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// midi.c - main program for Tiny Synth open project
// Copyright (C) 2006 miguel angel labolida
// 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 Street, Fifth Floor, Boston, MA 02110-1301 USA.
// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
// implemented with AT89C2051 with 24 MHz and 2k(800h) flash memory
// MIDI input is controlled by the serial interface associated to
// timer 1 in mode 2 (8 bits auto reload).
// The digital oscillator (DCO) frequency is controlled by the
// timer 0 in mode 1 (16 bits without auto reload).
// compiled with sdcc --no-pack-iram
//__code char versn[] = {"_Midi109_"}; // adapt to Tiny 4 ATOM - Leds
//__code char versn[] = {"_Midi110_"}; // sample buffer
//__code char versn[] = {"_Midi111_"}; // ASR envelope signal
__code char versn[] = {"__Midi112__"}; // AR envelope signal
#include <8051.h> // standard 8051 header
#include <string.h>
#define INT_DISABLE (EA = 0) // disable interrupts
#define INT_ENABLE (EA = 1) // enable interrupts
#define UCHAR unsigned char
#define NOTE_ON 0x90 // midi command note on
#define NOTE_OFF 0x80 // midi command note off
// pin 6 P3_2 INT0 portamento
// pin 16 to 19 P1_4 to 7 vave out
#define BUTTON_WAVE P3_1 // pin 3 wave select button
#define LED_1 P3_3 // pin 7 INT1 indicator LED 1
#define LED_2 P3_4 // pin 8 T0 indicator LED 2
#define LED_3 P3_5 // pin 9 T1 indicator LED 3
#define LED_4 P3_7 // pin 11 indicator LED 4
#define AR_REF P1_0 // pin 12 AR envelope reference(+)
#define AR_LEV P1_1 // pin 13 AR envelope comparator(-)
static void dco_ini(void);
static void dco_int(void) interrupt 1 using 2;
static void midi_ini(void);
static void midi_int(void) interrupt 4 using 1;
static __data UCHAR input_byte; // input byte MIDI interface
static __data UCHAR midi_state; // parser automata state
static __data UCHAR note_curr; // current note number
static __data UCHAR note_next; // future note number
static __data UCHAR note_count; // note on counter
static __data UCHAR frqdiv_lo; // freq.divider timer 0 low
static __data UCHAR frqdiv_hi; // freq.divider timer 0 high
static __data UCHAR wave_current; // index current wave 0 to 3
static __data UCHAR wave_sample[16]; // waveform sample table
static __data UCHAR wave_buffer; // wave sample and envelope buffer
// bits 7 - 4 wave high to low
// bit 3 ASR - bit 2 AR
// bit 1 input comp - bit 0 refer.
static __data unsigned char toggle; // DEBUG
#include "freq.c" // frequency divider table
#include "wave.c" // waveform table
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void main()
{
static __data int wave_debounce; // debounce counter
__data unsigned char i; // table notes index
midi_ini();
dco_ini();
IT0 = 1; // portamento
wave_current = 0; // default waveform
LED_1 = 0; // initialize default led
LED_2 = LED_3 = LED_4 = 1; // initialize leds
memcpy(wave_sample, wave_table[0], // load default sample wave
sizeof(wave_sample));
wave_buffer = 0x03; // initialize AR ASR A0 A1 high z
while(1)
{
if (IE0) // INT0 portamento
{ IE0 = 0;
if (note_next > note_curr)
{ note_curr ++;
i = (note_curr - 29)*2; // index of note table
frqdiv_lo = note29[i+1];// freq.divider timer 0 low
frqdiv_hi = note29[i]; // freq.divider timer 0 high
}
if (note_next < note_curr)
{ note_curr --;
i = (note_curr - 29)*2; // index of note table
frqdiv_lo = note29[i+1];// freq.divider timer 0 low
frqdiv_hi = note29[i]; // freq.divider timer 0 high
}
}
