}}}
= Arduino TV =
After seeing someone on the [http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1176757335/0 Arduino forums] use the microcontroller to do [http://en.wikipedia.org/wiki/PAL/ PAL] TV output, I wanted to give it a shot. The technique is fairly simple and uses as little as two digital IO ports. The code has been totally rewritten and adapted to the [http://en.wikipedia.org/wiki/NTSC NTSC standard]. This project never went very far because lacking an oscilloscope and experience in ASM, it became clear that I would be unable to achieve perfect timing which is necessary for video output. Furthermore, the ATMega168 lacks the necessary RAM space to provide a decent frame buffer. I have still learned much from this project which appeared on the [http://blog.makezine.com/archive/2007/08/arduino_tv.html Make blog]. Would I have had more resources to spend on this project I would have liked to use ASM and timer interrupts for better synchronizing and to expand it with gray levels using more IO pins.
== Bibliography ==
* [http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1187659197 Arduino Pong]
* [http://www.stanford.edu/class/ee281/handouts/lab4.pdf]
* [http://vimeo.com/288344]
* [http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1188261175/0 Interfacing with an NTSC TV] forum thread
* [http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1176757335/0 Vidéo avec Arduino, afficher sur moniteur] forum thread (in French)
* [http://blog.makezine.com/archive/2007/08/arduino_tv.html Arduino TV ] post in the Makezine blog featuring my NTSC code.
== Circuit ==
[[Image(http://instruct1.cit.cornell.edu/courses/ee476/video/VideoDAC.png)]]
== Source code ==
You can also download a [/basedoc/NTSC.pde plain text] copy.
{{{
#!cpp
/**
* NTSC, revision 4
* -------------------------------------
* Created Sun Aug 26 14:59:29 EDT 2007
*
* (cleft) 2007 by Matthieu Lalonde
* Some rights reserved under a Creative Commons By-Sa 2.5
* http://creativecommons.org/licenses/by-nc-sa/2.5/ca/
*
* Notes:
* You can still use pins 10 to 13 as digital outputs (however, no pwn or input ! ).
* This is done through the use of "_SIGNAL | (PORTB & B00111100)"
*
* Known Issues:
* If you put the resolution higher than ~21x16, the uC seems to crash
* Sometimes the uC acts as if the mode (output) had not been set properly.
* (Re-uploading seemed to have fixed the problem when I've seen it.)
* Going into signal mode sometimes seems to crash the uC (same behavior as the first issue).
*
* Circuit:
* Use this circuit: http://www.eyetap.org/ece385/vinfo_da00.png
* Ideal values for the resistors are 300ohm and 900ohm.
*
* Bibliography & Reference:
* Documentation: http://www.eyetap.org/ece385/lab5.htm
* Thanks to Binarymillenium for his video (http://vimeo.com/288344) explaining common sync problems.
* Thanks to Benoit Rousseau for the original PAL code & research
* Thanks to MAKE who featured this project on the blog and pushed me to continue
* Thanks to Ikaruga for his help with testing
*
* Associated forum thread:
* http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1188261175
*
**/
#include "WProgram.h"
/**
* Constants definition
**/
#define NOP PORTB = PORTB /* For some reason, I can seem to access NOP properly! This does the job */
// 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 B00010000
#endif
#define _pinSync 8
#define _pinVideo 9
// Defines signal levels for the 2 bit DAC
/* Arduin pin mapping: nn111100
aa321098 */
#define _SYNC B00000000 /* 0.00v */
#define _BLACK B00000001 /* 0.33v */
#define _GRAY B00000010 /* 0.67v */
#define _WHITE B00000011 /* 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 _tvRefreshRate 60 /* Hertz */
/**
* Note about timings. I believe they are all rounded as they are converter to ints!
*/
#define _ntscLineLength 63.3 /* Could be 63.625 */
#define _ntscDelayHSyncStart 4.7
#define _ntscDelayBackPorch 5.9
#define _ntscDelayFrontPorch 1.4
#define _ntscDelayPerLine 51.5
#define _ntscDelayVSync 50 /* Normally this would be 58.8, but it's apparently too long */
#endif
#if _tvMode == _PAL
/* Nada */
#endif
#define _tvPixelWidth 21 /* This _cannot_ be higher than the number of lines! */
#define _tvPixelHeight 16
#define _serialBauteRate 115200
/**
* Prototypes definition
**/
void generateVSync(void);
void writeBufferLine(unsigned char position);
void writeTVLines(void);
void fillFrameBufferWith(byte _level);
void clearFrameBuffer(void);
void fillWhiteFrameBuffer(void);
void fillGrayFrameBuffer(void);
void fillPatternFrameBuffer(void);
void fillRandomFrameBuffer(void);
void setPixel(byte x, byte y, byte val);
void loadSprite(byte* graphic);
/**
* Variable definition
**/
char serialBuffer; // Serial buffer
byte frameBuffer[_tvPixelWidth][_tvPixelHeight]; // Video frame buffer
byte linesPerPixel = _tvNbrLines / _tvPixelHeight; // Contains the number of lines per pixels
// Defines a static sprite (this could come from EEPROM also but it's a bad idea to load into the ram)
/*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) {
//cli(); /* Disabled in wiring.c */
// Enables port. As of now Arduino pins 8 to 13 are all inputs!
