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Diffstat (limited to 'services/sensorservice/legacy/SecondOrderLowPassFilter.h')
-rw-r--r-- | services/sensorservice/legacy/SecondOrderLowPassFilter.h | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/services/sensorservice/legacy/SecondOrderLowPassFilter.h b/services/sensorservice/legacy/SecondOrderLowPassFilter.h new file mode 100644 index 0000000..85698ca --- /dev/null +++ b/services/sensorservice/legacy/SecondOrderLowPassFilter.h @@ -0,0 +1,73 @@ +/* + * Copyright (C) 2010 The Android Open Source Project + * + * 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. + */ + +#ifndef ANDROID_SECOND_ORDER_LOW_PASS_FILTER_H +#define ANDROID_SECOND_ORDER_LOW_PASS_FILTER_H + +#include <stdint.h> +#include <sys/types.h> + +// --------------------------------------------------------------------------- + +namespace android { +// --------------------------------------------------------------------------- + +class BiquadFilter; + +/* + * State of a 2nd order low-pass IIR filter + */ +class SecondOrderLowPassFilter { + friend class BiquadFilter; + float iQ, fc; + float K, iD; + float a0, a1; + float b1, b2; +public: + SecondOrderLowPassFilter(float Q, float fc); + void setSamplingPeriod(float dT); +}; + +/* + * Implements a Biquad IIR filter + */ +class BiquadFilter { + float x1, x2; + float y1, y2; + const SecondOrderLowPassFilter& s; +public: + BiquadFilter(const SecondOrderLowPassFilter& s); + float init(float in); + float operator()(float in); +}; + +/* + * Two cascaded biquad IIR filters + * (4-poles IIR) + */ +class CascadedBiquadFilter { + BiquadFilter mA; + BiquadFilter mB; +public: + CascadedBiquadFilter(const SecondOrderLowPassFilter& s); + float init(float in); + float operator()(float in); +}; + +// --------------------------------------------------------------------------- +}; // namespace android + +#endif // ANDROID_SECOND_ORDER_LOW_PASS_FILTER_H |