#91536 by Matthieu Lalonde (mlalonde)

Theme:
/* NTSC, take 3.14159265
 * -------------------------------------
 * Created Sun Aug 26 14:59:29 EDT 2007
 *
 * (cleft) 2007 by Matthieu Lalonde
 *
 * Note: Ideal values for the resistors are 300ohm and 900ohm.
 *          Using this circuit: http://www.eyetap.org/ece385/vinfo_da00.png
 * Bug(s):
 *      - Jittering of the first one of two lines (should they be skipped?)
 */

#include "WProgram.h"

/**
 * Constants definition
**/
// Debug levels
#define _debugLevelDisable      0
#define _debugLevelGeneric      1
#define _debugLevelSignal       10
#define _debugLevelSimul        20
/**
 * Notes about _debugLevelSignal:
 * 
 * Using this mode you can go through each voltage levels (Sync, black, gray, white).
 * This is useful for testing the circuit as you can make sure the voltages are right by using a multimeter
**/

// Select either of the above debug levels (_debugLevelDisable to disable debugging)
#define _debugMode              _debugLevelGeneric

// Pins definition
#if _debugMode > _debugLevelDisable
#define _pinLED                 5   // Do not use a pin from 8 to 13 or it'll be turn off automatically
#endif
#define _pinSync                8
#define _pinVideo               9

// Definition of signal levels for the AD 2-bit converter
#define _SYNC                   0x00    /* 0.00v */
#define _BLACK                  0x01    /* 0.33v */
#define _GRAY                   0x02    /* 0.67v */
#define _WHITE                  0x03    /* 1.00v */

// Defines TV Modes
#define _NTSC                   1
#define _PAL                    2

// Select a TV mode (PAL isn't implemented, yet)
#define _tvMode                 _NTSC

#if _tvMode == _NTSC
#define _tvNbrLines             262 /* Includes the last 20 lines for the vertical sync! */
#define _tvVSyncNbrLines        20  /* These 20 lines... */

#define _ntscDelayHSyncStart    4.7
#define _ntscDelayBackPorch     6   /* Normally 5.9, but this fixes a timing issue */
#define _ntscDelayFrontPorch    1.4
#define _ntscDelayPerLine       51.5
#define _ntscDelayVSync         58.8
#endif

#if _tvMode == _PAL
    /* Nien */
#endif

#define _tvPixelWidth           21
#define _tvPixelHeight          16

#define _serialBauteRate        19200

/**
 * Prototypes definition
**/
void generateVSync(void);
void writeBufferLine(int position);
void writeTVLines(void);
void clearFrameBuffer(void);
void fillWhiteFrameBuffer(void);
void fillGrayFrameBuffer(void);
void fillPatternFrameBuffer(void);
void loadSprite(void);

/**
 * Variable definition
**/
byte frameBuffer[_tvPixelWidth][_tvPixelHeight];    // Video frame buffer
char c; // Serial buffer

// Defines a static sprite (this could come from EEPROM also)
const static byte graphic[_tvPixelWidth][_tvPixelHeight] = {
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_WHITE,    _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY },
{_BLACK,    _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE,     _BLACK,     _WHITE },
{_GRAY,     _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY,      _GRAY }};

void setup(void) {
    clearFrameBuffer();
    
    pinMode(_pinVideo, OUTPUT);
    pinMode(_pinSync, OUTPUT);
    
#if _debugMode > _debugLevelDisable
    pinMode(_pinLED, OUTPUT);
    digitalWrite(_pinLED, HIGH);
    
    // Draws a dot in the middle
    frameBuffer[(_tvPixelWidth / 2)][(_tvPixelHeight / 2)] = _WHITE;
#endif
    
    Serial.begin(_serialBauteRate);
    Serial.print("Mode: ");
}

void loop(void) {
#if _debugMode < _debugLevelSignal
    // Write the tv lines
    writeTVLines();
#endif
    
    // Check for commands
    if (Serial.available())
    {
        c = Serial.read();
        Serial.println(c);
        
        switch (c)
        {
#if _debugMode < _debugLevelSignal
            case 'w' :
            fillWhiteFrameBuffer();     // Fill the display with white
            break;
            case 'g' :
            fillGrayFrameBuffer();      // Fill the display with gray
            break;
            case 'p' :
            fillPatternFrameBuffer();   // Fill the display with a calculated patter
            break;
            case 'c' :
            clearFrameBuffer();         // Clear the display (all black)
            break;
            case 's' :
            loadSprite();               // Load a sprite to the display
            break;
#else
        /**
            This section is used for sinal debug mode only!
            Use a multimeter to check the tv signal voltages
        **/
            case '1' :
            PORTB   = _SYNC;
            break;
            case '2' :
            PORTB   = _BLACK;
            break;
            case '3' :
            PORTB   = _GRAY;
            break;
            case '4' :
            PORTB   = _WHITE;
            break;
#endif      
            /**
             * Display usage
            **/
            default :
#if _debugMode < _debugLevelSignal
            Serial.println("c: clear screen | p: fill with pattern 1 | s: fill with sprite | w: fill with white | g: fill with gray");
#else
            Serial.println("Debug Levels >> 1: _SYNC | 2: _BLACK | 3: _GRAY | 4: _WHITE");
#endif
            break;
        }
        
