stuartl/atinysynth
1
0
Fork 0
mirror of https://github.com/sjlongland/atinysynth.git synced 2025-09-14 02:23:15 +10:00
Code Issues Releases Wiki Activity

ADSR-based synthesizer for microcontrollers

Browse Source 
Initial check-in.
This commit is contained in:
Stuart Longland 2017-04-08 18:54:00 +10:00
commit 84370bd932
Signed by: stuartl
GPG Key ID: F954BBBB7948D546
10 changed files with 1107 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
.gitignore vendored Normal file
View File

@ -0,0 +1,5 @@
.*.swp
*.swp
*.o
*.elf
*.hex

340
LICENSE Normal file
View File

@ -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. By contrast, the GNU General Public
License is intended to guarantee your freedom to share and change free
software--to make sure the software is free for all its users. This
General Public License applies to most of the Free Software
Foundation's software and to any other program whose authors commit to
using it. (Some other Free Software Foundation software is covered by
the GNU Library General Public License instead.) You can apply it to
your programs, too.
When we speak of free software, we are referring to freedom, not
price. Our General Public Licenses are designed to make sure that you
have the freedom to distribute copies of free software (and charge for
this service if you wish), that you receive source code or can get it
if you want it, that you can change the software or use pieces of it
in new free programs; and that you know you can do these things.
To protect your rights, we need to make restrictions that forbid
anyone to deny you these rights or to ask you to surrender the rights.
These restrictions translate to certain responsibilities for you if you
distribute copies of the software, or if you modify it.
For example, if you distribute copies of such a program, whether
gratis or for a fee, you must give the recipients all the rights that
you have. You must make sure that they, too, receive or can get the
source code. And you must show them these terms so they know their
rights.
We protect your rights with two steps: (1) copyright the software, and
(2) offer you this license which gives you legal permission to copy,
distribute and/or modify the software.
Also, for each author's protection and ours, we want to make certain
that everyone understands that there is no warranty for this free
software. If the software is modified by someone else and passed on, we
want its recipients to know that what they have is not the original, so
that any problems introduced by others will not reflect on the original
authors' reputations.
Finally, any free program is threatened constantly by software
patents. We wish to avoid the danger that redistributors of a free
program will individually obtain patent licenses, in effect making the
program proprietary. To prevent this, we have made it clear that any
patent must be licensed for everyone's free use or not licensed at all.
The precise terms and conditions for copying, distribution and
modification follow.
GNU GENERAL PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License applies to any program or other work which contains
a notice placed by the copyright holder saying it may be distributed
under the terms of this General Public License. The "Program", below,
refers to any such program or work, and a "work based on the Program"
means either the Program or any derivative work under copyright law:
that is to say, a work containing the Program or a portion of it,
either verbatim or with modifications and/or translated into another
language. (Hereinafter, translation is included without limitation in
the term "modification".) Each licensee is addressed as "you".
Activities other than copying, distribution and modification are not
covered by this License; they are outside its scope. The act of
running the Program is not restricted, and the output from the Program
is covered only if its contents constitute a work based on the
Program (independent of having been made by running the Program).
Whether that is true depends on what the Program does.
1. You may copy and distribute verbatim copies of the Program's
source code as you receive it, in any medium, provided that you
conspicuously and appropriately publish on each copy an appropriate
copyright notice and disclaimer of warranty; keep intact all the
notices that refer to this License and to the absence of any warranty;
and give any other recipients of the Program a copy of this License
along with the Program.
You may charge a fee for the physical act of transferring a copy, and
you may at your option offer warranty protection in exchange for a fee.
2. You may modify your copy or copies of the Program or any portion
of it, thus forming a work based on the Program, and copy and
distribute such modifications or work under the terms of Section 1
above, provided that you also meet all of these conditions:
a) You must cause the modified files to carry prominent notices
stating that you changed the files and the date of any change.
b) You must cause any work that you distribute or publish, that in
whole or in part contains or is derived from the Program or any
part thereof, to be licensed as a whole at no charge to all third
parties under the terms of this License.
c) If the modified program normally reads commands interactively
when run, you must cause it, when started running for such
interactive use in the most ordinary way, to print or display an
announcement including an appropriate copyright notice and a
notice that there is no warranty (or else, saying that you provide
