Decodes the current state of a quadrature encoder from raw A/B channels

QuadratureCounter.cs

using Bonsai;
using System;
using System.ComponentModel;
using System.Collections.Generic;
using System.Linq;
using System.Reactive.Linq;

[Combinator]
[Description("Decodes the current state of a quadrature encoder from raw A/B channels.")]
[WorkflowElementCategory(ElementCategory.Transform)]
public class QuadratureCounter
{
    public QuadratureCounter()
    {
        Threshold = 2.5f;
    }

    public float Threshold { get; set; }

    public IObservable<int> Process(IObservable<float[]> source)
    {
        return Observable.Defer(() =>
        {
            int counter = 0;
            return source.Select(input =>
            {
                var inputA = new float[input.Length / 2];
                var inputB = new float[input.Length / 2];
                Array.Copy(input, 0, inputA, 0, inputA.Length);
                Array.Copy(input, inputA.Length, inputB, 0, inputB.Length);

                var first = true;
                var prevA = false;
                var prevB = false;
                var direction = 0;
                for (int i = 0; i < inputA.Length; i++)
                {
                    var a = inputA[i] > Threshold ? true : false;
                    var b = inputB[i] > Threshold ? true : false;
                    var changeA = a != prevA;
                    var changeB = b != prevB;
                    if (first) first = false;
                    else if (changeA || changeB)
                    {
                        if (prevA == prevB) direction = changeB ? 1 : -1;
                        else direction = changeA ? 1 : -1;
                        counter += direction;
                    }
                    prevA = a;
                    prevB = b;
                }

                return counter;
            });
        });
    }
}