if ((! BUTTON_WAVE) // wave selection button on
&& (! wave_debounce)) // debounce complete
{ wave_debounce = 500; // load counter
wave_current ++; // change wave index
wave_current &= 0x03; // truncate
memcpy(wave_sample, // store waveform
wave_table[wave_current],
sizeof(wave_sample));
LED_1 = LED_2 = LED_3 = LED_4 = 1; // initialize leds
switch(wave_current) // preparing
{
case 0: LED_1 = 0; break; // wave leds indicators
case 1: LED_2 = 0; break;
case 2: LED_3 = 0; break;
case 3: LED_4 = 0; break;
}
}
if (BUTTON_WAVE // wave selection button off
&& wave_debounce) // if counter
wave_debounce --; // debounce
if (! P3_6) // analog comparator test
wave_buffer &= ~0x04; // AR envelope off
for (i = 0; i < 10 ;i ++) // delay
{ i = i;
}
}
}
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static void dco_ini(void)
{
INT_DISABLE; // disable interrupts
TMOD &= 0xF0; // clear timer 0 mode bits
TMOD |= 0x01; // timer 0 in mode 1
ET0 = 1; // enable timer 0 interrupt
TR0 = 1; // enable timer 0 counter
INT_ENABLE; // enable interrupts
}
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static void dco_int(void) interrupt 1 using 2
{
static __data UCHAR w_i = 0; // sample index
INT_DISABLE; // disable interrupts
TR0 = 0; // stop timer 0
TH0 = frqdiv_hi; // load timer value high
TL0 = frqdiv_lo; // load timer value low
wave_buffer &= 0x0F; // clear wave bits
wave_buffer |= wave_sample[w_i ++]; // set wave sample
P1 = wave_buffer; // output wave sample
w_i &= 0x0F; // normalize interval 0 - 15
TR0 = 1; // start timer 0
INT_ENABLE; // enable interrupts
}
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static void midi_ini(void)
{
INT_DISABLE;
TR1 = 0; // stop timer
ET1 = 0; // disable timer 1 interrupt
TI = 0; // clear transmit - not used
RI = 0; // clear receiver interrupt
SCON = 0x50; // mode 1 and enable receipt
PCON = 0x80; // smod 1: baudrate doubler
TMOD &= ~0xF0; // clear timer 1 mode bits
TMOD |= 0x20; // timer 1 in mode 2
// baud rate counter = 0xfc
TH1 = (unsigned char)(256 - (24000000L / (16L * 12L * 31250L)));
ES = 1; // enable serial interrupt
TR1 = 1; // enable counter timer 1
INT_ENABLE;
}
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static void midi_int(void) interrupt 4 using 1
{
static __data UCHAR note_temp; // table notes index
__data UCHAR aux_command; // midi command
RI = 0; // reset int. MUST BE 1rst!
input_byte = SBUF; // store input byte
aux_command = input_byte & 0xF0; // clear channel
if (aux_command == NOTE_ON) // midi command parsing
{ midi_state = 1;
return;
}
if (aux_command == NOTE_OFF) // midi command parsing
{ midi_state = 4;
return;
}
if ((midi_state == 1) // midi note number parsing
|| (midi_state == 4)) // for both note on and off
{ midi_state ++; // appoint to next state
note_temp = input_byte; // store future note number
return;
}
if (midi_state == 2) // velocity value parsing
{ midi_state ++; // appoint to next state
if (input_byte) // if greater 0 is note on
{ wave_buffer |= 0x04; // AR envelope on
note_count ++; // increment note on counter
note_next = note_temp; // store future note number
}
else // if velocity 0 is note off
note_count --; // decrease note on counter
}
if (midi_state == 5) // velocity value parsing
{ midi_state ++; // for note off command
note_count --; // decrease note on counter
}
wave_buffer = // set ASR envelope
(note_count) ? wave_buffer | 0x08 // ASR 1
: wave_buffer & ~0x08; // ASR 0 when notes off
}
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