Minor changes

src/main.c

@@ -8,13 +8,16 @@ int main(int argc, char *argv[])
   // Initialize
   MemInit();
   MemLoadROM("../roms/2-ibm-logo.ch8");
+
   ScreenInit(800,400);
   VCPUInit();
-
-  
-  ScreenSetPixel(0,1,1);
+  //  MemDump();
+  int i=0;
   
   while (!WindowShouldClose()){
+    VCPUFetch();
+    VCPUDecode();
+    VCPUExecute();
     ScreenUpdate();
   }
   

src/mem.c

@@ -22,8 +22,9 @@ void MemCopy(unsigned char *data, int size, int addr){
 
 void MemRead(unsigned char *data, int size, int addr){
   int location=addr;
-  for(int i=0;i<size;i++)
+  for(int i=0;i<size;i++){
     data[i]=memory[addr+i];
+  }
 }
 
 void MemLoadROM(char *path){
@@ -38,6 +39,12 @@ void MemLoadROM(char *path){
   fclose(ptr);
 }
 
+void MemDump(){
+  for(int addr=0;addr<4096;addr+=2){
+    printf("0x%03x: %02x %02x\n",addr,memory[addr], memory[addr+1]);
+  }
+}
+
 unsigned char DEFAULT_FONT[]={
 0xF0, 0x90, 0x90, 0x90, 0xF0, // 0
 0x20, 0x60, 0x20, 0x20, 0x70, // 1

src/mem.h

@@ -8,3 +8,4 @@ void MemSet(int addr, unsigned char value, int size);
 void MemCopy(unsigned char *data, int size, int addr);
 void MemRead(unsigned char *data, int size, int addr);
 void MemLoadROM(char *path);
+void MemDump();

src/screen.c

@@ -12,7 +12,8 @@ void ScreenInit(int width, int height){
   Screen.originX=(width-64*Screen.pixel)/2;
   Screen.originY=(height-32*Screen.pixel)/2;
   ScreenClear();
-  
+
+  SetTraceLogLevel(LOG_ERROR); // Disable anoying raylib logs
   InitWindow(width, height, "Chip-8 Emulator");
   SetTargetFPS(60); // Set game to run at 60 frames-per-second
 }
@@ -43,6 +44,13 @@ void ScreenSetPixel(int x, int y, unsigned char state){
   Screen.pixels[x+y*64]=(state==0) ? 0: 1;
 }
 
+void ScreenPixelFlip(int x, int y){
+  if(Screen.pixels[x+y*64]==0)
+    Screen.pixels[x+y*64]=1;
+  else
+    Screen.pixels[x+y*64]=0;
+}
+
 void ScreenClose(){
   CloseWindow(); // Close window and OpenGL context
 }

src/screen.h

@@ -16,5 +16,6 @@ typedef struct SCREEN_DATA {
 void ScreenInit(int width, int height);
 void ScreenClear();
 void ScreenSetPixel(int x, int y, unsigned char state);
+void ScreenPixelFlip(int x, int y);
 void ScreenUpdate();
 void ScreenClose();

src/vcpu.c

@@ -1,7 +1,7 @@
 #include "vcpu.h"
 #include "mem.h"
 #include "screen.h"
-
+#include <stdio.h>
 
 // Current VCPU state
 VCPU_State State;
@@ -11,7 +11,11 @@ void VCPUInit(){
 }
 
 void VCPUFetch(){
-  MemRead((char *)&(State.opcode),2,State.PC);
+  unsigned char byte[2];
+  MemRead(byte,2,State.PC); // Little indian to -1 no +1
+  State.opcode=byte[0];
+  State.opcode=State.opcode<<8;
+  State.opcode=State.opcode | byte[1];
   State.PC+=2;
 }
 
@@ -24,7 +28,7 @@ void VCPUDecode(){
 }
 
 void VCPUExecute(){
-  switch(State.opcode & 0xF){
+  switch(State.opcode >> 12){
   case 0x0:
     ScreenClear();
     break
@@ -45,6 +49,18 @@ void VCPUExecute(){
     State.I=State.NNN;
     break
       ;;
-
+  case 0xD:
+    int X=State.V[State.X]%63;
+    int Y=State.V[State.Y]%31;
+    State.V[0xF]=0; // Set flag to 0
+    for(char row=0;row<State.N;row++){
+      
+    }
+    break;
+    ;;
   }
 }
+
+void VCPUDump(){
+  printf("opcode: 0x%04x\n",State.opcode&0xFFFF);
+}

src/vcpu.h

@@ -21,15 +21,16 @@ typedef struct VCPU_State {
   unsigned char ST;
 
   // Intruction (opcode + decoded fields)
-  short opcode;
+  unsigned short opcode;
   char X;
   char Y;
   char N;
   char NN;
-  short NNN;
+  unsigned short NNN;
 } VCPU_State;
 
 void VCPUInit();
 void VCPUFetch();
 void VCPUDecode();
 void VCPUExecute();
+void VCPUDump();