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