File content as of revision 3:531a74cecb89:

float lowPass(float sample)
{
    static const float a[4] = {1.00000000e+00,-2.77555756e-16,3.33333333e-01,-1.85037171e-17};
    static const float b[4] = {0.16666667,0.5,0.5,0.16666667};
// x array for holding recent inputs (newest input as index 0, delay of 1 at index 1, etc.
    static volatile float x[4] = {0};
// x array for holding recent inputs (newest input as index 0, delay of 1 at index 1, etc.
    static volatile float y[4] = {0};
    x[0] = sample;
// Calculate the output filtered signal based on a weighted sum of previous inputs/outputs
    y[0] = (b[0]*x[0]+b[1]*x[1]+b[2]*x[2]+b[3]*x[3])-(a[1]*y[1]+a[2]*y[2]+a[3]*y[3]);
    y[0] /= a[0];
// Shift the input signals by one timestep to prepare for the next call to this function
    x[3] = x[2];
    x[2] = x[1];
    x[1] = x[0];
// Shift the previously calculated output signals by one time step to prepare for the next call to this function
    y[3] = y[2];
    y[2] = y[1];
    y[1] = y[0];
    return y[0];
}

float boxcar(float sample)
{
    static const int boxcarWidth = 30; // Change this value to alter boxcar length
    static float recentSamples[boxcarWidth] = {0}; // hold onto recent samples
    static int readIndex = 0; // the index of the current reading
    static float total = 0; // the running total
    static float average = 0; // the average
// subtract the last reading:
    total = total - recentSamples[readIndex];
// add new sample to list (overwrite oldest sample)
    recentSamples[readIndex] = sample;
// add the reading to the total:
    total = total + recentSamples[readIndex];
// advance to the next position in the array:
    readIndex = readIndex + 1;
// if we're at the end of the array...
    if (readIndex >= boxcarWidth) {
// ...wrap around to the beginning:
        readIndex = 0;
    }
// calculate the average:
    average = total / boxcarWidth;
// send it to the computer as ASCII digits
    return average;
}
float complement(float x, float y , float ratio)
{
    return (ratio*x + (1 - ratio)*y);
}