commit 84370bd932dc17dcd3b521c2ebebf07e1b5cf918 Author: Stuart Longland Date: Sat Apr 8 18:54:00 2017 +1000 ADSR-based synthesizer for microcontrollers Initial check-in. diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..2641cde --- /dev/null +++ b/.gitignore @@ -0,0 +1,5 @@ +.*.swp +*.swp +*.o +*.elf +*.hex diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..3912109 --- /dev/null +++ b/LICENSE @@ -0,0 +1,340 @@ + GNU GENERAL PUBLIC LICENSE + Version 2, June 1991 + + Copyright (C) 1989, 1991 Free Software Foundation, Inc. + 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The licenses for most software are designed to take away your +freedom to share and change it. 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If this is what you want to do, use the GNU Library General +Public License instead of this License. diff --git a/Makefile b/Makefile new file mode 100644 index 0000000..0a44866 --- /dev/null +++ b/Makefile @@ -0,0 +1,58 @@ +# Compiler definitions +CROSS_COMPILE ?= avr- +CC = $(CROSS_COMPILE)gcc +AR = $(CROSS_COMPILE)ar +OBJCOPY = $(CROSS_COMPILE)objcopy +OBJDUMP = $(CROSS_COMPILE)objdump +SIZE = $(CROSS_COMPILE)size +MCU ?= attiny85 +CFLAGS ?= -g -mmcu=$(MCU) -O3 -Werror -Woverflow +CPPFLAGS ?= -DF_CPU=$(FREQ) -D_POLY_CFG=\"poly_cfg.h\" +LDFLAGS ?= -mmcu=$(MCU) -O3 -Wl,--as-needed +PROG ?= avrdude +PROG_ARGS ?= -B 10 -c stk500v2 -P /dev/ttyACM0 +PROG_DEV ?= t85 + +BINDIR ?= bin +SRCDIR ?= . +OBJDIR ?= obj + +LFUSE=0xc1 +HFUSE=0xdf +EFUSE=0xff +FREQ=16000000 + +.PHONY: setfuse all clean + +-include local.mk + +all: bindir/synth.hex + +%.hex: %.elf + $(OBJCOPY) -j .text -j .data -O ihex $< $@ + +$(BINDIR)/synth.elf: $(OBJDIR)/main.o $(OBJDIR)/poly.a + @[ -d $(BINDIR) ] || mkdir $(BINDIR) + $(CC) -g -o $@ $(LDFLAGS) $^ + +$(OBJDIR)/poly.a: $(OBJDIR)/adsr.o $(OBJDIR)/waveform.o + $(AR) rcs $@ $^ + +$(OBJDIR)/%.o: $(SRCDIR)/%.c + @[ -d $(OBJDIR) ] || mkdir $(OBJDIR) + $(CC) -o $@ -c $(CPPFLAGS) $(CFLAGS) $< + +clean: + -rm -fr $(OBJDIR) $(BINDIR) + +%.ihex: %.elf + $(OBJCOPY) -j .text -j .data -O ihex $^ $@ + +%.pgm: %.ihex + $(PROG) $(PROG_ARGS) -p $(PROG_DEV) -U flash:w:$^:i + +setfuse: + $(PROG) $(PROG_ARGS) -p $(PROG_DEV) \ + -U lfuse:w:$(LFUSE):m \ + -U hfuse:w:$(HFUSE):m \ + -U efuse:w:$(EFUSE):m diff --git a/README.md b/README.md new file mode 100644 index 0000000..eebfd4b --- /dev/null +++ b/README.md @@ -0,0 +1,15 @@ +ADSR-based Polyphonic Synthesizer +================================= + +This project is intended to be a polyphonic synthesizer for use in +embedded microcontrollers. It features multi-voice synthesis for multiple +channels. + +The synthesis is inspired from the highly regarded MOS Technologies 6581 +"SID" chip, which supported up to 3 voices each producing either a +square wave, triangle wave or sawtooth wave output and hardware +attack/decay/sustain/release envelope generation. + +This tries to achieve the same thing in software. + +Code is presently a work-in-progress. diff --git a/adsr.c b/adsr.c new file mode 100644 index 0000000..2c2c30a --- /dev/null +++ b/adsr.c @@ -0,0 +1,227 @@ +/*! + * 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 + */ + +#include "adsr.h" +#include +#ifdef __AVR_ARCH__ +#include +#endif + +/* ADSR attack/decay adjustments */ +#define ADSR_EXP_AMP_FACTOR (6) +#define ADSR_EXP_SHIFT (-8) +#define ADSR_EXP_TIME_FACTOR (1) +#define ADSR_LIN_AMP_FACTOR (6) +#define ADSR_DECAY_OFFSET (16) + +/*! + * ADSR Attack amplitude exponential