1 files changed, 156 insertions, 133 deletions

diff --git a/src/uxn/devices/apu.c b/src/uxn/devices/apu.c
index b2ccc18..ba9fe88 100644
--- a/src/uxn/devices/apu.c
+++ b/src/uxn/devices/apu.c
@@ -4,6 +4,7 @@
 #define NOTE_PERIOD (SAMPLE_FREQUENCY * 0x4000 / 11025)
 #define ADSR_STEP (SAMPLE_FREQUENCY / 0xf)
 
+// FIXME: We have two structs for now, needs fixing.
 typedef struct AudioChannel {
     u8 *samples;
     u16 n_samples;
@@ -31,127 +32,22 @@ static APU apu;
 
 
 static u16 pitch_table[] = {
-    12173,
-    11490,
-    10845,
-    10237,
-    9662,
-    9120,
-    8608,
-    8125,
-    7669,
-    7238,
-    6832,
-    6448,
-    6086,
-    5745,
-    5422,
-    5118,
-    4831,
-    4560,
-    4304,
-    4062,
-    3834,
-    3619,
-    3416,
-    3224,
-    3043,
-    2872,
-    2711,
-    2559,
-    2415,
-    2280,
-    2152,
-    2031,
-    1917,
-    1809,
-    1708,
-    1612,
-    1521,
-    1436,
-    1355,
-    1279,
-    1207,
-    1140,
-    1076,
-    1015,
-    958,
-    904,
-    854,
-    806,
-    760,
-    718,
-    677,
-    639,
-    603,
-    570,
-    538,
-    507,
-    479,
-    452,
-    427,
-    403,
-    380,
-    359,
-    338,
-    319,
-    301,
-    285,
-    269,
-    253,
-    239,
-    226,
-    213,
-    201,
-    190,
-    179,
-    169,
-    159,
-    150,
-    142,
-    134,
-    126,
-    119,
-    113,
-    106,
-    100,
-    95,
-    89,
-    84,
-    79,
-    75,
-    71,
-    67,
-    63,
-    59,
-    56,
-    53,
-    50,
-    47,
-    44,
-    42,
-    39,
-    37,
-    35,
-    33,
-    31,
-    29,
-    28,
-    26,
-    25,
-    23,
-    22,
-    21,
-    19,
-    18,
-    17,
-    16,
-    15,
-    14,
-    14,
-    13,
-    12,
-    0,
+    12173, 11490, 10845, 10237, 9662, 9120, 8608, 8125,
+    7669, 7238, 6832, 6448, 6086, 5745, 5422, 5118,
+    4831, 4560, 4304, 4062, 3834, 3619, 3416, 3224,
+    3043, 2872, 2711, 2559, 2415, 2280, 2152, 2031,
+    1917, 1809, 1708, 1612, 1521, 1436, 1355, 1279,
+    1207, 1140, 1076, 1015, 958, 904, 854, 806,
+    760, 718, 677, 639, 603, 570, 538, 507,
+    479, 452, 427, 403, 380, 359, 338, 319,
+    301, 285, 269, 253, 239, 226, 213, 201,
+    190, 179, 169, 159, 150, 142, 134, 126,
+    119, 113, 106, 100, 95, 89, 84, 79,
+    75, 71, 67, 63, 59, 56, 53, 50,
+    47, 44, 42, 39, 37, 35, 33, 31,
+    29, 28, 26, 25, 23, 22, 21, 19,
+    18, 17, 16, 15, 14, 14, 13, 12,
+    2,
 };
 
 void
@@ -188,23 +84,150 @@ reset_sound(AudioChannel *chan) {
     TIMER_CTRL_0 = TIMER_CTRL_ENABLE;
 }
 
-u8 square_wave[] =  {
-    0x00 + 0x80, 0xFF + 0x80
+s8 square_wave[] =  {
+    (s8)0x00 + (s8)0x80, (s8)0xFF + (s8)0x80
 };
+
 #include "text.h"
 
