DaisySP_TeensyDaisySP_Teensy/DaisySP/Control/adsr.cpp

#include "adsr.h"
#include <math.h>

using namespace daisysp;

float Adsr::Tau2Pole(float tau)
{
    return expf(-1.0f / (tau * sample_rate_));
}

float Adsr::AdsrFilter()
{
    y_ = b_ * x_ + a_ * y_;
    return y_;
}


void Adsr::Init(float sample_rate)
{
    seg_time_[ADSR_SEG_ATTACK]  = 0.1f;
    seg_time_[ADSR_SEG_DECAY]   = 0.1f;
    sus_                        = 0.7f;
    seg_time_[ADSR_SEG_RELEASE] = 0.1f;
    //timer_ = 0;
    a_           = 0.0f;
    b_           = 0.0f;
    x_           = 0.0f;
    y_           = 0.0f;
    prev_        = 0.0f;
    atk_time_    = seg_time_[ADSR_SEG_ATTACK] * sample_rate;
    sample_rate_ = sample_rate;
}

float Adsr::Process(bool gate)
{
    float pole, out;
    out = 0.0f;

    if(gate && mode_ != ADSR_SEG_DECAY)
    {
        mode_ = ADSR_SEG_ATTACK;
        //timer_ = 0;
        pole      = Tau2Pole(seg_time_[ADSR_SEG_ATTACK] * 0.6f);
        atk_time_ = seg_time_[ADSR_SEG_ATTACK] * sample_rate_;
        a_        = pole;
        b_        = 1.0f - pole;
    }
    else if(!gate && mode_ != ADSR_SEG_IDLE)
    {
        mode_ = ADSR_SEG_RELEASE;
        pole  = Tau2Pole(seg_time_[ADSR_SEG_RELEASE]);
        a_    = pole;
        b_    = 1.0f - pole;
    }

    x_    = (int)gate;
    prev_ = (int)gate;

    switch(mode_)
    {
        case ADSR_SEG_IDLE: out = 0.0f; break;
        case ADSR_SEG_ATTACK:
            out = AdsrFilter();

            if(out > .99f)
            {
                mode_ = ADSR_SEG_DECAY;
                pole  = Tau2Pole(seg_time_[ADSR_SEG_DECAY]);
                a_    = pole;
                b_    = 1.0f - pole;
            }
            break;
        case ADSR_SEG_DECAY:
        case ADSR_SEG_RELEASE:
            x_ *= sus_;
            out = AdsrFilter();
            if(out <= 0.01f)
                mode_ = ADSR_SEG_IDLE;
        default: break;
    }
    return out;
}