Noise channel support

This commit is contained in:
Lior Halphon 2017-08-11 17:57:08 +03:00
parent 1a8bcd314d
commit 0e22ad8eb1
2 changed files with 156 additions and 10 deletions

View File

@ -86,7 +86,7 @@ static void sweep_event(GB_gameboy_t *gb)
{ {
gb->apu.square_channels[GB_SQUARE_1].sample_length = new_sweep_frequency(gb); gb->apu.square_channels[GB_SQUARE_1].sample_length = new_sweep_frequency(gb);
/* Overflow checking only occurs after a delay */ /* Overflow checking only occurs after a delay */
gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.square_carry; gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.lf_div;
gb->apu.square_channels[GB_SQUARE_1].sample_length &= 0x7FF; gb->apu.square_channels[GB_SQUARE_1].sample_length &= 0x7FF;
gb->apu.square_sweep_countdown = ((gb->io_registers[GB_IO_NR10] >> 4) & 7); gb->apu.square_sweep_countdown = ((gb->io_registers[GB_IO_NR10] >> 4) & 7);
@ -140,6 +140,36 @@ void GB_apu_div_event(GB_gameboy_t *gb)
} }
} }
} }
if (gb->apu.noise_channel.length_enabled) {
if (gb->apu.noise_channel.pulse_length) {
if (!--gb->apu.noise_channel.pulse_length) {
gb->apu.is_active[GB_NOISE] = false;
update_sample(gb, GB_NOISE, 0, 0);
}
}
}
uint8_t nr42 = gb->io_registers[GB_IO_NR42];
if (gb->apu.noise_channel.volume_countdown) {
if (!--gb->apu.noise_channel.volume_countdown) {
if ((nr42 & 8) && gb->apu.noise_channel.current_volume < 0xF) {
gb->apu.noise_channel.current_volume++;
}
else if (!(nr42 & 8) && gb->apu.noise_channel.current_volume > 0) {
gb->apu.noise_channel.current_volume--;
}
gb->apu.noise_channel.volume_countdown = (nr42 & 7) * 4;
update_sample(gb, GB_NOISE,
(gb->apu.noise_channel.lfsr & 1) ?
gb->apu.noise_channel.current_volume : 0,
0);
}
}
} }
if ((gb->apu.div_divider & 3) == 3) { if ((gb->apu.div_divider & 3) == 3) {
@ -158,8 +188,9 @@ void GB_apu_run(GB_gameboy_t *gb)
uint8_t cycles = gb->apu.apu_cycles >> 1; uint8_t cycles = gb->apu.apu_cycles >> 1;
gb->apu.apu_cycles = 0; gb->apu.apu_cycles = 0;
if (!cycles) return; if (!cycles) return;
/* To align the square signal to 1MHz */ /* To align the square signal to 1MHz */
gb->apu.square_carry ^= cycles & 1; gb->apu.lf_div ^= cycles & 1;
if (gb->apu.square_sweep_stop_countdown) { if (gb->apu.square_sweep_stop_countdown) {
if (gb->apu.square_sweep_stop_countdown > cycles) { if (gb->apu.square_sweep_stop_countdown > cycles) {
@ -219,6 +250,36 @@ void GB_apu_run(GB_gameboy_t *gb)
} }
} }
if (gb->apu.is_active[GB_NOISE]) {
uint8_t cycles_left = cycles;
while (unlikely(cycles_left > gb->apu.noise_channel.sample_countdown)) {
cycles_left -= gb->apu.noise_channel.sample_countdown + 1;
gb->apu.noise_channel.sample_countdown = gb->apu.noise_channel.sample_length * 2 + 1;
/* Step LFSR */
unsigned high_bit_mask = gb->apu.noise_channel.narrow ? 0x4040 : 0x4000;
// This formula is different on a GBA!
bool new_high_bit = (gb->apu.noise_channel.lfsr ^ (gb->apu.noise_channel.lfsr >> 1) ^ 1) & 1;
gb->apu.noise_channel.lfsr >>= 1;
if (new_high_bit) {
gb->apu.noise_channel.lfsr |= high_bit_mask;
}
else {
/* This code is not redundent, it's relevant when switching LFSR widths */
gb->apu.noise_channel.lfsr &= ~high_bit_mask;
}
update_sample(gb, GB_NOISE,
(gb->apu.noise_channel.lfsr & 1) ?
gb->apu.noise_channel.current_volume : 0,
0);
}
if (cycles_left) {
gb->apu.noise_channel.sample_countdown -= cycles_left;
}
}
if (gb->apu_output.sample_rate) { if (gb->apu_output.sample_rate) {
gb->apu_output.cycles_since_render += cycles; gb->apu_output.cycles_since_render += cycles;
double cycles_per_sample = CPU_FREQUENCY / (double)gb->apu_output.sample_rate; // TODO: this should be cached! double cycles_per_sample = CPU_FREQUENCY / (double)gb->apu_output.sample_rate; // TODO: this should be cached!
@ -267,7 +328,8 @@ void GB_apu_init(GB_gameboy_t *gb)
for (int i = 0; i < 4; i++) { for (int i = 0; i < 4; i++) {
gb->apu.left_enabled[i] = gb->apu.right_enabled[i] = true; gb->apu.left_enabled[i] = gb->apu.right_enabled[i] = true;
} }
gb->apu.square_carry = 1; gb->apu.lf_div = 1;
gb->apu.noise_channel.sample_length = 1;
} }
uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg) uint8_t GB_apu_read(GB_gameboy_t *gb, uint8_t reg)
@ -350,6 +412,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
} }
break; break;
/* Square channels */
case GB_IO_NR10: case GB_IO_NR10:
gb->apu.square_sweep_countdown = ((value >> 4) & 7); gb->apu.square_sweep_countdown = ((value >> 4) & 7);
break; break;
@ -382,7 +445,6 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
