173 lines
4.9 KiB
Python
Executable File
173 lines
4.9 KiB
Python
Executable File
#!/usr/bin/python
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#--------------------------------------
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# ___ ___ _ ____
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# / _ \/ _ \(_) __/__ __ __
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# / , _/ ___/ /\ \/ _ \/ // /
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# /_/|_/_/ /_/___/ .__/\_, /
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# /_/ /___/
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#
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# bme280.py
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# Read data from a digital pressure sensor.
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#
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# Official datasheet available from :
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# https://www.bosch-sensortec.com/bst/products/all_products/bme280
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#
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# Author : Matt Hawkins
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# Date : 21/01/2018
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#
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# https://www.raspberrypi-spy.co.uk/
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#
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#--------------------------------------
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import smbus
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import time
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from ctypes import c_short
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from ctypes import c_byte
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from ctypes import c_ubyte
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DEVICE = 0x76 # Default device I2C address
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bus = smbus.SMBus(1) # Rev 2 Pi, Pi 2 & Pi 3 uses bus 1
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# Rev 1 Pi uses bus 0
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def getShort(data, index):
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# return two bytes from data as a signed 16-bit value
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return c_short((data[index+1] << 8) + data[index]).value
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def getUShort(data, index):
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# return two bytes from data as an unsigned 16-bit value
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return (data[index+1] << 8) + data[index]
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def getChar(data,index):
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# return one byte from data as a signed char
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result = data[index]
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if result > 127:
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result -= 256
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return result
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def getUChar(data,index):
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# return one byte from data as an unsigned char
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result = data[index] & 0xFF
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return result
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def readBME280ID(addr=DEVICE):
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# Chip ID Register Address
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REG_ID = 0xD0
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(chip_id, chip_version) = bus.read_i2c_block_data(addr, REG_ID, 2)
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return (chip_id, chip_version)
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def readBME280All(addr=DEVICE):
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# Register Addresses
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REG_DATA = 0xF7
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REG_CONTROL = 0xF4
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REG_CONFIG = 0xF5
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REG_CONTROL_HUM = 0xF2
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REG_HUM_MSB = 0xFD
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REG_HUM_LSB = 0xFE
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# Oversample setting - page 27
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OVERSAMPLE_TEMP = 2
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OVERSAMPLE_PRES = 2
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MODE = 1
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# Oversample setting for humidity register - page 26
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OVERSAMPLE_HUM = 2
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bus.write_byte_data(addr, REG_CONTROL_HUM, OVERSAMPLE_HUM)
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control = OVERSAMPLE_TEMP<<5 | OVERSAMPLE_PRES<<2 | MODE
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bus.write_byte_data(addr, REG_CONTROL, control)
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# Read blocks of calibration data from EEPROM
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# See Page 22 data sheet
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cal1 = bus.read_i2c_block_data(addr, 0x88, 24)
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cal2 = bus.read_i2c_block_data(addr, 0xA1, 1)
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cal3 = bus.read_i2c_block_data(addr, 0xE1, 7)
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# Convert byte data to word values
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dig_T1 = getUShort(cal1, 0)
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dig_T2 = getShort(cal1, 2)
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dig_T3 = getShort(cal1, 4)
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dig_P1 = getUShort(cal1, 6)
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dig_P2 = getShort(cal1, 8)
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dig_P3 = getShort(cal1, 10)
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dig_P4 = getShort(cal1, 12)
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dig_P5 = getShort(cal1, 14)
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dig_P6 = getShort(cal1, 16)
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dig_P7 = getShort(cal1, 18)
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dig_P8 = getShort(cal1, 20)
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dig_P9 = getShort(cal1, 22)
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dig_H1 = getUChar(cal2, 0)
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dig_H2 = getShort(cal3, 0)
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dig_H3 = getUChar(cal3, 2)
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dig_H4 = getChar(cal3, 3)
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dig_H4 = (dig_H4 << 24) >> 20
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dig_H4 = dig_H4 | (getChar(cal3, 4) & 0x0F)
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dig_H5 = getChar(cal3, 5)
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dig_H5 = (dig_H5 << 24) >> 20
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dig_H5 = dig_H5 | (getUChar(cal3, 4) >> 4 & 0x0F)
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dig_H6 = getChar(cal3, 6)
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# Wait in ms (Datasheet Appendix B: Measurement time and current calculation)
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wait_time = 1.25 + (2.3 * OVERSAMPLE_TEMP) + ((2.3 * OVERSAMPLE_PRES) + 0.575) + ((2.3 * OVERSAMPLE_HUM)+0.575)
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time.sleep(wait_time/1000) # Wait the required time
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# Read temperature/pressure/humidity
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data = bus.read_i2c_block_data(addr, REG_DATA, 8)
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pres_raw = (data[0] << 12) | (data[1] << 4) | (data[2] >> 4)
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temp_raw = (data[3] << 12) | (data[4] << 4) | (data[5] >> 4)
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hum_raw = (data[6] << 8) | data[7]
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#Refine temperature
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var1 = ((((temp_raw>>3)-(dig_T1<<1)))*(dig_T2)) >> 11
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var2 = (((((temp_raw>>4) - (dig_T1)) * ((temp_raw>>4) - (dig_T1))) >> 12) * (dig_T3)) >> 14
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t_fine = var1+var2
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temperature = float(((t_fine * 5) + 128) >> 8);
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# Refine pressure and adjust for temperature
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var1 = t_fine / 2.0 - 64000.0
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var2 = var1 * var1 * dig_P6 / 32768.0
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var2 = var2 + var1 * dig_P5 * 2.0
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var2 = var2 / 4.0 + dig_P4 * 65536.0
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var1 = (dig_P3 * var1 * var1 / 524288.0 + dig_P2 * var1) / 524288.0
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var1 = (1.0 + var1 / 32768.0) * dig_P1
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if var1 == 0:
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pressure=0
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else:
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pressure = 1048576.0 - pres_raw
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pressure = ((pressure - var2 / 4096.0) * 6250.0) / var1
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var1 = dig_P9 * pressure * pressure / 2147483648.0
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var2 = pressure * dig_P8 / 32768.0
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pressure = pressure + (var1 + var2 + dig_P7) / 16.0
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# Refine humidity
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humidity = t_fine - 76800.0
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humidity = (hum_raw - (dig_H4 * 64.0 + dig_H5 / 16384.0 * humidity)) * (dig_H2 / 65536.0 * (1.0 + dig_H6 / 67108864.0 * humidity * (1.0 + dig_H3 / 67108864.0 * humidity)))
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humidity = humidity * (1.0 - dig_H1 * humidity / 524288.0)
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if humidity > 100:
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humidity = 100
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elif humidity < 0:
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humidity = 0
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return temperature/100.0,pressure/100.0,humidity
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def main():
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(chip_id, chip_version) = readBME280ID()
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print "Chip ID:", chip_id
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print "Version:", chip_version
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temperature,pressure,humidity = readBME280All()
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print "Temperature:", temperature
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print "Pressure:", pressure
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print "Humidity:", humidity
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if __name__=="__main__":
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main()
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