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-rw-r--r--src/mame/audio/redbaron.c213
1 files changed, 213 insertions, 0 deletions
diff --git a/src/mame/audio/redbaron.c b/src/mame/audio/redbaron.c
new file mode 100644
index 00000000000..5df88d0ad15
--- /dev/null
+++ b/src/mame/audio/redbaron.c
@@ -0,0 +1,213 @@
+/*************************************************************************
+
+ Atari Red Baron hardware
+
+*************************************************************************/
+/*
+
+ Red Baron sound notes:
+ bit function
+ 7-4 explosion volume
+ 3 start led
+ 2 shot (machine gun sound)
+ 1 squeal (nosedive sound)
+ 0 POTSEL (rb_input_select)
+*/
+
+#include <math.h>
+#include "driver.h"
+#include "streams.h"
+#include "bzone.h"
+#include "sound/custom.h"
+#include "sound/pokey.h"
+
+#define OUTPUT_RATE (48000)
+
+/* Statics */
+static INT16 *vol_lookup = NULL;
+
+static INT16 vol_crash[16];
+
+static sound_stream *channel;
+static int latch;
+static int poly_counter;
+static int poly_shift;
+
+static int filter_counter;
+
+static int crash_amp;
+static int shot_amp;
+static int shot_amp_counter;
+
+static int squeal_amp;
+static int squeal_amp_counter;
+static int squeal_off_counter;
+static int squeal_on_counter;
+static int squeal_out;
+
+WRITE8_HANDLER( redbaron_sounds_w )
+{
+ /* If sound is off, don't bother playing samples */
+ if( data == latch )
+ return;
+
+ stream_update(channel);
+ latch = data;
+ rb_input_select = data & 1;
+}
+
+WRITE8_HANDLER( redbaron_pokey_w )
+{
+ if( latch & 0x20 )
+ pokey1_w (offset, data);
+}
+
+static void redbaron_sound_update(void *param, stream_sample_t **inputs, stream_sample_t **outputs, int length)
+{
+ stream_sample_t *buffer = outputs[0];
+ while( length-- )
+ {
+ int sum = 0;
+
+ /* polynome shifter E5 and F4 (LS164) clocked with 12kHz */
+ poly_counter -= 12000;
+ while( poly_counter <= 0 )
+ {
+ poly_counter += OUTPUT_RATE;
+ if( ((poly_shift & 0x0001) == 0) == ((poly_shift & 0x4000) == 0) )
+ poly_shift = (poly_shift << 1) | 1;
+ else
+ poly_shift <<= 1;
+ }
+
+ /* What is the exact low pass filter frequency? */
+ filter_counter -= 330;
+ while( filter_counter <= 0 )
+ {
+ filter_counter += OUTPUT_RATE;
+ crash_amp = (poly_shift & 1) ? latch >> 4 : 0;
+ }
+ /* mix crash sound at 35% */
+ sum += vol_crash[crash_amp] * 35 / 100;
+
+ /* shot not active: charge C32 (0.1u) */
+ if( (latch & 0x04) == 0 )
+ shot_amp = 32767;
+ else
+ if( (poly_shift & 0x8000) == 0 )
+ {
+ if( shot_amp > 0 )
+ {
+ /* discharge C32 (0.1u) through R26 (33k) + R27 (15k)
+ * 0.68 * C32 * (R26 + R27) = 3264us
+ */
+// #define C32_DISCHARGE_TIME (int)(32767 / 0.003264);
+ /* I think this is to short. Is C32 really 1u? */
+ #define C32_DISCHARGE_TIME (int)(32767 / 0.03264);
+ shot_amp_counter -= C32_DISCHARGE_TIME;
+ while( shot_amp_counter <= 0 )
+ {
+ shot_amp_counter += OUTPUT_RATE;
+ if( --shot_amp == 0 )
+ break;
+ }
+ /* mix shot sound at 35% */
+ sum += vol_lookup[shot_amp] * 35 / 100;
+ }
+ }
+
+
+ if( (latch & 0x02) == 0 )
+ squeal_amp = 0;
+ else
+ {
+ if( squeal_amp < 32767 )
+ {
+ /* charge C5 (22u) over R3 (68k) and CR1 (1N914)
+ * time = 0.68 * C5 * R3 = 1017280us
+ */
+ #define C5_CHARGE_TIME (int)(32767 / 1.01728);
+ squeal_amp_counter -= C5_CHARGE_TIME;
+ while( squeal_amp_counter <= 0 )
+ {
+ squeal_amp_counter += OUTPUT_RATE;
+ if( ++squeal_amp == 32767 )
+ break;
+ }
+ }
+
+ if( squeal_out )
+ {
+ /* NE555 setup as pulse position modulator
+ * C = 0.01u, Ra = 33k, Rb = 47k
+ * frequency = 1.44 / ((33k + 2*47k) * 0.01u) = 1134Hz
+ * modulated by squeal_amp
+ */
+ squeal_off_counter -= (1134 + 1134 * squeal_amp / 32767) / 3;
+ while( squeal_off_counter <= 0 )
+ {
+ squeal_off_counter += OUTPUT_RATE;
+ squeal_out = 0;
+ }
+ }
+ else
+ {
+ squeal_on_counter -= 1134;
+ while( squeal_on_counter <= 0 )
+ {
+ squeal_on_counter += OUTPUT_RATE;
+ squeal_out = 1;
+ }
+ }
+ }
+
+ /* mix sequal sound at 40% */
+ if( squeal_out )
+ sum += 32767 * 40 / 100;
+
+ *buffer++ = sum;
+ }
+}
+
+void *redbaron_sh_start(int clock, const struct CustomSound_interface *config)
+{
+ int i;
+
+ vol_lookup = (INT16 *)auto_malloc(32768 * sizeof(INT16));
+ for( i = 0; i < 0x8000; i++ )
+ vol_lookup[0x7fff-i] = (INT16) (0x7fff/exp(1.0*i/4096));
+
+ for( i = 0; i < 16; i++ )
+ {
+ /* r0 = R18 and R24, r1 = open */
+ double r0 = 1.0/(5600 + 680), r1 = 1/6e12;
+
+ /* R14 */
+ if( i & 1 )
+ r1 += 1.0/8200;
+ else
+ r0 += 1.0/8200;
+ /* R15 */
+ if( i & 2 )
+ r1 += 1.0/3900;
+ else
+ r0 += 1.0/3900;
+ /* R16 */
+ if( i & 4 )
+ r1 += 1.0/2200;
+ else
+ r0 += 1.0/2200;
+ /* R17 */
+ if( i & 8 )
+ r1 += 1.0/1000;
+ else
+ r0 += 1.0/1000;
+ r0 = 1.0/r0;
+ r1 = 1.0/r1;
+ vol_crash[i] = 32767 * r0 / (r0 + r1);
+ }
+
+ channel = stream_create(0, 1, OUTPUT_RATE, 0, redbaron_sound_update);
+
+ return auto_malloc(1);
+}