Diff: filter.cpp

Revision:

1:3258d62af038

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/filter.cpp	Wed Aug 01 22:39:10 2018 +0000
@@ -0,0 +1,52 @@
+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);
+}
\ No newline at end of file