examples/compensated-temperature.py

   1 #!/usr/bin/env python
   2
   3 import time
   4 from bme280 import BME280
   5 from subprocess import PIPE, Popen
   6
   7 try:
   8     from smbus2 import SMBus
   9 except ImportError:
  10     from smbus import SMBus
  11
  12 print("""compensated-temperature.py - Use the CPU temperature to compensate temperature
  13 readings from the BME280 sensor. Method adapted from Initial State's Enviro pHAT
  14 review: https://medium.com/@InitialState/tutorial-review-enviro-phat-for-raspberry-pi-4cd6d8c63441
  15
  16 Press Ctrl+C to exit!
  17
  18 """)
  19
  20 bus = SMBus(1)
  21 bme280 = BME280(i2c_dev=bus)
  22
  23 def get_cpu_temperature():
  24     process = Popen(['vcgencmd', 'measure_temp'], stdout=PIPE)
  25     output, _error = process.communicate()
  26     return float(output[output.index('=') + 1:output.rindex("'")])
  27
  28 factor = 0.6
  29
  30 while True:
  31     cpu_temp = get_cpu_temperature()
  32     raw_temp = bme280.get_temperature()
  33     comp_temp = raw_temp - ((cpu_temp - raw_temp) / factor)
  34     print("Compensated temperature: {:05.2f} *C".format(comp_temp))
  35     time.sleep(1.0)