64.0 + self.digH[4] / 16384.0 * var_H)) * (self.digH[1] / 65536.0 * (1.0 + self.digH[5] / 67108864.0 * var_H * (1.0 + self.digH[2] / 67108864.0 * var_H))) # yapf: enable var_H = var_H * (1.0 - self.digH[0] * var_H / 524288.0) if var_H > 100.0: var_H = 100.0 elif var_H < 0.0: var_H = 0.0 return var_H