Update README install instructions

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

diff --git a/examples/compensated-temperature.py b/examples/compensated-temperature.py
index 64d7a8b9bed07c020f62fd570c011be2d22989cc..048eb804fde2096a7c170bef086a94d8258ec4d0 100755 (executable)
--- a/examples/compensated-temperature.py
+++ b/examples/compensated-temperature.py
@@ -9,9 +9,10 @@ try:
 except ImportError:
     from smbus 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
+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!
 
 
 Press Ctrl+C to exit!
 


@@ -20,16 +21,27 @@ Press Ctrl+C to exit!
 bus = SMBus(1)
 bme280 = BME280(i2c_dev=bus)
 
 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()
 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("'")])
 
     return float(output[output.index('=') + 1:output.rindex("'")])
 

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

 factor = 0.8
 
 factor = 0.8
 

+cpu_temps = [0] * 5
+

 while True:
     cpu_temp = get_cpu_temperature()
 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()
     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)
     print("Compensated temperature: {:05.2f} *C".format(comp_temp))
     time.sleep(1.0)