[wrap]
/*
Battlezone sound info, courtesy of Al Kossow:
D7 motor enable this enables the engine sound
D6 start LED
D5 sound enable this enables ALL sound outputs
including the POKEY output
D4 engine rev en this controls the engine speed
the engine sound is an integrated square
wave (saw tooth) that is frequency modulated
by engine rev.
D3 shell loud, soft/ explosion volume
D2 shell enable
D1 explosion loud, soft/ explosion volume
D0 explosion enable gates a noise generator
*/
#include <math.h>
#include "driver.h"
#include "streams.h"
#include "bzone.h"
#include "sound/custom.h"
#define OUTPUT_RATE (6000*4)
/* Statics */
static INT16 *discharge = NULL;
#define EXP(charge,n) (charge ? 0x7fff - discharge[0x7fff-n] : discharge[n])
static sound_stream *channel;
static int latch;
static int poly_counter;
static int poly_shift;
static int explosion_clock;
static int explosion_out;
static int explosion_amp;
static int explosion_amp_counter;
static int shell_clock;
static int shell_out;
static int shell_amp;
static int shell_amp_counter;
static int motor_counter;
static int motor_counter_a;
static int motor_counter_b;
static int motor_rate;
static int motor_rate_new;
static int motor_rate_counter;
static int motor_amp;
static int motor_amp_new;
static int motor_amp_step;
static int motor_amp_counter;
WRITE8_HANDLER( bzone_sounds_w )
{
if( data == latch )
return;
stream_update(channel);
latch = data;
sound_global_enable(latch & 0x20);
}
static STREAM_UPDATE( bzone_sound_update )
{
stream_sample_t *buffer = outputs[0];
while( samples-- )
{
static int last_val = 0;
int sum = 0;
/* polynome shifter H5 and H4 (LS164) clocked with 6kHz */
poly_counter -= 6000;
while( poly_counter <= 0 )
{
int clock;
poly_counter += OUTPUT_RATE;
if( ((poly_shift & 0x0008) == 0) == ((poly_shift & 0x4000) == 0) )
poly_shift = (poly_shift << 1) | 1;
else
poly_shift <<= 1;
/* NAND gate J4 */
clock = ((poly_shift & 0x7000) == 0x7000) ? 0 : 1;
/* raising edge on pin 3 of J5 (LS74)? */
if( clock && !explosion_clock )
explosion_out ^= 1;
/* save explo clock level */
explosion_clock = clock;
/* input 11 of J5 (LS74) */
clock = (poly_shift >> 15) & 1;
/* raising edge on pin 11 of J5 (LS74)? */
if( clock && !shell_clock )
shell_out ^= 1;
/* save shell clock level */
shell_clock = clock;
}
/* explosion enable: charge C14 */
if( latch & 0x01 )
explosion_amp = 32767;
/* explosion output? */
if( explosion_out )
{
if( explosion_amp > 0 )
{
/*
* discharge C14 through R17 + R16
* time constant is 10e-6 * 23000 = 0.23 seconds
* (samples were decaying much slower: 1/4th rate? )
*/
explosion_amp_counter -= (int)(32767 / (0.23*4));
if( explosion_amp_counter < 0 )
{
int n = (-explosion_amp_counter / OUTPUT_RATE) + 1;
explosion_amp_counter += n * OUTPUT_RATE;
if( (explosion_amp -= n) < 0 )
explosion_amp = 0;
}
}
/*
* I don't know the amplification of the op-amp
* and feedback, so the loud/soft values are arbitrary
*/
if( latch & 0x02 ) /* explosion loud ? */
sum += EXP(0,explosion_amp)/3;
else
sum += EXP(0,explosion_amp)/4;
}
/* shell enable: charge C9 */
