Here is my version. Let me know if you find any issue. Otherwise have fun!
Here is the work flow:
-Take 10 readings at a time into an arraylist
-Sort the arraylist asc order
-Then eliminate low/high extreme values.
-Then I avg the middle 6 values. If the avg is out of manufacture’s specs return min or max respectively.
//-------------------------------------------------------------------------------------
// GHI Electronics, LLC
// Copyright (c) 2009
// All rights reserved
//-------------------------------------------------------------------------------------
// Modifications:
//-------------------------------------------------------------------------------------
// Hai Nguyen
// 09/2010 Added GetDistanceCmWithFilter() and quickSort() in attempt to
// eliminate possible invalid readings
//
//-------------------------------------------------------------------------------------
/*
* You can use this file if you agree to the following:
*
* 1. This header can't be changed under any condition.
*
* 2. This is a free software and therefore is provided with NO warranty.
*
* 3. Feel free to modify the code but we ask you to provide us with
* any bugs reports so we can keep the code up to date.
*
* 4. This code may ONLY be used with GHI Electronics, LLC products.
*
* THIS SOFTWARE IS PROVIDED BY GHI ELECTRONICS, LLC ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
* GHI ELECTRONICS, LLC BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR ORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* Specs are subject to change without any notice
*/
using System;
using System.Threading;
using Microsoft.SPOT;
using Microsoft.SPOT.Hardware;
using GHIElectronics.NETMF.Hardware;
using GHIElectronics.NETMF.FEZ;
namespace GHIElectronics.NETMF.FEZ
{
public static partial class FEZ_Components
{
public class DistanceDetector : IDisposable
{
AnalogIn adc;
float Y0 = 0;
float X0 = 0;
float Y1 = 0;
float X1 = 0;
float C = 0;
public enum SharpSensorType : byte
{
GP2Y0A21YK = 0,
GP2D120 = 1,
}
public void Dispose()
{
adc.Dispose();
}
public DistanceDetector(FEZ_Pin.AnalogIn pin, SharpSensorType type)
{
adc = new AnalogIn((AnalogIn.Pin)pin);
adc.SetLinearScale(0, 330);
switch (type)
{
case SharpSensorType.GP2Y0A21YK:
Y0 = 10;
X0 = 315;
Y1 = 80;
X1 = 30;
break;
case SharpSensorType.GP2D120:
Y0 = 3;
X0 = 315;
Y1 = 30;
X1 = 30;
break;
}
C = (Y1 - Y0) / (1 / X1 - 1 / X0);
}
public float GetDistance_cm()
{
return C / ((float)adc.Read() + (float).001) - (C / X0) + Y0;
}
public float GetDistanceCmWithFilter()
{
const int ARRAY_SIZE = 10;
float[] array2Sort = new float[ARRAY_SIZE];
//make 10 readings
for (int i = 0; i < ARRAY_SIZE; i++)
array2Sort[i] = GetDistance_cm();
//sort the values in ascending order
quickSort(0, ARRAY_SIZE - 1, ref array2Sort);
//elimate lowest extremes and highest extremes. calculate avg for the middle 6 values
float avg = 0;
for (int i = 2; i < 8; i++)
avg += array2Sort[i];
avg = avg / 6;
//check for valid ranges within manufacture's specs.
if (avg < Y0) return Y0;
if (avg > Y1) return Y1;
return avg;
}
public void quickSort(int left, int right, ref float[] array2Sort)
{
int leftHolder = left;
int rightHolder = right;
float pivot = array2Sort[left];
while( left < right )
{
while( (array2Sort[right] >= pivot) && (left < right) )
right--;
if( left != right ) {
array2Sort[left] = array2Sort[right];
left++;
}
while( (array2Sort[left] <= pivot) && (left < right) )
left++;
if( left != right ) {
array2Sort[right] = array2Sort[left];
right--;
}
}
array2Sort[left] = pivot;
pivot = left;
left = leftHolder;
right = rightHolder;
if (left < pivot) quickSort(left, (int)pivot - 1, ref array2Sort);
if (right > pivot) quickSort((int)pivot + 1, right, ref array2Sort);
}
}//quickSort
}
}
My class implements pretty much everything you have there except mfr specs, however my culling of variables outside of range is done with standard deviation so you only end up with middle values and culling if it’s needed.