a warranty) and that users may redistribute the program under
these conditions, and telling the user how to view a copy of this
License. (Exception: if the Program itself is interactive but
does not normally print such an announcement, your work based on
the Program is not required to print an announcement.)
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the Program,
and can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to those
sections when you distribute them as separate works. But when you
distribute the same sections as part of a whole which is a work based
on the Program, the distribution of the whole must be on the terms of
this License, whose permissions for other licensees extend to the
entire whole, and thus to each and every part regardless of who wrote it.
Thus, it is not the intent of this section to claim rights or contest
your rights to work written entirely by you; rather, the intent is to
exercise the right to control the distribution of derivative or
collective works based on the Program.
In addition, mere aggregation of another work not based on the Program
with the Program (or with a work based on the Program) on a volume of
a storage or distribution medium does not bring the other work under
the scope of this License.
3. You may copy and distribute the Program (or a work based on it,
under Section 2) in object code or executable form under the terms of
Sections 1 and 2 above provided that you also do one of the following:
a) Accompany it with the complete corresponding machine-readable
source code, which must be distributed under the terms of Sections
1 and 2 above on a medium customarily used for software interchange; or,
b) Accompany it with a written offer, valid for at least three
years, to give any third party, for a charge no more than your
cost of physically performing source distribution, a complete
machine-readable copy of the corresponding source code, to be
distributed under the terms of Sections 1 and 2 above on a medium
customarily used for software interchange; or,
c) Accompany it with the information you received as to the offer
to distribute corresponding source code. (This alternative is
allowed only for noncommercial distribution and only if you
received the program in object code or executable form with such
an offer, in accord with Subsection b above.)
The source code for a work means the preferred form of the work for
making modifications to it. For an executable work, complete source
code means all the source code for all modules it contains, plus any
associated interface definition files, plus the scripts used to
control compilation and installation of the executable. However, as a
special exception, the source code distributed need not include
anything that is normally distributed (in either source or binary
form) with the major components (compiler, kernel, and so on) of the
operating system on which the executable runs, unless that component
itself accompanies the executable.
If distribution of executable or object code is made by offering
access to copy from a designated place, then offering equivalent
access to copy the source code from the same place counts as
distribution of the source code, even though third parties are not
compelled to copy the source along with the object code.
4. You may not copy, modify, sublicense, or distribute the Program
except as expressly provided under this License. Any attempt
otherwise to copy, modify, sublicense or distribute the Program is
void, and will automatically terminate your rights under this License.
However, parties who have received copies, or rights, from you under
this License will not have their licenses terminated so long as such
parties remain in full compliance.
5. You are not required to accept this License, since you have not
signed it. However, nothing else grants you permission to modify or
distribute the Program or its derivative works. These actions are
prohibited by law if you do not accept this License. Therefore, by
modifying or distributing the Program (or any work based on the
Program), you indicate your acceptance of this License to do so, and
all its terms and conditions for copying, distributing or modifying
the Program or works based on it.
6. Each time you redistribute the Program (or any work based on the
Program), the recipient automatically receives a license from the
original licensor to copy, distribute or modify the Program subject to
these terms and conditions. You may not impose any further
restrictions on the recipients' exercise of the rights granted herein.
You are not responsible for enforcing compliance by third parties to
this License.
7. If, as a consequence of a court judgment or allegation of patent
infringement or for any other reason (not limited to patent issues),
conditions are imposed on you (whether by court order, agreement or
otherwise) that contradict the conditions of this License, they do not
excuse you from the conditions of this License. If you cannot
distribute so as to satisfy simultaneously your obligations under this
License and any other pertinent obligations, then as a consequence you
may not distribute the Program at all. For example, if a patent
license would not permit royalty-free redistribution of the Program by
all those who receive copies directly or indirectly through you, then
the only way you could satisfy both it and this License would be to
refrain entirely from distribution of the Program.
If any portion of this section is held invalid or unenforceable under
any particular circumstance, the balance of the section is intended to
apply and the section as a whole is intended to apply in other
