Speaker sound buffer to generate perfect square waves

A2Mac.xcodeproj/project.pbxproj

@@ -427,8 +427,8 @@
 		32A9F7472467B5DF004902A1 /* audio */ = {
 			isa = PBXGroup;
 			children = (
-				32A9F7492467B60B004902A1 /* speaker.c */,
 				32A9F7482467B60B004902A1 /* speaker.h */,
+				32A9F7492467B60B004902A1 /* speaker.c */,
 			);
 			path = audio;
 			sourceTree = "<group>";

src/cpu/6502.c

@@ -713,10 +713,6 @@ void softReset() {
 
 void m6502_Run() {
     
-    // clear speaker buffer, so we can fill it up by new data
-    memset(spkr_samples, 127, spkr_buf_size);
-    
-    
     // init time
 //#ifdef CLK_WAIT
 //    unsigned long long elpased = (unsigned long long)-1LL;
@@ -778,7 +774,11 @@ void m6502_Run() {
     }
     
     spkr_play();
+    // clear speaker buffer, so we can fill it up by new data
+    memset(spkr_samples, spkr_level, spkr_buf_size);
     
+    
+
 }
 
 void read_rom( const char * bundlePath, const char * filename, uint8_t * rom, const uint16_t addr ) {

src/dev/audio/speaker.c

@@ -48,6 +48,10 @@ ALCcontext *ctx = NULL;
 ALuint spkr_buf = 0;
 ALuint spkr_src = 0;
 
+// we start with the max, because otherwise the speaker clicks
+uint8_t spkr_level = SPKR_LEVEL_MAX;
+
+
 const int spkr_seconds = 1;
 const unsigned spkr_sample_rate = 44100;
 const unsigned spkr_buf_size = spkr_seconds * spkr_sample_rate;
@@ -64,7 +68,7 @@ void spkr_init() {
     alcMakeContextCurrent(ctx);
     
     // Fill buffer with zeros
-    memset( spkr_samples, 127, spkr_buf_size );
+    memset( spkr_samples, spkr_level, spkr_buf_size );
     
 }
 
@@ -112,4 +116,6 @@ void spkr_play() {
     alSourcei(spkr_src, AL_LOOPING, 0);
     
     alSourcePlay(spkr_src);
+    
+    memset(spkr_samples, spkr_level, spkr_buf_size);
 }

src/dev/audio/speaker.h

@@ -11,6 +11,8 @@
 
 #include <stdio.h>
 
+#define SPKR_LEVEL_MIN      0
+#define SPKR_LEVEL_MAX      127
 
 extern void spkr_init(void);
 extern void spkr_exit(void);
@@ -19,5 +21,8 @@ extern void spkr_play(void);
 extern const unsigned spkr_buf_size;
 extern char spkr_samples [];
 
+extern uint8_t spkr_level;
+
+
 
 #endif /* speaker_h */

src/dev/mem/mmio.h

@@ -48,7 +48,6 @@ uint8_t * const RDHIMEM = Apple2_64K_MEM;       // Pointer to the Shadow Memory
 uint8_t * const WRHIMEM = Apple2_Dummy_RAM;     // Pointer to the Shadow Memory Map so we can use this from Swift
 
 
-
 #define DEF_RAM_PAGE(mem,pg) \
     (mem) + ((pg) << 8)
 
@@ -401,6 +400,35 @@ void auxMemorySelect() {
 }
 
 
+INLINE void spkr_switch() {
+    // TODO: This is very slow!
+    //            printf("io_KBDSTRB\n");
+    
+    // push a click into the speaker buffer
+    // (we will play the entire buffer at the end of the frame)
+    int sample_idx = clkfrm / 22;
+    if ( spkr_level > SPKR_LEVEL_MIN ) {
+        spkr_level = SPKR_LEVEL_MIN;
+    }
+    else {
+        spkr_level = SPKR_LEVEL_MAX;
+    }
+    //spkr_samples[sample_idx] = spkr_level;
+    memset(spkr_samples + sample_idx, spkr_level, spkr_buf_size - sample_idx);
+    
+    //ViewController_spk_up_play();
+    
+    
+    //        case io_VID_CLR80VID:
+    //            videoMode.col80 = 0;
+    //            break;
+    //
+    //        case io_VID_SET80VID:
+    //            videoMode.col80 = 1;
+    //            break;
+    //
+}
+
 
 INLINE uint8_t ioRead( uint16_t addr ) {
 //    if (outdev) fprintf(outdev, "ioRead:%04X\n", addr);
@@ -419,28 +447,10 @@ INLINE uint8_t ioRead( uint16_t addr ) {
             Apple2_64K_RAM[io_KBD] &= 0x7F;
             return Apple2_64K_RAM[io_KBDSTRB];
 
-        case (uint8_t)io_SPKR: {
-            // TODO: This is very slow!
-//            printf("io_KBDSTRB\n");
-         
-            // push a click into the speaker buffer
-            // (we will play the entire buffer at the end of the frame)
-            int sample_idx = clkfrm / 22;
-            spkr_samples[sample_idx] = 0;
-            
-            //ViewController_spk_up_play();
-            
+        case (uint8_t)io_SPKR:
+            spkr_switch();
             return Apple2_64K_RAM[io_SPKR];
 
-//        case io_VID_CLR80VID:
-//            videoMode.col80 = 0;
-//            break;
-//
-//        case io_VID_SET80VID:
-//            videoMode.col80 = 1;
-//            break;
-//
-        }
         case (uint8_t)io_VID_RDTEXT:
             return videoMode.text << 7;
             
@@ -699,6 +709,10 @@ INLINE void ioWrite( uint16_t addr, uint8_t val ) {
             Apple2_64K_RAM[io_KBD] &= 0x7F;
             break;
             
+        case io_SPKR:
+            spkr_switch();
+            break;
+            
         case io_RDMAINRAM:
 //            printf("io_RDMAINRAM\n");
             MEMcfg.RD_AUX_MEM = 0;