Merge pull request #127 from gwilymk/make-it-easier-to-configure-sound-frequencies

Make it easier to configure sound frequencies

agb-sound-converter/Cargo.toml

@@ -17,6 +17,9 @@ debug = true
 [lib]
 proc-macro = true
 
+[features]
+freq18157 = []
+
 [dependencies]
 hound = "3.4.0"
 syn = "1.0.73"

agb-sound-converter/src/lib.rs

@@ -12,6 +12,11 @@ use std::{
 };
 use syn::parse_macro_input;
 
+#[cfg(not(feature = "freq18157"))]
+const FREQUENCY: u32 = 10512;
+#[cfg(feature = "freq18157")]
+const FREQUENCY: u32 = 18157;
+
 #[proc_macro]
 pub fn include_wav(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as syn::LitStr);
@@ -43,8 +48,9 @@ pub fn include_wav(input: TokenStream) -> TokenStream {
 
             assert_eq!(
                 wav_reader.spec().sample_rate,
-                10512,
-                "agb currently only supports sample rate of 10512Hz"
+                FREQUENCY,
+                "agb currently only supports sample rate of {}Hz",
+                FREQUENCY
             );
 
             let samples = samples_from_reader(wav_reader);

agb/Cargo.toml

@@ -17,6 +17,7 @@ debug = true
 [features]
 default = ["alloc"]
 alloc = []
+freq18157 = ["agb_sound_converter/freq18157"]
 
 [dependencies]
 bitflags = "1.2"

agb/crt0.s

@@ -64,5 +64,5 @@ b .Initialise_mb
     b 1b
 .pool
 
-.include "src/sound/mixer/mixer.s"
 .include "interrupt_handler.s"
+.include "src/sound/mixer/mixer.s"

agb/src/sound/mixer/mixer.s

@@ -1,4 +1,8 @@
-.equ SOUND_BUFFER_SIZE, 176
+.section .iwram
+    .global agb_rs__buffer_size
+    .balign 4
+agb_rs__buffer_size:
+    .word
 
 agb_arm_func agb_rs__mixer_add
     @ Arguments
@@ -19,8 +23,8 @@ agb_arm_func agb_rs__mixer_add
 modifications_fallback:
     orr r7, r7, r3, lsl #16   @ r7 now is the left channel followed by the right channel modifications.
 
-    mov r5, #0               @ current index we're reading from
-    mov r8, #SOUND_BUFFER_SIZE @ the number of steps left
+    mov r5, #0                   @ current index we're reading from
+    ldr r8, agb_rs__buffer_size @ the number of steps left
 
 
 1:
@@ -62,8 +66,8 @@ same_modification:
     lsrs r7, r7, #1
     bne 1b
 
-    mov r5, #0               @ current index we're reading from
-    mov r8, #SOUND_BUFFER_SIZE @ the number of steps left
+    mov r5, #0                   @ current index we're reading from
+    ldr r8, agb_rs__buffer_size @ the number of steps left
 
 .macro mixer_add_loop_simple
     add r4, r0, r5, asr #8    @ calculate the address of the next read from the sound buffer
@@ -132,7 +136,7 @@ agb_arm_func agb_rs__mixer_add_stereo
     str r4, [r1], #4         @ store the new value, and increment the pointer
 .endm
 
-    mov r8, #SOUND_BUFFER_SIZE
+    ldr r8, agb_rs__buffer_size
 1:
     mixer_add_loop_simple_stereo
     mixer_add_loop_simple_stereo
@@ -159,8 +163,10 @@ agb_arm_func agb_rs__mixer_collapse
     @ Arguments:
     @ r0 = target buffer (i8)
     @ r1 = input buffer (i16) of fixnums with 4 bits of precision (read in sets of i16 in an i32)
+    push {r4}
 
-    mov r2, #SOUND_BUFFER_SIZE @ loop counter
+    ldr r2, agb_rs__buffer_size @ loop counter
+    mov r4, r2
 
 1:
     @ r12 = *r1; r1++
@@ -173,11 +179,12 @@ agb_arm_func agb_rs__mixer_collapse
     clamp_s8 r12            @ clamp the audio to 8 bit values
     clamp_s8 r3
 
-    strb r3, [r0, #SOUND_BUFFER_SIZE] @ *(r0 + SOUND_BUFFER_SIZE) = r3
+    strb r3, [r0, r4] @ *(r0 + r4 = SOUND_BUFFER_SIZE) = r3
     strb r12, [r0], #1                @ *r0 = r12; r0++
 
     subs r2, r2, #1      @ r2 -= 1
     bne 1b               @ loop if not 0
 
+    pop {r4}
     bx lr
-agb_arm_end agb_rs__mixer_collapse
+agb_arm_end agb_rs__mixer_collapse

agb/src/sound/mixer/sw_mixer.rs

@@ -91,9 +91,26 @@ impl Mixer {
 
 // I've picked one frequency that works nicely. But there are others that work nicely
 // which we may want to consider in the future: http://deku.gbadev.org/program/sound1.html
+#[cfg(not(feature = "freq18157"))]
 const SOUND_FREQUENCY: i32 = 10512;
+#[cfg(not(feature = "freq18157"))]
 const SOUND_BUFFER_SIZE: usize = 176;
 
+#[cfg(feature = "freq18157")]
+const SOUND_FREQUENCY: i32 = 18157;
+#[cfg(feature = "freq18157")]
+const SOUND_BUFFER_SIZE: usize = 304;
+
+fn set_asm_buffer_size() {
+    extern "C" {
+        static mut agb_rs__buffer_size: usize;
+    }
+
+    unsafe {
+        agb_rs__buffer_size = SOUND_BUFFER_SIZE;
+    }
+}
+
 #[repr(C, align(4))]
 struct SoundBuffer([i8; SOUND_BUFFER_SIZE * 2]);
 
@@ -106,6 +123,8 @@ struct MixerBuffer {
 
 impl MixerBuffer {
     fn new() -> Self {
+        set_asm_buffer_size();
+
         MixerBuffer {
             buffer1: SoundBuffer([0; SOUND_BUFFER_SIZE * 2]),
             buffer2: SoundBuffer([0; SOUND_BUFFER_SIZE * 2]),