 
+
+//
+//       REG_TM0D                    frequency    buffer size
+//          |                            |            |
+//          V                            V            V
+//
+// Timer = 62610 = 65536 - (16777216 /  5734), buf = 96
+// Timer = 63940 = 65536 - (16777216 / 10512), buf = 176
+// Timer = 64282 = 65536 - (16777216 / 13379), buf = 224
+// Timer = 64612 = 65536 - (16777216 / 18157), buf = 304
+// Timer = 64738 = 65536 - (16777216 / 21024), buf = 352
+// Timer = 64909 = 65536 - (16777216 / 26758), buf = 448
+// Timer = 65004 = 65536 - (16777216 / 31536), buf = 528
+// Timer = 65073 = 65536 - (16777216 / 36314), buf = 608
+// Timer = 65118 = 65536 - (16777216 / 40137), buf = 672
+// Timer = 65137 = 65536 - (16777216 / 42048), buf = 704
+//
+// Source: https://deku.gbadev.org/program/sound1.html
+#define AUDIO_FREQ    18157
+#define AUDIO_BUF_LEN 304
+#define AUDIO_TIMER   64612
+
+typedef struct Audio {
+    s8 mix_buffer[AUDIO_BUF_LEN * 2];
+    s8 *current_buffer;
+    u8 active_buffer;
+} Audio;
+
+typedef struct Channel {
+    // Pointer to the raw data in the ROM.
+    s8 *data;
+    // Current position in the data (20.12 fixed-point).
+    u32 pos;
+    // Increment (20.12 fixed-point).
+    u32 inc;
+    // Volume (0-64, 1.6 fixed-point).
+    u32 vol;
+    // Sound length (20.12 fixed-point).
+    u32 length;
+    // Length of looped portion (20.12 fixed-point, 0 to disable looping).
+    u32 loop_length;
+} Channel;
+
+static Audio audio;
+
+#define POLYPHONY 4
+static Channel channels[POLYPHONY];
+
 void
-init_sound(AudioChannel *chan) {
-    // chan->samples = &square_wave;
-    // chan->n_samples = 2;
-    // chan->samples = &samples;
-    // chan->n_samples = LEN(samples);
-    // chan->pitch++;
-    // chan->pitch = chan->pitch == LEN(pitch_table) - 1 ? 0 : chan->pitch + 1;
-    // chan->loop = true;
-    // chan->sampling_freq = pitch_table[chan->pitch];
-    // txt_printf("RATE: %lu", pitch_table[chan->pitch])
+init_sound(void) {
+    // Initialize audio buffers/channels.
+    audio = (Audio){0};
+    for (size_t i = 0; i < POLYPHONY; ++i) {
+        channels[i] = (Channel){0};
+    }
+
+    // DEBUG: testing channel 0 with square wave
+    channels[0].data = samples;
+    channels[0].inc = (8363 << 12) / AUDIO_FREQ;
+    channels[0].length = (LEN(samples) - 1)  << 12;
+    channels[0].pos = 0;
+    channels[0].vol = 64;
+    channels[0].loop_length = channels[0].length;
+
+    // Enable the sound chip.
+    SOUND_STATUS = SOUND_ENABLE;
+
+    // Set max volume, left-right sound, fifo reset and use timer 0 for
+    // DirectSound A.
+    SOUND_DSOUND_MASTER = SOUND_DSOUND_RATIO_A
+        | SOUND_DSOUND_LEFT_A
+        | SOUND_DSOUND_RIGHT_A
+        | SOUND_DSOUND_RESET_A;
+
+    // TODO: No pitch selection yet.
+    TIMER_DATA_0 = AUDIO_TIMER;
+    TIMER_CTRL_0 = TIMER_CTRL_ENABLE;
+}
+
+void sound_vsync() {
+    // buffer 1 just got over
+    if(audio.active_buffer == 1) {
+        // Start playing buffer 0
+        dma_transfer_copy(SOUND_FIFO_A, audio.mix_buffer, 1, 1,
+                DMA_DST_FIXED | DMA_CHUNK_32 | DMA_REFRESH | DMA_REPEAT | DMA_ENABLE);
+
+        // Set the current buffer pointer to the start of buffer 1
+        audio.current_buffer = audio.mix_buffer + AUDIO_BUF_LEN;
+        audio.active_buffer = 0;
+    } else {
+        // buffer 0 just got over
+        // DMA points to buffer 1 already, so don't bother stopping and resetting it
+        // Set the current buffer pointer to the start of buffer 0
+        audio.current_buffer = audio.mix_buffer;
+        audio.active_buffer = 1;
+    }
+}
+
+void sound_mix() {
+    // Initialize and clear mix_buffer.
+    s16 mix_buffer[AUDIO_BUF_LEN];
+    u32 fill = 0;
+    dma_fill(mix_buffer, fill, sizeof(mix_buffer), 3);
+
+    //  Mix channels into the temporary buffer.
+    for (size_t j = 0; j < POLYPHONY; ++j) {
+        Channel *chan = &channels[j];
+        // Check if channel is active.
+        if (chan->data == NULL) {
+            continue;
+        }
+        for(size_t i = 0; i < AUDIO_BUF_LEN; i++) {
+            // Remember we are using fixed point values.
+            mix_buffer[i] += chan->data[chan->pos >> 12] * chan->vol;
+            chan->pos += chan->inc;
+
+            if (chan->pos >= chan->length) {
+                // If looping is not active disable the channel.
+                if (chan->loop_length == 0) {
+                    chan->data = NULL;
+                    break;
+                }
+
+                // Loop the sample.
+                while (chan->pos >= chan->length) {
+                    chan->pos -= chan->loop_length;
+                }
+            }
+        }
+    }
+
+    // Downsample and copy to the playing buffer.
+    for (size_t i = 0; i < AUDIO_BUF_LEN; ++i) {
+        // >> 8 to divide off the volume, >> 2 to divide by 4 channels to
+        // prevent overflow.
+        audio.current_buffer[i] = mix_buffer[i] >> 8;
+    }
 }
 
 void