#!/usr/bin/env python3

import logging

import time

from bme280 import BME280

from smbus2 import SMBus

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)

# 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

# Tuning factor for compensation. Decrease this number to adjust the

# temperature down, and increase to adjust up

factor = 2.25

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)

logging.info(f"Compensated temperature: {comp_temp:05.2f} °C")

time.sleep(1.0)