Incorporate Filters code into NuEVI repo for smoother setup.

NuEVI/FilterOnePole.h

@@ -0,0 +1,89 @@
+// Copyright 2014 Jonathan Driscoll
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// FilterOnePole has been copied from https://github.com/JonHub/Filters
+
+
+#ifndef FilterOnePole_h
+#define FilterOnePole_h
+
+enum FILTER_TYPE {
+  HIGHPASS,
+  LOWPASS,
+  INTEGRATOR,
+  DIFFERENTIATOR
+};
+
+// the recursive filter class implements a recursive filter (low / pass / highpass
+// note that this must be updated in a loop, using the most recent acquired values and the time acquired
+//   Y = a0*X + a1*Xm1
+//              + b1*Ylast
+struct FilterOnePole {
+  FILTER_TYPE FT;
+  float TauUS;       // decay constant of the filter, in US
+  float TauSamps;    // tau, measued in samples (this changes, depending on how long between input()s
+
+  // filter values - these are public, but should not be set externally
+  float Y;       // most recent output value (gets computed on update)
+  float Ylast;   // prevous output value
+
+  float X;      // most recent input value
+
+  // elapsed times are kept in long, and will wrap every
+  // 35 mins, 47 seconds ... however, the wrap does not matter,
+  // because the delta will still be correct (always positive and small)
+  float ElapsedUS;   // time since last update
+  long LastUS;       // last time measured
+
+  FilterOnePole( FILTER_TYPE ft=LOWPASS, float fc=1.0, float initialValue=0 );
+
+  // sets or resets the parameters and state of the filter
+  void setFilter( FILTER_TYPE ft, float tauS, float initialValue );
+
+  void setFrequency( float newFrequency );
+
+  void setTau( float newTau );
+
+  float input( float inVal );
+
+  float output();
+
+  void print();
+
+  void test();
+
+  void setToNewValue( float newVal );  // resets the filter to a new value
+};
+
+// two pole filter, these are very useful
+struct FilterOnePoleCascade {
+
+  FilterOnePole Pole1;
+  FilterOnePole Pole2;
+
+  FilterOnePoleCascade( float riseTime=1.0, float initialValue=0 );  // rise time to step function, 10% to 90%
+
+  // rise time is 10% to 90%, for a step input
+  void setRiseTime( float riseTime );
+
+  void setToNewValue( float newVal );
+
+  float input( float inVal );
+
+  float output();
+
+  void test();
+};
+
+#endif