compensated_temp.py

#!/usr/bin/env python3

import time
from bme280 import BME280

try:
    from smbus2 import SMBus
except ImportError:
    from smbus import SMBus

import logging


# Tuning factor for compensation. Decrease this number to adjust the
# temperature down, and increase to adjust up
factor = 2.25

# Get the temperature of the CPU for compensation
def get_cpu_temperature():
    with open("/sys/class/thermal/thermal_zone0/temp", "r") as f:
        temp = f.read()
        temp = int(temp) / 1000.0
    return temp


if __name__ == "__main__":
    logging.basicConfig(
        format='%(asctime)s.%(msecs)03d %(levelname)-8s %(message)s',
        level=logging.INFO,
        datefmt='%Y-%m-%d %H:%M:%S')

    logging.info("""compensated-temperature.py - Use the CPU temperature
    to compensate temperature readings from the BME280 sensor.
    Method adapted from Initial State's Enviro pHAT review:
    https://medium.com/@InitialState/tutorial-review-enviro-phat-for-raspberry-pi-4cd6d8c63441

    Press Ctrl+C to exit!

    """)

    bus = SMBus(1)
    bme280 = BME280(i2c_dev=bus)


    cpu_temps = [get_cpu_temperature()] * 5

    while True:
        cpu_temp = get_cpu_temperature()
        # Smooth out with some averaging to decrease jitter
        cpu_temps = cpu_temps[1:] + [cpu_temp]
        avg_cpu_temp = sum(cpu_temps) / float(len(cpu_temps))
        raw_temp = bme280.get_temperature()
        comp_temp = raw_temp - ((avg_cpu_temp - raw_temp) / factor)
        comp_temp_f = (comp_temp * 9 / 5) + 32
        logging.info("Compensated temperature: {:05.2f} *F".format(comp_temp_f))
        time.sleep(1.0)