diff options
Diffstat (limited to 'src/mame/audio/redbaron.c')
-rw-r--r-- | src/mame/audio/redbaron.c | 213 |
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); +} |