circumstances.
It is not the purpose of this section to induce you to infringe any
patents or other property right claims or to contest validity of any
such claims; this section has the sole purpose of protecting the
integrity of the free software distribution system, which is
implemented by public license practices. Many people have made
generous contributions to the wide range of software distributed
through that system in reliance on consistent application of that
system; it is up to the author/donor to decide if he or she is willing
to distribute software through any other system and a licensee cannot
impose that choice.
This section is intended to make thoroughly clear what is believed to
be a consequence of the rest of this License.
8. If the distribution and/or use of the Program is restricted in
certain countries either by patents or by copyrighted interfaces, the
original copyright holder who places the Program under this License
may add an explicit geographical distribution limitation excluding
those countries, so that distribution is permitted only in or among
countries not thus excluded. In such case, this License incorporates
the limitation as if written in the body of this License.
9. The Free Software Foundation may publish revised and/or new versions
of the General Public License from time to time. Such new versions will
be similar in spirit to the present version, but may differ in detail to
address new problems or concerns.
Each version is given a distinguishing version number. If the Program
specifies a version number of this License which applies to it and "any
later version", you have the option of following the terms and conditions
either of that version or of any later version published by the Free
Software Foundation. If the Program does not specify a version number of
this License, you may choose any version ever published by the Free Software
Foundation.
10. If you wish to incorporate parts of the Program into other free
programs whose distribution conditions are different, write to the author
to ask for permission. For software which is copyrighted by the Free
Software Foundation, write to the Free Software Foundation; we sometimes
make exceptions for this. Our decision will be guided by the two goals
of preserving the free status of all derivatives of our free software and
of promoting the sharing and reuse of software generally.
NO WARRANTY
11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
REPAIR OR CORRECTION.
12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Programs
If you develop a new program, and you want it to be of the greatest
possible use to the public, the best way to achieve this is to make it
free software which everyone can redistribute and change under these terms.
To do so, attach the following notices to the program. It is safest
to attach them to the start of each source file to most effectively
convey the exclusion of warranty; and each file should have at least
the "copyright" line and a pointer to where the full notice is found.
<one line to give the program's name and a brief idea of what it does.>
Copyright (C) <year> <name of author>
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
Also add information on how to contact you by electronic and paper mail.
If the program is interactive, make it output a short notice like this
when it starts in an interactive mode:
Gnomovision version 69, Copyright (C) year name of author
Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
The hypothetical commands `show w' and `show c' should show the appropriate
parts of the General Public License. Of course, the commands you use may
be called something other than `show w' and `show c'; they could even be
mouse-clicks or menu items--whatever suits your program.
You should also get your employer (if you work as a programmer) or your
school, if any, to sign a "copyright disclaimer" for the program, if
necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the program
`Gnomovision' (which makes passes at compilers) written by James Hacker.
<signature of Ty Coon>, 1 April 1989
Ty Coon, President of Vice
This General Public License does not permit incorporating your program into
proprietary programs. If your program is a subroutine library, you may
consider it more useful to permit linking proprietary applications with the
library. If this is what you want to do, use the GNU Library General
Public License instead of this License.

58
Makefile Normal file
View File

@ -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

15
README.md Normal file
View File

@ -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.

227
adsr.c Normal file
View File

@ -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 <stdlib.h>
#ifdef __AVR_ARCH__
#include <avr/pgmspace.h>
#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
*/

85
adsr.h Normal file
View File

@ -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 <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)
/*!
* 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
*/

97
synth.h Normal file
View File

@ -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
*/

61
voice.h Normal file
View File

@ -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
*/

136
waveform.c Normal file
View File

@ -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 <stdlib.h>
/* 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
*/

83
waveform.h Normal file
View File

@ -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 <stdint.h>
/*!
* 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
*/