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/*
* Copyright 2009 Phil Burk, Mobileer Inc
*
* 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.
*/
package com.jsyn.unitgen;
import com.jsyn.ports.UnitInputPort;
import com.jsyn.ports.UnitOutputPort;
/**
* SchmidtTrigger unit.
* <P>
* Output logic level value with hysteresis. Transition high when input exceeds setLevel. Only go
* low when input is below resetLevel. This can be used to reject low level noise on the input
* signal. The default values for setLevel and resetLevel are both 0.0. Setting setLevel to 0.1 and
* resetLevel to -0.1 will give some hysteresis. The outputPulse is a single sample wide pulse set
* when the output transitions from low to high.
*
* <PRE>
* if (output == 0.0)
* output = (input > setLevel) ? 1.0 : 0.0;
* else if (output > 0.0)
* output = (input <= resetLevel) ? 0.0 : 1.0;
* else
* output = previous_output;
* </PRE>
*
* @author Phil Burk (C) 2009 Mobileer Inc
* @see Compare
*/
public class SchmidtTrigger extends UnitFilter {
public UnitInputPort setLevel;
public UnitInputPort resetLevel;
public UnitOutputPort outputPulse;
/* Define Unit Ports used by connect() and set(). */
public SchmidtTrigger() {
addPort(setLevel = new UnitInputPort("SetLevel"));
addPort(resetLevel = new UnitInputPort("ResetLevel"));
addPort(input = new UnitInputPort("Input"));
addPort(outputPulse = new UnitOutputPort("OutputPulse"));
}
@Override
public void generate(int start, int limit) {
double[] inPtr = input.getValues();
double[] pulsePtr = outputPulse.getValues();
double[] outPtr = output.getValues();
double[] setPtr = setLevel.getValues();
double[] resetPtr = resetLevel.getValues();
double outputValue = outPtr[0];
boolean state = (outputValue > UnitGenerator.FALSE);
for (int i = start; i < limit; i++) {
pulsePtr[i] = UnitGenerator.FALSE;
if (state) {
if (inPtr[i] <= resetPtr[i]) {
state = false;
outputValue = UnitGenerator.FALSE;
}
} else {
if (inPtr[i] > setPtr[i]) {
state = true;
outputValue = UnitGenerator.TRUE;
pulsePtr[i] = UnitGenerator.TRUE; /* Single impulse. */
}
}
outPtr[i] = outputValue;
}
}
}
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