        Serial.print("Mode: ");
    }
}

/**
 * Begin the NTSC Specific block
**/
#if _tvMode == _NTSC
/**
    NTSC Signal definition:
     -- Horizontal sync (hsync) pulse: Start each scanline with 0.3V, 
        then 0V for 4.7us (microseconds), and then back to 0.3V. This tells the TV to start drawing a new scanline
        
     -- The "Back Porch": A transition region of 0.3V for 5.9us between the 
        hsync pulse and the visible region, off the left edge of the TV
    
     -- Visible scan region: This is the part you actually see. 
        0.3V shows up as black, 1V as white, everything in between is greyscale. The visible region lasts for 51.5us
    
     -- The "Front Porch": A transition region of 0.3V for 1.4us before 
        the hsync pulse of the next line, off the right edge of the TV
    
     -- Vertical sync (vsync) pulse: Lines 243-262 of each frame (off the bottom of the TV) 
        start with 0.3V for 4.7us, and the rest is 0V. This tells the TV to prepare for a new frame. 
        Think of it as just 0V with an inverted sync pulse

    *** http://www.eyetap.org/ece385/lab5.htm ***
**/

/**
 * Writes every line from what's inside the frameBuffer
 * 
 * Warning: You cannot take the beginning and end sync out of this functions or the sync will fail
 *          (This has been tested on a Mega8)
**/
void writeTVLines(void)
{
    unsigned int i;
    for (i=0;i<(_tvNbrLines - _tvVSyncNbrLines);i++) // Correction for the 20 lines of vertical sync
    {
        /* Begin Line Sync */
        
        // H Sync
        PORTB = _SYNC;
        delayMicroseconds(_ntscDelayHSyncStart);
        
        // Back Porch
        PORTB = _BLACK;
        delayMicroseconds(_ntscDelayBackPorch);

        writeBufferLine(i>>4);  // Visible scan (51.5µs)

        /* End Line Sync (Front Porch) */
        PORTB = _BLACK;
        delayMicroseconds(_ntscDelayFrontPorch);
    }

    // Vertical Sync follows
    generateVSync();    // _tvVSyncNbrLines lines for vertical sync
}

/**
 * Writes each pixel of a line
**/
void writeBufferLine(int position)
{
    unsigned int ii;

    for (ii = 0; ii < _tvPixelWidth; ii++)
    {
        PORTB = frameBuffer[ii][position];

        // Waste some time to make sure the line is sent during the proper timing
        delayMicroseconds((_ntscDelayPerLine / _tvPixelWidth));
    }
}

/**
 * Generate sync pulse for the virtual sync (lasts _tvVSyncNbrLines lines)
**/
void generateVSync(void)
{
    unsigned int ii;
    for (ii = 0; ii < _tvVSyncNbrLines; ii++)
    {
        // Begin V Sync
        PORTB = _BLACK; delayMicroseconds(_ntscDelayHSyncStart);

        PORTB = _SYNC;  delayMicroseconds(_ntscDelayVSync);
    }
}

/**
 * End of the NTSC Specific block
**/
#endif

/**
 * Clears the frame buffer (if mode is true it will fill it with a chess board pattern)
**/
void clearFrameBuffer(void)
{
    byte index, index2;
    
    for (index2 = 0; index2 < _tvPixelHeight; index2++)
    {
        for (index = 0; index < _tvPixelWidth; index++)
        {
            frameBuffer[index][index2] = _BLACK;
        }
    }
}

/**
 * Fills the frame buffer with white
**/ 
void fillWhiteFrameBuffer(void)
{
    byte index, index2;
    
    for (index2 = 0; index2 < _tvPixelHeight; index2++)
    {
        for (index = 0; index < _tvPixelWidth; index++)
        {
            frameBuffer[index][index2] = _WHITE;
        }
    }
}

/**
 * Fills the frame buffer with gray
**/ 
void fillGrayFrameBuffer(void)
{
    byte index, index2;
    
    for (index2 = 0; index2 < _tvPixelHeight; index2++)
    {
        for (index = 0; index < _tvPixelWidth; index++)
        {
            frameBuffer[index][index2] = _GRAY;
        }
    }
}

/**
 * Fills the frame buffer with a pattern
**/ 
void fillPatternFrameBuffer(void)
{
    byte index, index2;
    
    for (index2 = 0; index2 < _tvPixelHeight; index2++)
    {
        for (index = 0; index < _tvPixelWidth; index++)
        {
            frameBuffer[index][index2] = (index + index2) % 3 + 1;
        }
    }
}

/**
 * Copies a sprite to the frameBuffer
**/
void loadSprite(void)
{
    unsigned int ii,jj;
    for (ii=0;ii<_tvPixelWidth;ii++)
    {
        for(jj=0;jj<_tvPixelHeight;jj++)
        {
            frameBuffer[ii][jj] = graphic[ii][jj];
        }
    }
}