Added user projects section to README

[EVA-2020-02-2.git] / examples / compensated-temperature.py

diff --git a/examples/compensated-temperature.py b/examples/compensated-temperature.py
index 87daf97896b76e6bfdb92bcafb64e62ec48e18e2..b648f57608a02c5a8a523b90a88884d545dac979 100755 (executable)
--- a/examples/compensated-temperature.py
+++ b/examples/compensated-temperature.py
@@ -1,17 +1,24 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import time
 from bme280 import BME280
-from subprocess import PIPE, Popen
 
 try:
     from smbus2 import SMBus
 except ImportError:
     from smbus import SMBus
 
-print("""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
+import logging
+
+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!
 
@@ -20,16 +27,27 @@ 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():
-    process = Popen(['vcgencmd', 'measure_temp'], stdout=PIPE)
-    output, _error = process.communicate()
-    return float(output[output.index('=') + 1:output.rindex("'")])
+    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
 
-factor = 0.6
+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 - ((cpu_temp - raw_temp) / factor)
-    print("Compensated temperature: {:05.2f} *C".format(comp_temp))
+    comp_temp = raw_temp - ((avg_cpu_temp - raw_temp) / factor)
+    logging.info("Compensated temperature: {:05.2f} *C".format(comp_temp))
     time.sleep(1.0)