chip8

commit 9e2576c23ce5be167f71d74abba55c89cf2e2d86
parent 3651261430c0bf2512b45438288bb72b562e52d7
Author: Léo Villeveygoux <l@vgx.fr>
Date:   Sat,  4 May 2019 03:00:03 +0200

Add sound support

440Hz unsigned 8bit saw waves using plain SDL audio.

Diffstat:
M
chip8.c
 | 
2
++
M
media-sdl.c
 | 
39
+++++++++++++++++++++++++++++++++++++++
M
media.h
 | 
1
+

3 files changed, 42 insertions(+), 0 deletions(-)
diff --git a/chip8.c b/chip8.c
@@ -383,6 +383,8 @@ int main(int argc, char **argv){
 			if(ST)
 				ST--;
 		}
+		set_buzzer_state(ST ? 1 : 0);
+
 		printf("i=%5d, DT=%3d, K=[", i, (int)DT);
 		for(int k=0 ; k<16;k++)
 			printf("%s", KEYBOARD & 1<<k ? "1":"0");
diff --git a/media-sdl.c b/media-sdl.c
@@ -13,6 +13,12 @@
 #define WINDOW_NAME "CHIP-8 emulator"
 
 #define NUM_PIXELS (SCREEN_WIDTH*SCREEN_HEIGHT)
+
+#define SOUND_DEV_FREQ 48000
+#define SOUND_SAMPLES 1024
+#define BUZZER_FREQ 440
+#define BUZZER_VOL .05
+
 unsigned char *pixels;
 
 SDL_Window *window;
@@ -20,6 +26,10 @@ SDL_Renderer *renderer;
 SDL_Texture *texture;
 SDL_Rect rect = {.x=0,.y=0,.w=SCREEN_WIDTH,.h=SCREEN_HEIGHT};
 
+/* sound state*/
+int buzzer_state = 0;
+long sample_num = 0;
+
 unsigned clock;
 
 /*
@@ -43,6 +53,18 @@ SDL_Keycode keys[16] = {
 	SDLK_6, SDLK_y, SDLK_h, SDLK_n
 };
 
+static void buzzer_callback(void* userdata, Uint8* stream, int len){
+	(void) userdata;
+	for(int i=0 ; i<len ; i++){
+		if(buzzer_state == 0)
+			stream[i] = 0;
+		else /* saw waves at the moment */
+			stream[i] =
+				((sample_num++*256*BUZZER_FREQ/SOUND_DEV_FREQ)
+				 %256)*BUZZER_VOL;
+	}
+}
+
 int m_init(int argc, char **argv){
 	(void)argc, (void)argv;
 	/*TODO: check every init */
@@ -67,6 +89,16 @@ int m_init(int argc, char **argv){
 
 	SDL_RenderClear(renderer);
 
+	SDL_OpenAudio(&(SDL_AudioSpec){
+			.freq = SOUND_DEV_FREQ,
+			.format = AUDIO_U8,
+			.channels = 1,
+			.samples = SOUND_SAMPLES,
+			.callback = buzzer_callback,
+			}, NULL);
+
+	SDL_PauseAudio(0);
+
 	clock = SDL_GetTicks();	
 
 	return 0;
@@ -76,6 +108,9 @@ void m_quit(void){
 	SDL_DestroyTexture(texture);
 	SDL_DestroyRenderer(renderer);
 	SDL_DestroyWindow(window);
+
+	SDL_CloseAudio();
+
 	SDL_Quit();
 
 	free(pixels);
@@ -142,6 +177,10 @@ void send_draw(void){
 	SDL_RenderClear(renderer);
 }
 
+void set_buzzer_state(int state){
+	buzzer_state = state;
+}
+
 void wait_tick(void){
 	/* TODO: tunable frequency */
 	unsigned new_clock = SDL_GetTicks();
diff --git a/media.h b/media.h
@@ -11,6 +11,7 @@ unsigned short wait_input(unsigned short input);
 void clear_screen(void);
 void draw(int x, int y, int value);
 void send_draw(void);
+void set_buzzer_state(int state);
 
 void wait_tick(void);