BME280 on Pi Zero: Log Temperature, Humidity and Pressure to CSV

#!/usr/bin/env python3
"""Log BME280 temperature, humidity and pressure to a CSV file.

Run:  ~/envs/sensors/bin/python bme280_logger.py
"""
import csv
import os
import time
from datetime import datetime

import bme280   # provided by the RPi.bme280 package
import smbus2

I2C_BUS = 1            # the 40-pin header uses I2C bus 1
ADDRESS = 0x76         # change to 0x77 if i2cdetect showed 77
INTERVAL_S = 60        # seconds between readings
CSV_PATH = os.path.expanduser('~/bme280_log.csv')

bus = smbus2.SMBus(I2C_BUS)
# Read the sensor's calibration data once at startup
calibration = bme280.load_calibration_params(bus, ADDRESS)

def read_sensor():
    """Take one compensated sample and return rounded values."""
    data = bme280.sample(bus, ADDRESS, calibration)
    return (round(data.temperature, 2),   # degrees Celsius
            round(data.humidity, 1),      # percent relative humidity
            round(data.pressure, 2))      # hPa

def main():
    new_file = not os.path.exists(CSV_PATH)
    # newline='' prevents blank lines on some platforms; buffering=1 = line buffered
    with open(CSV_PATH, 'a', newline='', buffering=1) as f:
        writer = csv.writer(f)
        if new_file:
            writer.writerow(['timestamp', 'temperature_c', 'humidity_pct', 'pressure_hpa'])
        while True:
            try:
                temp, hum, pres = read_sensor()
                stamp = datetime.now().isoformat(timespec='seconds')
                writer.writerow([stamp, temp, hum, pres])
                print(stamp, temp, 'C', hum, '%', pres, 'hPa')
            except OSError as err:
                # A loose wire gives an I/O error; log it and keep running
                print('Read failed:', err)
            time.sleep(INTERVAL_S)

if __name__ == '__main__':
    try:
        main()
    except KeyboardInterrupt:
        print('Stopped')
    finally:
        bus.close()