# Christian Fiot Nov 2020 # temperature, humidity, pressure sensors # power requirement 3.6uA max # # from BME280 from BMP280 # same functionality with added humidity sensor # 2.00 # # Usage: # from BME280 import BME280 # # Bar = BME280(0x76, traceDebug=True) # Bar.begin() # return True if chip found # Bar.read() # return T in C and P in Pa # Bar.Convert_C2F(n) # Bar.Convert_Pa2PSI(n) # # Credit https://github.com/pimoroni/bme280-python/blob/master/library/bme280/__init__.py # Credit https://github.com/ButchAnton/LoPy_BME280/blob/master/bme280.py # REG_CHIPID = 0xD0 # = 0x060 # REG_SOFTRESET = 0xE0 # REG_STATUS = 0xF3 # REG_CONTROL = 0xF4 # REG_CONFIG = 0xF5 # REG_PRESSURE_DATA = 0xF7 # F7[2] F8[1] F9[0] # REG_TEMP_DATA = 0xFA # FA[2] FB[1] FC[0] from trap import * # 2.2.9b from machine import I2C # 2.2.18 class BME280(): def __init__(self, iicadr=0x076, i2c=None, sda='P22', scl='P21', traceDebug=False, sdAccess=False): # 2.2.9b self.trace = traceDebug self.adr = iicadr self.sdAccess = sdAccess # 2.2.9b # 2.2.21 self.temperature = 0 self.temperature_fine = 0 self.tempDAC = 0 # DAC equivalent self.pressure = 0 self.presDAC = 0 self.humidity = 0 self.humDAC = 0 # Section 3.12 These coefficient are used to test compensate _temperature() _pressure() pg #23 BMP280 self.CoeffData = bytearray(26) # 2.00 bytearray(12*2) self.dig_t1 = 27504 # U 0x88 0x89 self.dig_t2 = 26435 # S 0x8A 0x8B self.dig_t3 = -1000 # S 0x8C 0x8D self.dig_p1 = 36477 # U 0x8E 0x8F self.dig_p2 = -10685 # S 0x90 0x91 self.dig_p3 = 3024 # S 0x92 0x93 self.dig_p4 = 2855 # S 0x94 0x95 self.dig_p5 = 140 # S 0x96 0x97 self.dig_p6 = -7 # S 0x98 0x99 self.dig_p7 = 15500 # S 0x9A 0x9B self.dig_p8 = -14600 # S 0x9C 0x9D self.dig_p9 = 6000 # S 0x9E 0x9F self.dig_h1 = 75 # 2.00 U 0x0A1 # 2.00 self.CoeffHData = bytearray(7) self.dig_h2 = 376 # S 0x0E1 0x0E2 self.dig_h3 = 0 # U 0x0E3 self.dig_h4 = 286 # S 0x0E4 0x0E5 self.dig_h5 = 50 # 0x0E5 0x0E6 self.dig_h6 = 30 # 0x0E7 # I2C bus declaration is extenal # MCP are connected on I2C bus #1 SDA-P22 SCL-P21 # I2C bus #2 SDA-P18 SCL-P17 # if i2c is not None: # 2.2.18 self.i2c1 = i2c else: # from machine import I2C self.i2c1 = I2C(0, mode=I2C.MASTER, pins=(sda, scl)) # fetch the calibration coefficients from CoeffData buffer def getCoeffU16(self, pointer): result = (self.CoeffData[pointer+1] << 8) | self.CoeffData[pointer] if self.trace : print('Upointer {:2}: {}'.format (pointer, result) ) return result def getCoeffS16(self, pointer): result = (self.CoeffData[pointer+1] << 8) | self.CoeffData[pointer] if result > 32767: result -= 65536 if self.trace : print('Spointer {:2}: {}'.format (pointer, result) ) return result # Section 3.12 These coefficient are used to test compensate _temperature() _pressure() # read calibration data, used to format temperature and pressure # carreful to the bytes order see page#23 of the datasheet def getCalibCoeff(self): self.i2c1.readfrom_mem_into(self.adr, 0x88, self.CoeffData) # return self.CoeffData if self.trace: print("CoeffData: $") # + str(self.CoeffData) ) for i in self.CoeffData: print(" %X," % i, end = "") print("") self.dig_t1 = self.getCoeffU16(0) # U 0x88 0x89 self.dig_t2 = self.getCoeffS16(2) # S 0x8A 0x8B self.dig_t3 = self.getCoeffS16(4) # S 0x8C 0x8D self.dig_p1 = self.getCoeffU16(6) # U 0x8E 0x8F self.dig_p2 = self.getCoeffS16(8) # S 0x90 0x91 self.dig_p3 = self.getCoeffS16(10) # S 0x92 0x93 self.dig_p4 = self.getCoeffS16(12) # S 0x94 0x95 self.dig_p5 = self.getCoeffS16(14) # S 0x96 0x97 self.dig_p6 = self.getCoeffS16(16) # S 0x98 0x99 self.dig_p7 = self.getCoeffS16(18) # S 0x9A 0x9B self.dig_p8 = self.getCoeffS16(20) # S 0x9C 0x9D self.dig_p9 = self.getCoeffS16(22) # S 0x9E 0x9F self.dig_h1 = self.getCoeffU16(24) >> 8 # 2.00 keep $A1 only # 2.00 self.i2c1.readfrom_mem_into(self.adr, 0xE1, self.CoeffHData) if self.trace: print("CoeffHData: $") # + str(self.CoeffHData) ) for i in self.CoeffHData: print(" %X," % i, end = "") print("") self.dig_h2 = self.CoeffHData[0] | ( self.CoeffHData[1] << 8) self.dig_h3 = self.CoeffHData[2] self.dig_h4 = (self.CoeffHData[4] & 0x0F) | (self.CoeffHData[3] << 4) self.dig_h5 = ((self.CoeffHData[4] & 0x0F0) >> 4) | (self.CoeffHData[5] << 