First working code for HC-SR04 sensor.

hcsr04_funcs.py

@@ -0,0 +1,34 @@
+import time
+
+'''
+hcsr04_funcs: Helper functions to interact with the HC-SR04 sensor.
+'''
+
+def read_hc_sr04(trig, echo):
+    """
+        reads the HC-SR04 sensor.
+        returns tuple(temperature, humidity) if no errors
+        returns None if there was an error
+    """
+    try:
+        trig.value(0)
+        time.sleep(0.1)
+         
+        trig.value(1)
+        time.sleep_us(2)
+        
+        trig.value(0)
+        
+        while echo.value()==0:
+             pulse_start = time.ticks_us()
+        
+        while echo.value()==1:
+             pulse_end = time.ticks_us()
+        
+        pulse_duration = pulse_end - pulse_start
+        distance = pulse_duration * 17165 / 1000000
+        distance = round(distance, 2)
+        
+        return distance
+    except:
+        return None