Added first order filter to distance measurement to reduce noise.

main.py

@@ -1,14 +1,11 @@
-# Built-in's
 import network
 import rp2
 import time
 import json
 import machine
-
-# From PyPI
+from machine import Pin
 from umqtt.robust import MQTTClient
-
-# From this project...
+import wifi_config
 import mqtt_config
 from pico_funcs import read_cpu_temp, wlan_up, led_error_code
 from hcsr04_funcs import read_hc_sr04
@@ -43,13 +40,17 @@ def main():
         )
 
     # Create HC-SR04
-    trig = machine.Pin(TRIG_PIN, machine.Pin.OUT)
-    echo = machine.Pin(ECHO_PIN, machine.Pin.IN, machine.Pin.PULL_DOWN)
+    trig = Pin(TRIG_PIN, Pin.OUT)
+    echo = Pin(ECHO_PIN, Pin.IN, Pin.PULL_DOWN)
     
     # Let's Go!
     if DEBUG:
         print("Enter main loop")
 
+    # First Time flag allows the 1st order filter to be initialized.
+    first_time = True
+    FILTER_CONSTANT = 0.9
+    
     while True:
 
         # Loop Clean-Up and Prep
@@ -71,7 +72,12 @@ def main():
 
         # HC-SR04 Reading.
         try:
-            distance = read_hc_sr04(trig, echo)
+            sensor_value = read_hc_sr04(trig, echo)
+            if not first_time:
+                distance = distance * FILTER_CONSTANT + (1 - FILTER_CONSTANT) * sensor_value
+            else:
+                distance = sensor_value
+                first_time = False
             hc_sr04_ready = True
         except:
             continue