break; break;
} }
/* Square channels */
case GB_IO_NR14: case GB_IO_NR14:
case GB_IO_NR24: { case GB_IO_NR24: {
unsigned index = reg == GB_IO_NR24? GB_SQUARE_2: GB_SQUARE_1; unsigned index = reg == GB_IO_NR24? GB_SQUARE_2: GB_SQUARE_1;
@ -392,17 +454,17 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
gb->apu.square_channels[index].current_sample_index = 7; gb->apu.square_channels[index].current_sample_index = 7;
if (!gb->apu.is_active[index]) { if (!gb->apu.is_active[index]) {
gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 6 - gb->apu.square_carry; gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 6 - gb->apu.lf_div;
} }
else { else {
/* Timing quirk: if already active, sound starts 2 (2MHz) ticks earlier. /* Timing quirk: if already active, sound starts 2 (2MHz) ticks earlier.
if both active AND already emitted a sample, sound starts the next 1MHz tick, if both active AND already emitted a sample, sound starts the next 1MHz tick,
and one sample is skipped */ and one sample is skipped */
if (!gb->apu.square_channels[index].sample_emitted) { if (!gb->apu.square_channels[index].sample_emitted) {
gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 4 - gb->apu.square_carry; gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 4 - gb->apu.lf_div;
} }
else { else {
gb->apu.square_channels[index].sample_countdown = gb->apu.square_carry; gb->apu.square_channels[index].sample_countdown = gb->apu.lf_div;
gb->apu.square_channels[index].current_sample_index = 0; gb->apu.square_channels[index].current_sample_index = 0;
} }
} }
@ -419,7 +481,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
if (index == GB_SQUARE_1 && gb->io_registers[GB_IO_NR10] & 7) { if (index == GB_SQUARE_1 && gb->io_registers[GB_IO_NR10] & 7) {
/* APU bug: if shift is nonzero, overflow check also occurs on trigger */ /* APU bug: if shift is nonzero, overflow check also occurs on trigger */
gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.square_carry; gb->apu.square_sweep_stop_countdown = 0x13 - gb->apu.lf_div;
} }
/* Note that we don't change the sample just yet! This was verified on hardware. */ /* Note that we don't change the sample just yet! This was verified on hardware. */
@ -524,6 +586,76 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
break; break;
/* Noise Channel */
case GB_IO_NR41: {
gb->apu.noise_channel.pulse_length = (0x40 - (value & 0x3f));
break;
}
case GB_IO_NR42: {
/* TODO: What happens when changing bits 0-2 after triggering? */
if ((value & 0xF8) == 0) {
/* According to Blargg's test ROM this should disable the channel instantly
TODO: verify how "instant" the change is using PCM34 */
update_sample(gb, GB_NOISE, 0, 0);
gb->apu.is_active[GB_NOISE] = false;
}
break;
}
case GB_IO_NR43: {
gb->apu.noise_channel.narrow = value & 8;
unsigned divisor = (value & 0x07) << 2;
if (!divisor) divisor = 2;
gb->apu.noise_channel.sample_length = (divisor << (value >> 4)) - 1;
break;
}
case GB_IO_NR44: {
if (value & 0x80) {
gb->apu.noise_channel.lfsr = 0;
gb->apu.noise_channel.sample_countdown = (gb->apu.noise_channel.sample_length) * 2 + 4 - gb->apu.lf_div;
if (gb->apu.is_active[GB_NOISE]) {
gb->apu.noise_channel.sample_countdown += 2;
}
gb->apu.noise_channel.current_volume = gb->io_registers[GB_IO_NR42] >> 4;
gb->apu.noise_channel.volume_countdown = (gb->io_registers[GB_IO_NR42] & 7) * 4;
if ((gb->io_registers[GB_IO_NR42] & 0xF8) != 0) {
gb->apu.is_active[GB_NOISE] = true;
}
if (gb->apu.noise_channel.pulse_length == 0) {
gb->apu.noise_channel.pulse_length = 0x40;
gb->apu.noise_channel.length_enabled = false;
}
/* Note that we don't change the sample just yet! This was verified on hardware. */
}
/* APU glitch - if length is enabled while the DIV-divider's LSB is 1, tick the length once. */
if ((value & 0x40) &&
!gb->apu.noise_channel.length_enabled &&
(gb->apu.div_divider & 1) &&
gb->apu.noise_channel.pulse_length) {
gb->apu.noise_channel.pulse_length--;
if (gb->apu.noise_channel.pulse_length == 0) {
if (value & 0x80) {
gb->apu.noise_channel.pulse_length = 0x3F;
}
else {
update_sample(gb, GB_NOISE, 0, 0);
gb->apu.is_active[GB_NOISE] = false;
}
}
}
gb->apu.noise_channel.length_enabled = value & 0x40;
break;
}
default: default:
if (reg >= GB_IO_WAV_START && reg <= GB_IO_WAV_END) { if (reg >= GB_IO_WAV_START && reg <= GB_IO_WAV_END) {
gb->apu.wave_channel.wave_form[(reg - GB_IO_WAV_START) * 2] = value >> 4; gb->apu.wave_channel.wave_form[(reg - GB_IO_WAV_START) * 2] = value >> 4;