4 ) self.dig_h6 = self.CoeffHData[6] if self.trace: print("dig_h2: $%X %d" % (self.dig_h2, self.dig_h2)) print("dig_h3: $%X %d" % (self.dig_h3, self.dig_h3)) print("dig_h4: $%X %d" % (self.dig_h4, self.dig_h4)) print("dig_h5: $%X %d" % (self.dig_h5, self.dig_h5)) print("dig_h6: $%X %d" % (self.dig_h6, self.dig_h6)) # Detect and init sensor def begin(self): int = 0 # 2.2.9b try: did = self.i2c1.readfrom_mem(self.adr, 0xD0,1) int = did[0] if self.trace : print("Read device ID:" + str(did[0])) print("Fetch calibration coefficients:") # read calibration coefficient to correct raw data self.getCalibCoeff() # 2.00 Write to humidity ctrl # ovsmp = 2 osrs_h[2:0]= 010 self.i2c1.writeto_mem(self.adr, 0xF2, bytes([0b010])) # 4.3.4 Write to REG_CONTROL # pressure ovsmp = 2 reso 1.31 Pa osrs_p[7:5]= 010 # temperature ovsmp = 2 reso 0.0025 C osrs_t[4:2]= 010 # Power mode normal b[1:0]= 11 self.i2c1.writeto_mem(self.adr, 0xF4, bytes([0b01001011])) # configurate the sensor # 4.3.5 Write to REG_CONFIG # Stanby 250ms t_sb[7:5]= 011 # IIR filter 4 filter[4:2]= 010 # interface I2C [1:0]= 00 self.i2c1.writeto_mem(self.adr, 0xF5, bytes([0b01101000])) print('Detected BME280 - Temp/Humidity/Pressure Sensor Adr:' + str(self.adr) ) except Exception as e: # 2.2.9b scratch = 'BME280 - Temp/Humidity/Pressure Sensor (Adr:' + str(self.adr) + ') not found - ' # 2.2.9b print('BME280 - Temp/Humidity/Pressure Sensor (Adr:' + str(self.adr) + ') not found.') file_errLog(0, scratch + str(e), self.sdAccess) # 2.2.9b # 2.2.18 print('Begin I2C1 scan ...') # 2.2.18 print(self.i2c1.scan()) int = 0 finally: return int == 0x060 # Section 3.12 checked, 519888 => 25.08248 C def compensate_temperature(self, raw_temperature): var1 = (raw_temperature / 16384.0 - self.dig_t1 / 1024.0) * self.dig_t2 var2 = raw_temperature / 131072.0 - self.dig_t1 / 8192.0 var2 = var2 * var2 * self.dig_t3 self.temperature_fine = (var1 + var2) self.temperature = self.temperature_fine / 5120.0 # if (self.temperature != 0): # self.temperature = round(self.temperature, 2) # Section 3.12 checked, 415148 => 100653.3 Pa def compensate_pressure(self, raw_pressure): var1 = self.temperature_fine / 2.0 - 64000.0 var2 = var1 * var1 * self.dig_p6 / 32768.0 var2 = var2 + var1 * self.dig_p5 * 2 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 pressure = 1048576.0 - raw_pressure pressure = (pressure - var2 / 4096.0) * 6250.0 / var1 var1 = self.dig_p9 * pressure * pressure / 2147483648.0 var2 = pressure * self.dig_p8 / 32768.0 self.pressure = pressure + (var1 + var2 + self.dig_p7) / 16.0 # self.pressure = round(self.pressure + 0.001, 2) # 2.00 # check 30281 => 68.66996648709039 def compensate_humidity(self, raw_humidity): var1 = self.temperature_fine - 76800.0 var2 = self.dig_h4 * 64.0 + (self.dig_h5 / 16384.0) * var1 var3 = raw_humidity - var2 var4 = self.dig_h2 / 65536.0 var5 = 1.0 + (self.dig_h3 / 67108864.0) * var1 var6 = 1.0 + (self.dig_h6 / 67108864.0) * var1 * var5 var6 = var3 * var4 * (var5 * var6) self.humidity = var6 * (1.0 - self.dig_h1 * var6 / 524288.0) def Convert_C2F(self, DataC): return (DataC * 9/5) + 32 def Convert_Pa2PSI(self, DataPa): return DataPa / 6895 def Convert_Pa2ATM(self, DataPa): # 1.15 return DataPa / 101325 # see datasheet section 3.9 Data readout def read(self): uTuPData = bytearray(6+2) # 2.00 3*2) self.i2c1.readfrom_mem_into(self.adr, 0xF7, uTuPData) pres = ( (uTuPData[0] << 16) | (uTuPData[1] << 8) | uTuPData[2] ) >> 4 temp = ( (uTuPData[3] << 16) | (uTuPData[4] << 8) | uTuPData[5] ) >> 4 hum = (uTuPData[6] << 8) | (uTuPData[7]) # 2.00 # 2.2.21 to detect sensor reset ... self.tempDAC = temp self.presDAC = pres self.humDAC = hum # Must compute temperature first then pressure self.compensate_temperature(temp) self.compensate_pressure(pres) self.compensate_humidity(hum) # 2.00 if self.trace : print("Temp C: " + str(self.temperature) + " F: " + str(self.Convert_C2F(self.temperature))) print("Pres Pa: " + str(self.pressure) + " PSI: " + str(self.Convert_Pa2PSI(self.pressure))) print("Hum RH: " + str(self.humidity) ) # 2.00 # return uTuPData # return temp, pres return self.temperature, self.pressure, self.humidity # Temp in C, Pressure in Pa, Humidity %RH