if( latch & 0x04 )
shell_amp = 32767;
/* shell output? */
if( shell_out )
{
if( shell_amp > 0 )
{
/*
* discharge C9 through R14 + R15
* time constant is 4.7e-6 * 23000 = 0.1081 seconds
* (samples were decaying much slower: 1/4th rate? )
*/
shell_amp_counter -= (int)(32767 / (0.1081*4));
if( shell_amp_counter < 0 )
{
int n = (-shell_amp_counter / OUTPUT_RATE) + 1;
shell_amp_counter += n * OUTPUT_RATE;
if( (shell_amp -= n) < 0 )
shell_amp = 0;
}
}
/*
* I don't know the amplification of the op-amp
* and feedback, so the loud/soft values are arbitrary
*/
if( latch & 0x08 ) /* shell loud ? */
sum += EXP(0,shell_amp)/3;
else
sum += EXP(0,shell_amp)/4;
}
if( latch & 0x80 )
{
/* NE5555 timer
* C = 0.018u, Ra = 100k, Rb = 125k
* charge time = 0.693 * (Ra + Rb) * C = 3870us
* discharge time = 0.693 * Rb * C = 1559.25us
* freq approx. 184 Hz
* I have no idea what frequencies are coming from the NE555
* with "MOTOR REV EN" being high or low. I took 240Hz as
* higher rate and sweep up or down to the new rate in 0.25s
*/
motor_rate_new = (latch & 0x10) ? 240 : 184;
if( motor_rate != motor_rate_new )
{
/* sweep rate to new rate */
motor_rate_counter -= (int)((240 - 184) / 0.25);
while( motor_rate_counter <= 0 )
{
motor_rate_counter += OUTPUT_RATE;
motor_rate += (motor_rate < motor_rate_new) ? +1 : -1;
}
}
motor_counter -= motor_rate;
while( motor_counter <= 0 )
{
double r0, r1;
motor_counter += OUTPUT_RATE;
r0 = 1.0/1e12;
r1 = 1.0/1e12;
if( ++motor_counter_a == 16 )
motor_counter_a = 6;
if( ++motor_counter_b == 16 )
motor_counter_b = 4;
if( motor_counter_a & 8 ) /* bit 3 */
r1 += 1.0/33000;
else
r0 += 1.0/33000;
if( motor_counter_a == 15 ) /* ripple carry */
r1 += 1.0/33000;
else
r0 += 1.0/33000;
if( motor_counter_b & 8 ) /* bit 3 */
r1 += 1.0/33000;
else
r0 += 1.0/33000;
if( motor_counter_b == 15 ) /* ripple carry */
r1 += 1.0/33000;
else
r0 += 1.0/33000;
/* new voltage at C29 */
r0 = 1.0/r0;
r1 = 1.0/r1;
motor_amp_new = (int)(32767 * r0 / (r0 + r1));
/* charge/discharge C29 (0.47uF) */
if( motor_amp_new > motor_amp )
motor_amp_step = (int)((motor_amp_new - motor_amp) / (r1*0.47e-6));
else
motor_amp_step = (int)((motor_amp - motor_amp_new) / (r0*0.47e-6));
}
if( motor_amp != motor_amp_new )
{
motor_amp_counter -= motor_amp_step;
if( motor_amp_counter < 0 )
{
int n = (-motor_amp_counter / OUTPUT_RATE) + 1;
motor_amp_counter += n * OUTPUT_RATE;
if( motor_amp > motor_amp_new )
{
motor_amp -= n;
if( motor_amp < motor_amp_new )
motor_amp = motor_amp_new;
}
else
{
motor_amp += n;
if( motor_amp > motor_amp_new )
motor_amp = motor_amp_new;
}
}
}
sum += EXP((motor_amp<motor_amp_new),motor_amp)/3;
}
*buffer++ = (sum + last_val) / 2;
/* crude 75% low pass filter */
last_val = (sum + last_val * 3) / 4;
}
}
CUSTOM_START( bzone_sh_start )
{
int i;
discharge = (INT16 *)auto_malloc(32768 * sizeof(INT16));
for( i = 0; i < 0x8000; i++ )
discharge[0x7fff-i] = (INT16) (0x7fff/exp(1.0*i/4096));
channel = stream_create(device, 0, 1, OUTPUT_RATE, 0, bzone_sound_update);
return auto_malloc(1);
}
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