PID.h

/*
 * 2011 Eberhard Rensch, Pleasant Software
 *
 * Based on parts of the Makerbot firmware
 * Copyright 2010 by Adam Mayer	 <adam@makerbot.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 * This simplified PID controller was written with reference to:
 * * The Heater.h implementation (lookup credits)
 * * Brett Beauregard's Arduino PID implementation
 *  Created on: Feb 19, 2010
 *      Author: phooky
 */

#ifndef PID_HH_
#define PID_HH_

#include <stdint.h>

#define DELTA_SAMPLES 4

/// This simplified PID controller makes several assumptions:
/// * The output range is limited to 0-255.
class PID {
private:
    // Data for approximating d (smoothing to handle discrete nature of sampling).
    // See PID.cc for a description of why we do this.
    int16_t delta_history[DELTA_SAMPLES];
    float delta_summation;
    uint8_t delta_idx;
    int prev_error; // previous input for calculating next delta
    int error_acc;  // accumulated error, for calculating integral

    int sp; // set point


public:
    PID() { reset(); }

    void setTarget(const int target) { sp = target; }
    const int getTarget() const { return sp; }

    /// Reset the PID to board-on values
    void reset();
    /// PV is the process value; that is, the measured value
    /// Returns the new value of the manipulated value; that is, the output
    int calculate(int pv);
};

#endif /* PID_HH_ */