cga.ino

#define HSYNC 8
#define VSYNC 16
#define ROWS 261

const byte buf[1][200] = {
  { 0, 5, 4, 3, 2, 1, 6, 7, 1, 2 , 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2 /* 100 */, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2, 0, 5, 4, 3, 2, 1, 6, 7, 1, 2 /* 200 */ }
};

#define SETC(x) PORTB = (PORTB & ~7) | x

#define EXEC_NOP asm volatile ("nop\n\t")
#define EXEC_10_NOPS EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP;
#define EXEC_50_NOPS EXEC_10_NOPS; EXEC_10_NOPS; EXEC_10_NOPS; EXEC_10_NOPS; EXEC_10_NOPS;
#define EXEC_100_NOPS EXEC_50_NOPS; EXEC_50_NOPS;

#define EXEC_LEFT_BLANKING_AND_OVERSCAN() { EXEC_50_NOPS; SETC(0); EXEC_10_NOPS; EXEC_NOP; EXEC_NOP; EXEC_NOP; }
#define EXEC_RIGHT_OVERSCAN_AND_BLANKING() { SETC(0); EXEC_50_NOPS; EXEC_50_NOPS; EXEC_10_NOPS; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; EXEC_NOP; }
#define EXEC_HSYNC() { PORTB |= HSYNC; EXEC_50_NOPS; EXEC_10_NOPS; EXEC_10_NOPS; EXEC_NOP; PORTB &= ~HSYNC; }