shift. + */ +static uint8_t adsr_attack_shift(uint8_t sample) { + return (sample + ADSR_EXP_SHIFT)/ADSR_EXP_TIME_FACTOR + - ADSR_EXP_AMP_FACTOR; +} + +/*! + * ADSR Release amplitude exponential shift. + */ +static uint8_t adsr_release_shift(uint8_t sample) { + return adsr_attack_shift(ADSR_DECAY_OFFSET - sample); +} + +/*! + * Reset the ADSR state ready for the next note + */ +void adsr_reset(struct adsr_env_gen_t* const adsr) { + adsr->next_event = 0; + adsr->state = ADSR_STATE_IDLE; +} + +/*! + * Compute the ADSR amplitude + */ +uint8_t adsr_next(struct adsr_env_gen_t* const adsr) { + if (adsr->next_event) { + /* Still waiting for next event */ + adsr->next_event--; + return adsr->amplitude; + } + + /* + * We use if statements here since we might want to jump + * between states. This lets us do that more easily. + */ + + if (adsr->state == ADSR_STATE_IDLE) { + /* Are registers set up? */ + if (!adsr->time_scale) + return 0; + if (!(adsr->delay_time || adsr->attack_time + || adsr->decay_time || adsr->release_time)) + return 0; + if (!(adsr->peak_amp || adsr->sustain_amp)) + return 0; + + /* All good */ + if (adsr->delay_time) + adsr->state = ADSR_STATE_DELAY_INIT; + else + adsr->state = ADSR_STATE_DELAY_EXPIRE; + } + + if (adsr->state == ADSR_STATE_DELAY_INIT) { + /* Setting up a delay */ + adsr->amplitude = 0; + adsr->next_event = adsr->time_scale + * adsr->delay_time; + adsr->state = ADSR_STATE_DELAY_EXPIRE; + /* Wait for delay */ + return adsr->amplitude; + } + + if (adsr->state == ADSR_STATE_DELAY_EXPIRE) { + /* Delay has expired */ + if (adsr->attack_time) + adsr->state = ADSR_STATE_ATTACK_INIT; + else + adsr->state = ADSR_STATE_ATTACK_EXPIRE; + } + + if (adsr->state == ADSR_STATE_ATTACK_INIT) { + /* Attack is divided into 16 segments */ + adsr->time_step = (uint16_t)((adsr->attack_time + * adsr->time_scale) >> 4); + adsr->counter = 16; + adsr->next_event = adsr->time_step; + adsr->state = ADSR_STATE_ATTACK; + } + + if (adsr->state == ADSR_STATE_ATTACK) { + if (adsr->counter) { + /* Change of amplitude */ + uint16_t lin_amp = (16-adsr->counter) + * adsr->peak_amp; + adsr->amplitude = lin_amp + >> ADSR_LIN_AMP_FACTOR; + adsr->amplitude += adsr->peak_amp >> + adsr_attack_shift(adsr->counter); + /* Go around again */ + adsr->counter--; + adsr->next_event = adsr->time_step; + return adsr->amplitude; + } else { + adsr->state = ADSR_STATE_ATTACK_EXPIRE; + } + } + + if (adsr->state == ADSR_STATE_ATTACK_EXPIRE) { + if (adsr->decay_time) + adsr->state = ADSR_STATE_DECAY_INIT; + else + adsr->state = ADSR_STATE_DECAY_EXPIRE; + } + + if (adsr->state == ADSR_STATE_DECAY_INIT) { + /* We should be at full amplitude */ + adsr->amplitude = adsr->peak_amp; + + adsr->time_step = (uint16_t)((adsr->decay_time + * adsr->time_scale) >> 4); + adsr->counter = 16; + adsr->next_event = adsr->time_step; + adsr->state = ADSR_STATE_DECAY; + } + + if (adsr->state == ADSR_STATE_DECAY) { + if (adsr->counter) { + /* Linear decrease in amplitude */ + uint16_t delta = adsr->peak_amp + - adsr->sustain_amp; + delta *= adsr->counter; + delta >>= 4; + + adsr->amplitude = adsr->sustain_amp + delta; + adsr->next_event = adsr->time_step; + adsr->counter--; + } else { + adsr->state = ADSR_STATE_DECAY_EXPIRE; + } + } + + if (adsr->state == ADSR_STATE_DECAY_EXPIRE) { + if (adsr->sustain_time) + adsr->state = ADSR_STATE_SUSTAIN_INIT; + else + adsr->state = ADSR_STATE_SUSTAIN_EXPIRE; + } + + if (adsr->state == ADSR_STATE_SUSTAIN_INIT) { + adsr->amplitude = adsr->sustain_amp; + adsr->next_event = adsr->time_scale + * adsr->sustain_time; + adsr->state = ADSR_STATE_SUSTAIN_EXPIRE; + /* Wait for delay */ + return adsr->amplitude; + } + + if (adsr->state == ADSR_STATE_SUSTAIN_EXPIRE) { + if (adsr->release_time) + adsr->state = ADSR_STATE_RELEASE_INIT; + else + adsr->state = ADSR_STATE_RELEASE_EXPIRE; + } + + if (adsr->state == ADSR_STATE_RELEASE_INIT) { + adsr->time_step = (uint16_t)((adsr->release_time + * adsr->time_scale) >> 4); + adsr->counter = 16; + adsr->next_event = adsr->time_step; + adsr->state = ADSR_STATE_RELEASE; + } + + if (adsr->state == ADSR_STATE_RELEASE) { + if (adsr->counter) { + /* Change of amplitude */ + uint16_t lin_amp = adsr->counter + * adsr->peak_amp; + adsr->amplitude = lin_amp + >> ADSR_LIN_AMP_FACTOR; + adsr->amplitude += adsr->peak_amp >> + adsr_release_shift(adsr->counter); + /* Go around again */ + adsr->counter--; + adsr->next_event = adsr->time_step; + } else { + adsr->state = ADSR_STATE_RELEASE_EXPIRE; + } + } + + if (adsr->state == ADSR_STATE_RELEASE_EXPIRE) { + /* Reset the state */ + adsr->state = ADSR_STATE_IDLE; + adsr->amplitude = 0; + } + + return adsr->amplitude; +} + +/* + * vim: set sw=8 ts=8 noet si tw=72 + */ diff --git a/adsr.h b/adsr.h new file mode 100644 index 0000000..0d9e06b --- /dev/null +++ b/adsr.h @@ -0,0 +1,85 @@ +/*! + * 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 + +/* 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) + +/*! + * ADSR Envelope Generator data. 20 bytes. + */ +struct adsr_env_gen_t { + /*! Time to next event, samples */ + 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_t delay_time; + /*! Attack period, time units */ + uint8_t attack_time; + /*! Decay period, time units */ + uint8_t decay_time; + /*! Sustain period, time units */ + 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 + */ +void adsr_reset(struct adsr_env_gen_t* const adsr); + +/*! + * Compute the ADSR amplitude + */ +uint8_t adsr_next(struct adsr_env_gen_t* const adsr); +#endif +/* + * vim: set sw=8 ts=8 noet si tw=72 + */ diff --git a/synth.h b/synth.h new file mode 100644 index 0000000..cf85ca1 --- /dev/null +++ b/synth.h @@ -0,0 +1,97 @@ +/*! + * Polyphonic synthesizer for microcontrollers. + * (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 _SYNTH_H +#define _SYNTH_H +#include "voice.h" + +/* + * _POLY_CFG_H is a definition that can be given when compiling poly.c + * and firmware code to define a header file that contains definitions for + * the Polyphonic synthesizer. + */ +#ifdef SYNTH_CFG +#include SYNTH_CFG +#endif + +#ifndef SYNTH_FREQ +/*! + * Sample rate for the synthesizer: this needs to be declared in the + * application. + */ +extern const uint16_t __attribute__((weak)) synth_freq; +#else +#define synth_freq SYNTH_FREQ +#endif + +/*! + * Polyphonic synthesizer structure + */ +struct poly_synth_t { + /*! Pointer to voices. There may be up to 16 voices referenced. */ + struct voice_ch_t* const voice; + /*! + * Bit-field enabling given voices. This allows selective turning + * on and off of given voice channels. If the corresponding bit is + * not a 1, then that channel is not computed. + * + * Note no bounds checking is done, if you have only defined 4 + * channels, then only set bits 0-3, don't set bits 4 onwards here. + */ + uintptr_t enable; + /*! + * Bit-field muting given voices. This allows for selective adding + * of voices to the overall output. If a field is 1, then that voice + * channel is not included. (Note, disabled channels are *also* + * not included.) + */ + uintptr_t mute; +}; + +/*! + * Compute the next synthesizer sample. + */ +static inline int8_t poly_synth_next(struct poly_synth_t* const synth) { + int16_t sample = 0; + uintptr_t mask = 1; + uint8_t idx = 0; + + while (mask) { + if (synth->enable & mask) { + /* Channel is enabled */ + int8_t ch_sample = voice_ch_next( + &(synth->voice[idx])); + if (!