mirror of
https://github.com/sjlongland/atinysynth.git
synced 2025-09-13 10:03:15 +10:00
Stuart Longland
7039dd1307
Add helper functions that report back whether the ADSR generator is in a given state. Namely, if it is "waiting" for a trigger, or it is idle.
165 lines
4.3 KiB
C
165 lines
4.3 KiB
C
/*!
|
|
* Polyphonic synthesizer for microcontrollers. ADSR Envelope generator.
|
|
* (C) 2017 Stuart Longland
|
|
*
|
|
* 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 2 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, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston,
|
|
* MA 02110-1301 USA
|
|
*/
|
|
#ifndef _ADSR_H
|
|
#define _ADSR_H
|
|
|
|
#include "debug.h"
|
|
#include <stdint.h>
|
|
|
|
/* ADSR states */
|
|
#define ADSR_STATE_IDLE (0x00)
|
|
#define ADSR_STATE_DELAY_INIT (0x10)
|
|
#define ADSR_STATE_DELAY_EXPIRE (0x1f)
|
|
#define ADSR_STATE_ATTACK_INIT (0x20)
|
|
#define ADSR_STATE_ATTACK (0x21)
|
|
#define ADSR_STATE_ATTACK_EXPIRE (0x2f)
|
|
#define ADSR_STATE_DECAY_INIT (0x30)
|
|
#define ADSR_STATE_DECAY (0x31)
|
|
#define ADSR_STATE_DECAY_EXPIRE (0x3f)
|
|
#define ADSR_STATE_SUSTAIN_INIT (0x40)
|
|
#define ADSR_STATE_SUSTAIN_EXPIRE (0x4f)
|
|
#define ADSR_STATE_RELEASE_INIT (0x50)
|
|
#define ADSR_STATE_RELEASE (0x51)
|
|
#define ADSR_STATE_RELEASE_EXPIRE (0x5f)
|
|
#define ADSR_STATE_DONE (0xff)
|
|
|
|
/*!
|
|
* Hold this state until `adsr_continue` is called. Valid for
|
|
* `delay_time` and `sustain_time` only.
|
|
*/
|
|
#define ADSR_INFINITE UINT8_MAX
|
|
|
|
/*!
|
|
* ADSR Envelope Generator data. 20 bytes.
|
|
*/
|
|
struct adsr_env_gen_t {
|
|
/*! Time to next event, samples. UINT32_MAX = infinite */
|
|
uint32_t next_event;
|
|
/*! Time step, samples */
|
|
uint16_t time_step;
|
|
/*! Time scale, samples per unit */
|
|
uint32_t time_scale;
|
|
/*! Delay period, time units. UINT8_MAX = infinite */
|
|
uint8_t delay_time;
|
|
/*! Attack period, time units */
|
|
uint8_t attack_time;
|
|
/*! Decay period, time units */
|
|
uint8_t decay_time;
|
|
/*! Sustain period, time units. UINT8_MAX = infinite */
|
|
uint8_t sustain_time;
|
|
/*! Release period, time units */
|
|
uint8_t release_time;
|
|
/*! Attack peak amplitude */
|
|
uint8_t peak_amp;
|
|
/*! Sustain amplitude */
|
|
uint8_t sustain_amp;
|
|
/*! Present amplitude */
|
|
uint8_t amplitude;
|
|
/*! ADSR state */
|
|
uint8_t state;
|
|
/*! ADSR counter */
|
|
uint8_t counter;
|
|
};
|
|
|
|
/*!
|
|
* Reset the ADSR state ready for the next note.
|
|
*/
|
|
static inline void adsr_reset(struct adsr_env_gen_t* const adsr) {
|
|
adsr->next_event = 0;
|
|
adsr->state = ADSR_STATE_IDLE;
|
|
_DPRINTF("adsr=%p INIT time_scale=%d "
|
|
"delay_time=%d "
|
|
"attack_time=%d "
|
|
"decay_time=%d "
|
|
"sustain_time=%d "
|
|
"release_time=%d "
|
|
"peak_amp=%d "
|
|
"sustain_amp=%d\n",
|
|
adsr, adsr->time_scale,
|
|
adsr->delay_time,
|
|
adsr->attack_time,
|
|
adsr->decay_time,
|
|
adsr->sustain_time,
|
|
adsr->release_time,
|
|
adsr->peak_amp,
|
|
adsr->sustain_amp);
|
|
}
|
|
|
|
/*!
|
|
* Configure the ADSR.
|
|
*/
|
|
static inline void adsr_config(struct adsr_env_gen_t* const adsr,
|
|
uint32_t time_scale, uint8_t delay_time,
|
|
uint8_t attack_time, uint8_t decay_time,
|
|
uint8_t sustain_time, uint8_t release_time,
|
|
uint8_t peak_amp, uint8_t sustain_amp) {
|
|
|
|
adsr->time_scale = time_scale;
|
|
adsr->delay_time = delay_time;
|
|
adsr->attack_time = attack_time;
|
|
adsr->decay_time = decay_time;
|
|
adsr->sustain_time = sustain_time;
|
|
adsr->release_time = release_time;
|
|
adsr->peak_amp = peak_amp;
|
|
adsr->sustain_amp = sustain_amp;
|
|
|
|
adsr_reset(adsr);
|
|
}
|
|
|
|
/*!
|
|
* Compute the ADSR amplitude
|
|
*/
|
|
uint8_t adsr_next(struct adsr_env_gen_t* const adsr);
|
|
|
|
/*!
|
|
* Test to see if the ADSR is done.
|
|
*/
|
|
static inline uint8_t adsr_is_done(struct adsr_env_gen_t* const adsr) {
|
|
return (adsr->state == ADSR_STATE_DONE);
|
|
}
|
|
|
|
/*!
|
|
* Test to see if the ADSR is awaiting a trigger.
|
|
*/
|
|
static inline uint8_t adsr_is_waiting(struct adsr_env_gen_t* const adsr) {
|
|
return ((adsr->next_event == UINT32_MAX)
|
|
&& ((adsr->state == ADSR_STATE_DELAY_EXPIRE)
|
|
|| (adsr->state == ADSR_STATE_SUSTAIN_EXPIRE)));
|
|
}
|
|
|
|
/*!
|
|
* Test to see if the ADSR is idle.
|
|
*/
|
|
static inline uint8_t adsr_is_idle(struct adsr_env_gen_t* const adsr) {
|
|
return (adsr->state == ADSR_STATE_IDLE);
|
|
}
|
|
|
|
/*!
|
|
* Tell the ADSR to move onto the next state.
|
|
*/
|
|
static inline void adsr_continue(struct adsr_env_gen_t* const adsr) {
|
|
adsr->next_event = 0;
|
|
}
|
|
|
|
#endif
|
|
/*
|
|
* vim: set sw=8 ts=8 noet si tw=72
|
|
*/
|