1 // Copyright 2019 Emilie Gillet.
2 //
3 // Author: Emilie Gillet (emilie.o.gillet@gmail.com)
4 //
5 // Permission is hereby granted, free of charge, to any person obtaining a copy
6 // of this software and associated documentation files (the "Software"), to deal
7 // in the Software without restriction, including without limitation the rights
8 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
9 // copies of the Software, and to permit persons to whom the Software is
10 // furnished to do so, subject to the following conditions:
11 //
12 // The above copyright notice and this permission notice shall be included in
13 // all copies or substantial portions of the Software.
14 //
15 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
21 // THE SOFTWARE.
22 //
23 // See http://creativecommons.org/licenses/MIT/ for more information.
24 //
25 // -----------------------------------------------------------------------------
26 //
27 // Threshold type filter that filters out slow jumps of a value.
28 
29 #ifndef STMLIB_DSP_HYSTERESIS_FILTER_H_
30 #define STMLIB_DSP_HYSTERESIS_FILTER_H_
31 
32 #include "stmlib/stmlib.h"
33 
34 namespace stmlib {
35 
36 class HysteresisFilter {
37  public:
HysteresisFilter()38   HysteresisFilter() { }
~HysteresisFilter()39   ~HysteresisFilter() { }
40 
Init(float threshold)41   void Init(float threshold) {
42     value_ = 0.0f;
43     threshold_ = threshold;
44   }
45 
Process(float value)46   inline float Process(float value) {
47     return Process(value, threshold_);
48   }
49 
Process(float value,float threshold)50   inline float Process(float value, float threshold) {
51     if (threshold == 0.0f) {
52       value_ = value;
53     } else {
54       float error = value - value_;
55       if (error > threshold) {
56         value_ = value - threshold;
57       } else if (error < -threshold) {
58         value_ = value + threshold;
59       }
60     }
61     return value_;
62   }
63 
value()64   inline float value() const { return value_; }
65 
66  private:
67   float value_;
68   float threshold_;
69 
70   DISALLOW_COPY_AND_ASSIGN(HysteresisFilter);
71 };
72 
73 }  // namespace stmlib
74 
75 #endif  // STMLIB_DSP_HYSTERESIS_FILTER_H_
76