(synth->mute & mask)) + sample += ch_sample; + } + idx++; + mask <<= 1; + } + + /* Handle clipping */ + if (sample > INT8_MAX) + sample = INT8_MAX; + else if (sample < INT8_MIN) + sample = INT8_MIN; + return sample; +}; +#endif +/* + * vim: set sw=8 ts=8 noet si tw=72 + */ diff --git a/voice.h b/voice.h new file mode 100644 index 0000000..8a87366 --- /dev/null +++ b/voice.h @@ -0,0 +1,61 @@ +/*! + * Polyphonic synthesizer for microcontrollers. Voice generation. + * (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 + */ + +#include "waveform.h" +#include "adsr.h" + + +/*! + * Voice channel state. 30 bytes. + */ +struct voice_ch_t { + /*! + * ADSR Envelope generator state. + */ + struct adsr_env_gen_t adsr; + /*! + * Waveform generator state. + */ + struct voice_wf_gen_t wf; +}; + +/*! + * Compute the next voice channel sample. + */ +inline static int8_t voice_ch_next(struct voice_ch_t* const voice) { + uint8_t amplitude = adsr_next(&(voice->adsr)); + if (!amplitude) + return 0; + + int16_t value = voice_wf_next(&(voice->wf)); + value *= amplitude; + + /* Saturation handling */ + if (value < INT8_MIN) + return INT8_MIN; + else if (value > INT8_MAX) + return INT8_MAX; + else + return value; +} + +/* + * vim: set sw=8 ts=8 noet si tw=72 + */ diff --git a/waveform.c b/waveform.c new file mode 100644 index 0000000..717eb05 --- /dev/null +++ b/waveform.c @@ -0,0 +1,136 @@ +/*! + * Polyphonic synthesizer for microcontrollers. Voice waveform 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 + */ + +#include "waveform.h" +#include "synth.h" +#include + +/* Waveform generation modes */ +#define VOICE_MODE_DC (0) +#define VOICE_MODE_SQUARE (1) +#define VOICE_MODE_SAWTOOTH (2) +#define VOICE_MODE_TRIANGLE (3) +#define VOICE_MODE_NOISE (4) + +/* Amplitude scaling */ +#define VOICE_WF_AMP_SCALE (8) + +int8_t voice_wf_next(struct voice_wf_gen_t* const wf_gen) { + switch(wf_gen->mode) { + case VOICE_MODE_DC: + return wf_gen->amplitude; + case VOICE_MODE_NOISE: + wf_gen->sample = (rand() / + (RAND_MAX/512)) - 256; + wf_gen->sample *= wf_gen->amplitude; + break; + case VOICE_MODE_SQUARE: + if (!wf_gen->period_remain) { + /* Swap value */ + wf_gen->sample = -wf_gen->sample; + wf_gen->period_remain = wf_gen->period; + } else { + wf_gen->period_remain--; + } + break; + case VOICE_MODE_SAWTOOTH: + if (!wf_gen->period_remain) { + /* Back to -amplitude */ + wf_gen->sample = -wf_gen->amplitude + << VOICE_WF_AMP_SCALE; + wf_gen->period_remain = wf_gen->period; + } else { + wf_gen->sample += wf_gen->step; + wf_gen->period_remain--; + } + break; + case VOICE_MODE_TRIANGLE: + if (!wf_gen->period_remain) { + /* Switch direction */ + if (wf_gen->step > 0) + wf_gen->sample = -wf_gen->amplitude; + else + wf_gen->sample = wf_gen->amplitude; + wf_gen->step = -wf_gen->step; + wf_gen->period_remain = wf_gen->period; + } else { + wf_gen->sample += wf_gen->step; + wf_gen->period_remain--; + } + break; + } + + return wf_gen->sample >> VOICE_WF_AMP_SCALE; +} + +/* Compute frequency period (sawtooth wave) */ +static