X-Git-Url: https://zdv2.bktei.com/gitweb/EVA-2020-02-2.git/blobdiff_plain/a155e335d1f16716fe7c8a80491773a450c10fed..a862bb9473fbe8ec4a3b62d1e9b6f7a967b337ee:/examples/compensated-temperature.py?ds=inline

diff --git a/examples/compensated-temperature.py b/examples/compensated-temperature.py
index 87daf97..048eb80 100755
--- a/examples/compensated-temperature.py
+++ b/examples/compensated-temperature.py
@@ -9,9 +9,10 @@ try:
 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
+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
 
 Press Ctrl+C to exit!
 
@@ -20,16 +21,27 @@ 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()
+    output = output.decode()
     return float(output[output.index('=') + 1:output.rindex("'")])
 
-factor = 0.6
+
+# Tuning factor for compensation. Decrease this number to adjust the
+# temperature down, and increase to adjust up
+factor = 0.8
+
+cpu_temps = [0] * 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)
+    comp_temp = raw_temp - ((avg_cpu_temp - raw_temp) / factor)
     print("Compensated temperature: {:05.2f} *C".format(comp_temp))
     time.sleep(1.0)