Portamento.h

/*
 * Portamento.h
 *
 * Copyright 2012 Tim Barrass.
 *
 * This file is part of Mozzi.
 *
 * Mozzi is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
 *
 */

#ifndef PORTAMENTO_H_
#define PORTAMENTO_H_

#include "mozzi_midi.h"
#include "mozzi_fixmath.h"
#include "Line.h"

/** A simple portamento (pitch slide from one note to the next) effect, useful for note-based applications.
*/
template <unsigned int CONTROL_UPDATE_RATE>
class
    Portamento {

public:

    /** Constructor.
     */
    Portamento():
            MICROS_PER_CONTROL_STEP(1000000/CONTROL_UPDATE_RATE)
    {
    }

    /** Set how long it will take to slide from note to note, in milliseconds.
    @param milliseconds
    */
    inline
    void setTime(unsigned int milliseconds){
        //control_steps_per_portamento = ((long)milliseconds*1000)/MICROS_PER_CONTROL_STEP; // more accurate but slower
        control_steps_per_portamento = convertMsecToControlSteps(milliseconds);
    }

    /** Call this at note-on, it initialises the portamento.
    @param note a midi note number, a whole number.
    */
    inline
    void start(uint8_t note) {
        target_freq = Q16n16_mtof(Q8n0_to_Q16n16(note));
        aPortamentoLine.set(target_freq, control_steps_per_portamento);
        countdown = control_steps_per_portamento;
        portamento_on=true;
    }

    /** Call this at note-on, it initialises the portamento.
    @param note a midi note number in Q16n16 fractional format.  This is useful for non-whole note or detuned values.
    */
    inline
    void start(Q16n16 note) {
        target_freq = Q16n16_mtof(note);
        aPortamentoLine.set(target_freq, control_steps_per_portamento);
        countdown = control_steps_per_portamento;
        portamento_on=true;
    }


    /** Use this in updateControl() to provide a frequency to the oscillator it's controlling. 
    For example: 
    myOscil.setFreq_Q16n16(myPortamento.next());
    @return a Q16n16 fractional frequency value, progressing smoothly between successive notes.
    */
    inline
    Q16n16 next() {
        if (portamento_on==true){
            if(--countdown < 0) {
                // stay level when portamento has finished
                aPortamentoLine.set(target_freq, target_freq, control_steps_per_portamento);
                portamento_on=false;
            }
        }
        return aPortamentoLine.next();
    }

    private:

    int countdown;
    int control_steps_per_portamento;
    Q16n16 target_freq;
    bool portamento_on;
    const unsigned int MICROS_PER_CONTROL_STEP;
    Line <Q16n16> aPortamentoLine;


    // copied from ADSR.h
    inline
    static const unsigned int convertMsecToControlSteps(unsigned int msec){
        return (uint16_t) (((uint32_t)msec*CONTROL_UPDATE_RATE)>>10); // approximate /1000 with shift
    }

};

/**
@example 05.Control_Filters/Teensy_USB_MIDI_portamento/Teensy_USB_MIDI_portamento.ino
This example demonstrates the Portamento class.
*/

#endif /* PORTAMENTO_H_ */