add sound

README.md

@@ -14,7 +14,7 @@ This is a CHIP-8 interpreter, built with SDL2. It mimics the CHIP-8 system and i
 
 [This general high-level guide](https://tobiasvl.github.io/blog/write-a-chip-8-emulator) is what got me into making this. It was a lot of fun! I suggest you try it too.
 
-[Here](https://github.com/loktar00/chip8/tree/master/roms) is the source of the roms. I do not own or claim ownership of these files. They are only present in this repository for educational purposes.
+[Here](https://github.com/loktar00/chip8/tree/master/roms) is the source of the all the roms. I just renamed them to making testing easier. I do not own or claim ownership of these files. They are only present in this repository for educational purposes.
 
 ## TODO
 

include/chip8.h

@@ -2,7 +2,7 @@
 #define CHIP8_H
 
 // CHIP-8 system variables
-// (NOTE: chars are 8-bits, shorts are 16-bits)
+// NOTE: chars are 8-bits, shorts are 16-bits
 struct chip8
 {
     unsigned short opcode;      // current operation code

include/sdlutils.h

@@ -8,10 +8,12 @@ typedef struct
 {
     SDL_Window *window;
     SDL_Renderer *renderer;
+    SDL_AudioDeviceID audio;
 } SDLComponents;
 
 int initSDL(SDLComponents *components);
 void redrawDisplay(SDLComponents *components, struct chip8 *chip8);
 void destroySDL(SDLComponents *components);
+void playSound();
 
 #endif

src/chip8.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include "../include/chip8.h"
+#include "../include/sdlutils.h"
 
 #define F 0xF // the 16th V register is for the carry flag
 
@@ -169,6 +170,7 @@ void cycle(struct chip8 *chip8)
     case 0xC000: // CXNN: Sets VX to the result of a bitwise AND operation on a random number and NN
                  // just need to make sure that the random number fits in 8-bits
         chip8->V[X] = (rand() % 256) & NN;
+        chip8->pc += 2;
         break;
     case 0xD000: // DXYN: Draws a sprite at coordinate (VX, VY) that has a width of 8 pixels and a height of N pixels
         unsigned short x = chip8->V[X];
@@ -210,6 +212,7 @@ void cycle(struct chip8 *chip8)
         {
         case 0x0007: // FX07: Sets VX to the value of the delay timer
             chip8->V[X] = chip8->delayTimer;
+            chip8->pc += 2;
             break;
         case 0x000A: // FX0A: A key press is awaited, and then stored in VX
             for (int i = 0; i < 16; i++)
@@ -224,17 +227,21 @@ void cycle(struct chip8 *chip8)
             return;  // if no key is pressed, return without incrementing the program counter
         case 0x0015: // FX15: Sets the delay timer to VX
             chip8->delayTimer = chip8->V[X];
+            chip8->pc += 2;
             break;
         case 0x0018: // FX18: Sets the sound timer to VX
             chip8->soundTimer = chip8->V[X];
+            chip8->pc += 2;
             break;
         case 0x001E: // FX1E: Adds VX to I
             chip8->I += chip8->V[X];
+            chip8->pc += 2;
             break;
         case 0x0029: // FX29: Sets I to the location of the sprite for the character in VX
                      // Characters 0-F (in hexadecimal) are represented by a 4x5 font
                      // so to move the I to the correct location, we need to multiply the value of VX by 5
             chip8->I = chip8->V[X] * 0x5;
+            chip8->pc += 2;
             break;
         case 0x0033:                                                // FX33: Stores the binary-coded decimal representation of VX at the addresses I, I plus 1, and I plus 2
             chip8->memory[chip8->I] = chip8->V[X] / 100;            // fetches the hundreds digit:  X00
@@ -272,7 +279,7 @@ void cycle(struct chip8 *chip8)
     {
         if (chip8->soundTimer == 1)
         {
-            // play a sound
+            playSound();
         }
         chip8->soundTimer--;
     }

src/main.c

@@ -20,7 +20,7 @@ int main()
     initKeymap();
 
     // load ROM
-    loadRom(&chip8, "roms/IBMLogo.ch8");
+    loadRom(&chip8, "roms/Pong.ch8");
 
     // main loop
     while (1)
@@ -46,7 +46,7 @@ int main()
             chip8.drawFlag = 0;
         }
 
-        SDL_Delay(100);
+        SDL_Delay(10);
     }
     destroySDL(&components);
     return 0;

src/sdlutils.c

@@ -1,9 +1,15 @@
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
 #include "../include/sdlutils.h"
 #include "../include/chip8.h"
 
+static SDL_AudioDeviceID *audioPointer;
+
 int initSDL(SDLComponents *components)
 {
-    if (SDL_Init(SDL_INIT_VIDEO) < 0)
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO) < 0)
     {
         printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
         return 1;
@@ -31,6 +37,25 @@ int initSDL(SDLComponents *components)
         return 1;
     }
 
+    // setup audio
+    SDL_AudioSpec want, have;
+    SDL_zero(want);
+    want.freq = 44100;
+    want.format = AUDIO_S16SYS;
+    want.channels = 1;
+    want.samples = 2048;
+    want.callback = NULL;
+
+    // open audio
+    components->audio = SDL_OpenAudioDevice(NULL, 0, &want, &have, 0);
+    if (components->audio == 0)
+    {
+        printf("Failed to open audio device! SDL_Error: %s\n", SDL_GetError());
+        return 1;
+    }
+
+    audioPointer = &components->audio;
+
     return 0;
 }
 
@@ -61,3 +86,28 @@ void destroySDL(SDLComponents *components)
     SDL_DestroyWindow(components->window);
     SDL_Quit();
 }
+
+void playSound()
+{
+    // params
+    int freq = 440;          // frequency
+    int samples = 2048;      // number of samples to generate
+    int sample_rate = 44100; // sample rate
+
+    // sound generation
+    int16_t *sound = malloc(samples * sizeof(int16_t));
+    for (int i = 0; i < samples; i++)
+    {
+        sound[i] = 32767.0 * sin(2.0 * M_PI * freq * i / sample_rate);
+    }
+
+    // play the sound
+    SDL_QueueAudio(*audioPointer, sound, samples * sizeof(int16_t));
+    SDL_PauseAudioDevice(*audioPointer, 0);
+
+    // wait for the sound to finish playing
+    SDL_Delay(samples * 1000 / sample_rate);
+
+    // free the sound
+    free(sound);
+}