#91188 by Matthieu Lalonde (mlalonde)

Theme:
/* NTSC, take 2
 * ---------------
 * Created Sun Aug 26 14:59:29 EDT 2007
 *
 * (cleft) 2007 by Matthieu Lalonde
 *
 * Note: Ideal values for the resistors are 900ohm and 330ohm!
 * 
 */
#include "WProgram.h"

#define _debugMode          true

// Définition des pins
#define _pinSync            8
#define _pinVideo           9
#define _pinLED             12

// 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)
#define _tvMode             _NTSC

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

#define _tvPixelWidth       21
#define _tvPixelHeight      16

#define _serialBauteRate    19200

// Prototypes
void startHSync(void);
void endHSync(void);
void generateVSync(void);
void writeBufferLine(int position);
void writeTVLines(void);
void clearFrameBuffer(boolean mode);

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

#ifdef _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 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 with proper timing
        if (_tvPixelWidth < 51)
            delayMicroseconds((51.5 / _tvPixelWidth));
        else
            delayMicroseconds((_tvPixelWidth / 51.5));
    }
}

// Generate sync pulse for a new line
void startHSync(void)
{
    // Begin H Sync
    PORTB = _SYNC;  delayMicroseconds(4.7);
    
    // Back Porch
    PORTB = _BLACK; delayMicroseconds(5.9);
    
    // Visible scan (51.5µs) follows
}

// Generate sync pulse for the end of a line
void endHSync(void)
{
    // Front Porch
    PORTB = _BLACK; delayMicroseconds(1.4);
}

// Generate sync pulse for the virtual sync (lasts 20 lines)
void generateVSync(void)
{
    unsigned int ii;
    for (ii = 0; ii < _tvVSyncNbrLines; ii++)
    {
        // Begin V Sync
        PORTB = _BLACK; delayMicroseconds(4.7);

        PORTB = _SYNC;  delayMicroseconds(58.8);
    }
}
#endif

// Writes every line from what's inside the frameBuffer
void writeTVLines(void)
{
    unsigned int i;
    for (i=0;i<(_tvNbrLines - _tvVSyncNbrLines);i++) // Includes correction for the vertical sync
    {
        startHSync();
        
        // Write the line
        writeBufferLine(i>>4);
        
        endHSync();
    }
    
    // Vertical Sync
    generateVSync();
}

// Clears the frame buffer (if mode is true it will fill it with a chess board pattern)
void clearFrameBuffer(boolean mode)
{
    byte index, index2;
    
    for (index2 = 0; index2 < _tvPixelHeight; index2++)
    {
        for (index = 0; index < _tvPixelWidth; index++)
        {
            if (!mode) {
                frameBuffer[index][index2] = _BLACK;
            } else {
                frameBuffer[index][index2] = (index + index2) % 3 + 1;
            }
        }
    }
}

// Defines a static sprite
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) {
    Serial.begin(_serialBauteRate);
    Serial.println("Arduino Initialized!");
    Serial.println((long int) (sizeof frameBuffer));
    
    Serial.print("Mode: ");
    
    pinMode(_pinVideo, OUTPUT);
    pinMode(_pinSync, OUTPUT);
    
    clearFrameBuffer(false);
    frameBuffer[(_tvPixelWidth / 2)][(_tvPixelHeight / 2)] = _WHITE;
}

void loop(void) {
    // Write the tv lines
    writeTVLines();
    
    // Check for commands
    if (Serial.available())
    {
        c = Serial.read();
        switch (c)
        {
            case 'c' :
            Serial.println(); Serial.println("Clearing screen");
            clearFrameBuffer(false);
            break;
            
            case 'f' :
            Serial.println(); Serial.println("Filling with pattern");
            clearFrameBuffer(true);
            break;
            
            case 'g' :
            Serial.println(); Serial.println("Filling with graphic");
            int ii,jj;
            for (ii=0;ii<_tvPixelWidth;ii++)
            {
                for(jj=0;jj<_tvPixelHeight;jj++)
                {
                    frameBuffer[ii][jj] = graphic[ii][jj];
                }
            }
            break;
            default :
            Serial.println();
            Serial.println("c: clear screen | f: fille with pattern 1 | g: fill graphic pattern");
            break;
        }
        
        Serial.print("Mode: ");
    }
}