View File

@ -40,8 +40,8 @@ typedef struct
uint8_t div_divider; // The DIV register ticks the APU at 512Hz, but is then divided uint8_t div_divider; // The DIV register ticks the APU at 512Hz, but is then divided
// once more to generate 128Hz and 64Hz clocks // once more to generate 128Hz and 64Hz clocks
uint8_t square_carry; // The square channels tick at 1MHz instead of 2, uint8_t lf_div; // The APU runs in 2MHz, but channels 1, 2 and 4 run in 1MHZ so we divide
// so we need a carry to divide the signal // need to divide the signal.
uint8_t square_sweep_countdown; // In 128Hz uint8_t square_sweep_countdown; // In 128Hz
uint8_t square_sweep_stop_countdown; // In 2 MHz uint8_t square_sweep_stop_countdown; // In 2 MHz
@ -73,6 +73,20 @@ typedef struct
int8_t wave_form[32]; int8_t wave_form[32];
bool wave_form_just_read; bool wave_form_just_read;
} wave_channel; } wave_channel;
struct {
uint16_t pulse_length; // Reloaded from NR41 (xorred), in 256Hz DIV ticks
uint8_t current_volume; // Reloaded from NR42
uint8_t volume_countdown; // Reloaded from NR42
uint16_t lfsr;
bool narrow;
uint16_t sample_countdown; // in APU ticks (Reloaded from sample_length)
uint16_t sample_length; // From NR43, in APU ticks
bool length_enabled; // NR44
} noise_channel;
} GB_apu_t; } GB_apu_t;
typedef struct { typedef struct {