uint8_t voice_wf_calc_sawtooth_period(uint16_t freq) { + return (synth_freq / freq); +} + +/* Compute frequency period (square/triangle wave) */ +static uint8_t voice_wf_calc_square_period(uint16_t freq) { + return voice_wf_calc_sawtooth_period(freq) >> 1; +} + + +void voice_wf_set_dc(struct voice_wf_gen_t* const wf_gen, + uint8_t amplitude) { + wf_gen->mode = VOICE_MODE_DC; + wf_gen->amplitude = amplitude; +} + +void voice_wf_set_square(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude) { + wf_gen->mode = VOICE_MODE_SQUARE; + wf_gen->amplitude = amplitude << VOICE_WF_AMP_SCALE; + wf_gen->period = voice_wf_calc_square_period(freq); + wf_gen->period_remain = wf_gen->period; + wf_gen->sample = wf_gen->amplitude; +} + +void voice_wf_set_sawtooth(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude) { + wf_gen->mode = VOICE_MODE_SAWTOOTH; + wf_gen->sample = wf_gen->amplitude << VOICE_WF_AMP_SCALE; + wf_gen->period = voice_wf_calc_sawtooth_period(freq); + wf_gen->period_remain = wf_gen->period; + wf_gen->amplitude = -wf_gen->sample; + wf_gen->step = ((int32_t)(wf_gen->amplitude << 1)) / wf_gen->period; +} + +void voice_wf_set_triangle(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude) { + wf_gen->mode = VOICE_MODE_TRIANGLE; + wf_gen->sample = wf_gen->amplitude << VOICE_WF_AMP_SCALE; + wf_gen->period = voice_wf_calc_square_period(freq); + wf_gen->period_remain = wf_gen->period; + wf_gen->amplitude = -wf_gen->sample; + wf_gen->step = ((int32_t)(wf_gen->amplitude << 1)) / wf_gen->period; +} + +void voice_wf_set_noise(struct voice_wf_gen_t* const wf_gen, + uint8_t amplitude) { + wf_gen->mode = VOICE_MODE_SQUARE; + wf_gen->amplitude = amplitude; +} +/* + * vim: set sw=8 ts=8 noet si tw=72 + */ diff --git a/waveform.h b/waveform.h new file mode 100644 index 0000000..3a13c47 --- /dev/null +++ b/waveform.h @@ -0,0 +1,83 @@ +/*! + * Polyphonic synthesizer for microcontrollers. Voice waveform 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 _WAVEFORM_H +#define _WAVEFORM_H +#include + +/*! + * Waveform generator state. 10 bytes. + */ +struct voice_wf_gen_t { + /*! Waveform output sample in fixed-point */ + int16_t sample; + /*! Amplitude sample in fixed point */ + int16_t amplitude; + /*! Samples to next waveform period */ + uint16_t period_remain; + /*! + * Period duration in samples. + * (Half period for SQUARE and TRIANGLE) + */ + uint16_t period; + /*! Amplitude step for TRIANGLE and SAWTOOTH */ + int8_t step; + /*! Waveform generation mode */ + uint8_t mode; +}; + +/*! + * Configure the generator for a DC offset synthesis. + */ +void voice_wf_set_dc(struct voice_wf_gen_t* const wf_gen, + uint8_t amplitude); + +/*! + * Configure the generator for square wave synthesis. + */ +void voice_wf_set_square(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude); + +/*! + * Configure the generator for sawtooth wave synthesis. + */ +void voice_wf_set_sawtooth(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude); + +/*! + * Configure the generator for sawtooth wave synthesis. + */ +void voice_wf_set_triangle(struct voice_wf_gen_t* const wf_gen, + uint16_t freq, uint8_t amplitude); + +/*! + * Configure the generator for pseudorandom noise synthesis. + */ +void voice_wf_set_noise(struct voice_wf_gen_t* const wf_gen, + uint8_t amplitude); + +/*! + * Retrieve the next sample from the generator. + */ +int8_t voice_wf_next(struct voice_wf_gen_t* const wf_gen); + +#endif +/* + * vim: set sw=8 ts=8 noet si tw=72 + */