From 964011e832e8ee9c971efd5da8f011f76885ff27 Mon Sep 17 00:00:00 2001
From: Martin Kompf <skaringa@nospam.org>
Date: Sun, 10 Feb 2019 17:00:06 +0100
Subject: [PATCH] Simplified low pass filter

---
 arduino_sketch/ReflectorLightBarrier.ino | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arduino_sketch/ReflectorLightBarrier.ino b/arduino_sketch/ReflectorLightBarrier.ino
index 65356a8..334c24a 100644
--- a/arduino_sketch/ReflectorLightBarrier.ino
+++ b/arduino_sketch/ReflectorLightBarrier.ino
@@ -33,10 +33,9 @@ int sensorValue = 0; // difference sensorValueOn - sensorValueOff
 float filteredValue; // filtered sensor value
 
 // definitions for low pass filter
-#define FILTER_LEN 6
-float buffer[FILTER_LEN];
-int startBuf = 0;
-int lenBuf = 0;
+float filterAlpha = 0.1f;
+float filterOut = 0;
+boolean filterLoad = true;
 
 // command line
 #define MAX_CMD_LEN 80
@@ -175,20 +174,15 @@ void doCommand() {
  * Low pass filter to eleminate spikes
  */
 float lowpass(int value) {
-  if (lenBuf < FILTER_LEN) {
-    lenBuf++;
+  if (filterLoad) {
+    filterOut = value;
+    filterLoad = false;
   }
-  buffer[startBuf++] = (float) value;
-  if (startBuf >= FILTER_LEN) {
-    startBuf = 0;
-  }
-  float sum = 0;
-  for (int i = 0; i < lenBuf; ++i) {
-    sum += buffer[i];
-  }
-  return sum / lenBuf;
+  filterOut = filterAlpha * value + (1.f - filterAlpha) * filterOut;
+  return filterOut;
 }
 
+
 /**
  * Setup.
  */