#define DRAW_PIXELS_FOR_LINE(i) { \
  SETC(buf[i][0]);          \
  SETC(buf[i][1]);          \
  SETC(buf[i][2]);          \ 
  SETC(buf[i][3]);          \
  SETC(buf[i][4]);          \
  SETC(buf[i][5]);          \
  SETC(buf[i][6]);          \
  SETC(buf[i][7]);          \
  SETC(buf[i][8]);          \
  SETC(buf[i][9]);          \
  SETC(buf[i][10]);         \
  SETC(buf[i][11]);         \ 
  SETC(buf[i][12]);         \ 
  SETC(buf[i][13]);         \
  SETC(buf[i][14]);         \
  SETC(buf[i][15]);         \
  SETC(buf[i][16]);         \
  SETC(buf[i][17]);         \
  SETC(buf[i][18]);         \
  SETC(buf[i][19]);         \
  SETC(buf[i][20]);         \
  SETC(buf[i][21]);         \ 
  SETC(buf[i][22]);         \ 
  SETC(buf[i][23]);         \
  SETC(buf[i][24]);         \
  SETC(buf[i][25]);         \
  SETC(buf[i][26]);         \
  SETC(buf[i][27]);         \
  SETC(buf[i][28]);         \
  SETC(buf[i][29]);         \ 
  SETC(buf[i][30]);         \ 
  SETC(buf[i][31]);         \
  SETC(buf[i][32]);         \ 
  SETC(buf[i][33]);         \
  SETC(buf[i][34]);         \
  SETC(buf[i][35]);         \
  SETC(buf[i][36]);         \
  SETC(buf[i][37]);         \
  SETC(buf[i][38]);         \
  SETC(buf[i][39]);         \
  SETC(buf[i][40]);         \
  SETC(buf[i][41]);         \
  SETC(buf[i][42]);         \ 
  SETC(buf[i][43]);         \
  SETC(buf[i][44]);         \
  SETC(buf[i][45]);         \
  SETC(buf[i][46]);         \
  SETC(buf[i][47]);         \
  SETC(buf[i][48]);         \
  SETC(buf[i][49]);         \
  SETC(buf[i][50]);         \
  SETC(buf[i][51]);         \
  SETC(buf[i][52]);         \ 
  SETC(buf[i][53]);         \
  SETC(buf[i][54]);         \
  SETC(buf[i][55]);         \
  SETC(buf[i][56]);         \
  SETC(buf[i][57]);         \
  SETC(buf[i][58]);         \
  SETC(buf[i][59]);         \
  SETC(buf[i][60]);         \
  SETC(buf[i][61]);         \
  SETC(buf[i][62]);         \ 
  SETC(buf[i][63]);         \
  SETC(buf[i][64]);         \
  SETC(buf[i][65]);         \
  SETC(buf[i][66]);         \
  SETC(buf[i][67]);         \
  SETC(buf[i][68]);         \
  SETC(buf[i][69]);         \
  SETC(buf[i][70]);         \
  SETC(buf[i][71]);         \
  SETC(buf[i][72]);         \ 
  SETC(buf[i][73]);         \
  SETC(buf[i][74]);         \
  SETC(buf[i][75]);         \
  SETC(buf[i][76]);         \
  SETC(buf[i][77]);         \
  SETC(buf[i][78]);         \
  SETC(buf[i][79]);         \
  SETC(buf[i][80]);         \
  SETC(buf[i][81]);         \
  SETC(buf[i][82]);         \ 
  SETC(buf[i][83]);         \
  SETC(buf[i][84]);         \
  SETC(buf[i][85]);         \
  SETC(buf[i][86]);         \
  SETC(buf[i][87]);         \
  SETC(buf[i][78]);         \
  SETC(buf[i][89]);         \
  SETC(buf[i][90]);         \
  SETC(buf[i][91]);         \
  SETC(buf[i][92]);         \ 
  SETC(buf[i][93]);         \
  SETC(buf[i][94]);         \
  SETC(buf[i][95]);         \
  SETC(buf[i][96]);         \
  SETC(buf[i][97]);         \
  SETC(buf[i][98]);         \
  SETC(buf[i][99]);         \
  SETC(buf[i][100]);        \
  SETC(buf[i][101]);        \
  SETC(buf[i][102]);        \ 
  SETC(buf[i][103]);        \
  SETC(buf[i][104]);        \
  SETC(buf[i][105]);        \
  SETC(buf[i][106]);        \
  SETC(buf[i][107]);        \
  SETC(buf[i][108]);        \
  SETC(buf[i][109]);        \
  SETC(buf[i][110]);        \
  SETC(buf[i][111]);        \
  SETC(buf[i][112]);        \ 
  SETC(buf[i][113]);        \
  SETC(buf[i][114]);        \
  SETC(buf[i][115]);        \
  SETC(buf[i][116]);        \
  SETC(buf[i][117]);        \
  SETC(buf[i][118]);        \
  SETC(buf[i][119]);        \
  SETC(buf[i][120]);        \
  SETC(buf[i][121]);        \ 
  SETC(buf[i][122]);        \ 
  SETC(buf[i][123]);        \
  SETC(buf[i][124]);        \
  SETC(buf[i][125]);        \
  SETC(buf[i][126]);        \
  SETC(buf[i][127]);        \
  SETC(buf[i][128]);        \
  SETC(buf[i][129]);        \
  SETC(buf[i][130]);        \
  SETC(buf[i][131]);        \
  SETC(buf[i][132]);        \ 
  SETC(buf[i][133]);        \
  SETC(buf[i][134]);        \
  SETC(buf[i][135]);        \
  SETC(buf[i][136]);        \
  SETC(buf[i][137]);        \
  SETC(buf[i][138]);        \
  SETC(buf[i][139]);        \
  SETC(buf[i][140]);        \
  SETC(buf[i][141]);        \
  SETC(buf[i][142]);        \ 
  SETC(buf[i][143]);        \
  SETC(buf[i][144]);        \
  SETC(buf[i][145]);        \
  SETC(buf[i][146]);        \
  SETC(buf[i][147]);        \
  SETC(buf[i][148]);        \
  SETC(buf[i][149]);        \
  SETC(buf[i][150]);        \
  SETC(buf[i][151]);        \
  SETC(buf[i][152]);        \ 
  SETC(buf[i][153]);        \
  SETC(buf[i][154]);        \
  SETC(buf[i][155]);        \
  SETC(buf[i][156]);        \
  SETC(buf[i][157]);        \
  SETC(buf[i][158]);        \
  SETC(buf[i][159]);        \
  SETC(buf[i][160]);        \
  SETC(buf[i][161]);        \
  SETC(buf[i][162]);        \ 
  SETC(buf[i][163]);        \
  SETC(buf[i][164]);        \
  SETC(buf[i][165]);        \
  SETC(buf[i][166]);        \
  SETC(buf[i][167]);        \
  SETC(buf[i][168]);        \
  SETC(buf[i][169]);        \
  SETC(buf[i][170]);        \
  SETC(buf[i][171]);        \
  SETC(buf[i][172]);        \ 
  SETC(buf[i][173]);        \
  SETC(buf[i][174]);        \
  SETC(buf[i][175]);        \
  SETC(buf[i][176]);        \
  SETC(buf[i][177]);        \
  SETC(buf[i][178]);        \
  SETC(buf[i][179]);        \
  SETC(buf[i][180]);        \
  SETC(buf[i][181]);        \
  SETC(buf[i][182]);        \ 
  SETC(buf[i][183]);        \
  SETC(buf[i][184]);        \
  SETC(buf[i][185]);        \
  SETC(buf[i][186]);        \
  SETC(buf[i][187]);        \
  SETC(buf[i][178]);        \
  SETC(buf[i][189]);        \
  SETC(buf[i][190]);        \
  SETC(buf[i][191]);        \
  SETC(buf[i][192]);        \ 
  SETC(buf[i][193]);        \
  SETC(buf[i][194]);        \
  SETC(buf[i][195]);        \
  SETC(buf[i][196]);        \
  SETC(buf[i][197]);        \
  SETC(buf[i][198]);        \
  SETC(buf[i][199]);        \
}

#define DRAW_LINE(i) { \
  EXEC_LEFT_BLANKING_AND_OVERSCAN(); \
  DRAW_PIXELS_FOR_LINE(i); \
  EXEC_RIGHT_OVERSCAN_AND_BLANKING(); \
  EXEC_HSYNC(); \
}

int row = ROWS;

void setup() {
    DDRB = B111111;
    PORTB &= ~(HSYNC | VSYNC | 7);
    noInterrupts();
}

void loop() {
  DRAW_LINE(0);

  switch (row++) {
      case 225:
          PORTB |= VSYNC; // VSYNC HIGH
          break;
      case 228:
          PORTB &= ~VSYNC; // VSYNC LOW
          break;
      case 261:
          row = 0;
          break;
  }
}