[WIP] Initial implementation of CH3 envelope

4 files changed, 69 insertions, 11 deletions

diff --git a/Makefile b/Makefile
index 4686168..6a33d16 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@ INC_FLAGS   := $(addprefix -I,$(INC_DIRS))
 INC_FLAGS   += -I$(LIBGBA_SRC)
 
 # Output library names and executables.
-TARGET         := STEPPER-v1.8-dev-09
+TARGET         := STEPPER-v1.8-dev-11
 ELF            := $(BUILD_DIR)/$(TARGET).elf
 BIN            := $(BUILD_DIR)/$(TARGET).gba
 
diff --git a/src/assets.c b/src/assets.c
index 94c9de2..c11364e 100644
--- a/src/assets.c
+++ b/src/assets.c
@@ -92,9 +92,14 @@ enum WAVES {
     WAVE_MAX,
 };
 
+#define WAVE_SIZE 4
 #define WAVE_VARS 4
 
-typedef u32 Wave[WAVE_VARS];
+typedef u32 Wave[WAVE_SIZE];
+static Wave wave_active = {0};
+static Wave wave_target = {0};
+static int wave_env_ticks = 0;
+static int wave_env_decay = 8;
 
 static const Wave waves[][WAVE_VARS] = {
     {
diff --git a/src/main.c b/src/main.c
index 5e18396..a8c93bf 100644
--- a/src/main.c
+++ b/src/main.c
@@ -34,6 +34,8 @@ WITH REGARD TO THIS SOFTWARE.
 //  - Make sure transposing a sequence past the keyboard limit doesn't affect
 //    the sequence and can be reversed.
 //  - Study saving overhauls for bootleg cartridges.
+//  - When putting a new trigger, make sure it uses the global parameters
+//  - Bad performance when selecting patterns
 //
 // Low priority:
 //
diff --git a/src/sequencer.c b/src/sequencer.c
index 981bbc6..01b8e95 100644
--- a/src/sequencer.c
+++ b/src/sequencer.c
@@ -229,14 +229,16 @@ play_step(void) {
         if (trig->active && should_play(params->prob)) {
             switch (params->wave_mode) {
                 case 0: {
+                    memcpy32(wave_active, waves[params->shape_a][params->type_a], 16);
                     SOUND_WAVE_MODE = SOUND_WAVE_BANK_SELECT(1);
-                    memcpy32(SOUND_WAVE_RAM, waves[params->shape_a][params->type_a], 16);
+                    memcpy32(SOUND_WAVE_RAM, wave_active, 16);
                     SOUND_WAVE_MODE = SOUND_WAVE_BANK_MODE(0)
                         | SOUND_WAVE_BANK_SELECT(0);
                 } break;
                 case 1: {
+                    memcpy32(wave_active, waves[params->shape_b][params->type_b], 16);
                     SOUND_WAVE_MODE = SOUND_WAVE_BANK_SELECT(0);
-                    memcpy32(SOUND_WAVE_RAM, waves[params->shape_b][params->type_b], 16);
+                    memcpy32(SOUND_WAVE_RAM, wave_active, 16);
                     SOUND_WAVE_MODE = SOUND_WAVE_BANK_MODE(0)
                         | SOUND_WAVE_BANK_SELECT(1);
                 } break;
@@ -249,6 +251,7 @@ play_step(void) {
                         | SOUND_WAVE_BANK_SELECT(0);
                 } break;
             }
+            wave_env_ticks = 0;
             SOUND_WAVE_MODE |= SOUND_WAVE_ENABLE;
 
             SOUND_WAVE_FREQ = SOUND_FREQ_RESET
@@ -261,12 +264,6 @@ play_step(void) {
                 case 4: { SOUND_WAVE_CTRL = SOUND_WAVE_VOL_100; } break;
             }
             pan[2] = params->pan;
-        } else {
-            // NOTE: Maybe in the future we want an AD, but for now this is
-            // probably better than holding the notes. Or perhaps add a hold
-            // mode?
-            SOUND_WAVE_FREQ = SOUND_FREQ_RESET;
-            SOUND_WAVE_CTRL = SOUND_WAVE_MUTE;
         }
     } else {
         SOUND_WAVE_FREQ = SOUND_FREQ_RESET;
@@ -352,11 +349,65 @@ play_step(void) {
 
 static int nseq_ticks = 0;
 
+IWRAM_CODE
+void
+wave_ad_tick(void) {
+    // Play a single step for A+B or no envelope.
+    if ((SOUND_WAVE_MODE & SOUND_WAVE_BANK_MODE(1)) || !wave_env_decay) {
+        if (wave_env_ticks++ == 24) {
+            SOUND_WAVE_FREQ = SOUND_FREQ_RESET;
+            SOUND_WAVE_CTRL = SOUND_WAVE_MUTE;
+        }
+        return;
+    }
+
+    if (wave_env_ticks++ < wave_env_decay) {
+        return;
+    }
+    wave_env_ticks = 0;
+
+    // Decay.
+    for (size_t j = 0; j < 4; j++) {
+        u32 next = 0;
+        for (size_t i = 0; i < 8; i++) {
+            u8 val = (wave_active[j] >> 4 * i) & 0xF;
+            // Operating in 24.8 fixed point:
+            // 0.9 = 230; 0.8 = 205; 0.75 = 192
+            int power = 205;
+            if (val < 0x7) {
+                int tmp = 0x7 - val;
+                tmp *= power;
+                tmp >>= 8;
+                val = (0x7 - tmp) & 0xf;
+            } else if (val > 0x7) {
+                int tmp = (val - 0x7);
+                tmp *= power;
+                tmp >>= 8;
+                val = tmp + 0x7;
+                if (val <= 0x7) {
+                    val = 0x7;
+                }
+            }
+            next |= (val << 4 * i);
+        }
+        wave_active[j] = next;
+    }
+
+    // DEBUG:
+    // int x = 50;
+    // int y = 50;
+    // draw_filled_rect(0 + x, 0 + y, 100 + x, 32 + y, COL_BG);
+    // draw_wave_pattern(&wave_active, 0 + x, 0 + y, 1);
+
+    memcpy32(SOUND_WAVE_RAM, wave_active, 16);
+    SOUND_WAVE_MODE ^= SOUND_WAVE_BANK_SELECT(1);
+}
+
 void
 sequencer_tick(void) {
+    wave_ad_tick();
     if (nseq_ticks++ == 0) {
         play_step();
-        return;
     } else if (nseq_ticks == 24) {
         nseq_ticks = 0;
     }