DDRB = B00111111;
PORTB = _SYNC; // Turn all pins off
#ifdef _pinLED
if (_pinLED < 8) digitalWrite(_pinLED, HIGH);
else PORTB = (_pinLED & B00111100);
#endif
#if _debugMode > _debugLevelDisable
fillRandomFrameBuffer();
#else
clearFrameBuffer();
#endif
Serial.begin(_serialBauteRate);
Serial.print("Mode: ");
}
//unsigned int previousMillis, interval;
//interval = 1000/_tvRefreshRate;
void loop(void) {
#if _debugMode < _debugLevelSignal
// Write the tv lines
//if (millis() - previousMillis > interval) {
// previousMillis = millis();
writeTVLines();
//}
#endif
// Check for commands
if (Serial.available())
{
serialBuffer = Serial.read();
Serial.println(serialBuffer);
switch (serialBuffer)
{
#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 'r' :
fillRandomFrameBuffer(); // Load a sprite to the display
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 | (PORTB & B00111100);
break;
case '2' :
PORTB = _BLACK | (PORTB & B00111100);
break;
case '3' :
PORTB = _GRAY | (PORTB & B00111100);
break;
case '4' :
PORTB = _WHITE | (PORTB & B00111100);
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: ");
}
}
#if _tvMode == _NTSC
/**
* Begin the NTSC Specific block
* *******************************
*
* 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 char i, j, k;
j = 0;
k = 0;
for (i=0;i<(_tvNbrLines - _tvVSyncNbrLines);i++) // Correction for the 20 lines of vertical sync
{
/* Begin Line Sync */
// H Sync
PORTB = _SYNC | (PORTB & B00111100);
delayMicroseconds(_ntscDelayHSyncStart);
// Back Porch
PORTB = _BLACK | (PORTB & B00111100);
delayMicroseconds(_ntscDelayBackPorch);
writeBufferLine(j); // Visible scan (51.5µs)
/* End Line Sync (Front Porch) */
PORTB = _BLACK | (PORTB & B00111100);
delayMicroseconds(_ntscDelayFrontPorch);
if (i == (k + linesPerPixel))
{
k = i;
j++;
}
}
// Vertical Sync follows
generateVSync();
}
/**
* Writes each pixel of a line
**/
void writeBufferLine(unsigned char position)
{
unsigned char ii = _tvPixelWidth;
byte lineDelay = (_ntscDelayPerLine - _tvPixelWidth) / _tvPixelWidth;
while (ii != 0)
{
PORTB = frameBuffer[ii][position] | (PORTB & B00111100);
// Micro-correction
NOP;
NOP;
NOP;
NOP;
// Waste some time to make sure the line is sent during the proper timing
delayMicroseconds(lineDelay);
ii--;
}
/*
for (ii = 0; ii < _tvPixelWidth; ii++)
{
PORTB = frameBuffer[ii][position] | (PORTB & B00111100);
// Micro-correction
NOP;
NOP;
NOP;
NOP;
// Waste some time to make sure the line is sent during the proper timing
delayMicroseconds(lineDelay);
}
*/
}
/**
* Generate sync pulse for the virtual sync (lasts _tvVSyncNbrLines lines)
**/
void generateVSync(void)
{
unsigned char ii = _tvVSyncNbrLines;
while(ii != 0)
{
// Begin V Sync
PORTB = _BLACK | (PORTB & B00111100);
delayMicroseconds(_ntscDelayHSyncStart);
PORTB = _SYNC | (PORTB & B00111100);
// Micro-correction
NOP;
NOP;
delayMicroseconds(_ntscDelayVSync);
ii--;
}
}
/**
* End of the NTSC Specific block
**/
#endif
#if _tvMode == _PAL
/* Nada */
#endif
/**
* Clears the frame buffer (if mode is true it will fill it with a chess board pattern)
**/
void fillFrameBufferWith(byte _level)
{
unsigned char index, index2;
for (index2 = 0; index2 < _tvPixelHeight; index2++)
{
for (index = 0; index < _tvPixelWidth; index++)
{
frameBuffer[index][index2] = _level;
}
}
}
/**
* Fills the frame buffer with black
**/
void clearFrameBuffer(void)
{
fillFrameBufferWith(_BLACK);
}
/**
* Fills the frame buffer with white
**/
void fillWhiteFrameBuffer(void)
{
fillFrameBufferWith(_WHITE);
}
/**
* Fills the frame buffer with gray
**/
void fillGrayFrameBuffer(void)
{
fillFrameBufferWith(_GRAY);
}
/**
* Fills the frame buffer with a pattern
**/
void fillPatternFrameBuffer(void)
{
unsigned char index, index2;
for (index2 = 0; index2 < _tvPixelHeight; index2++)
{
for (index = 0; index < _tvPixelWidth; index++)
{
frameBuffer[index][index2] = (index + index2) % 3 + 1;
}
}
}
/**
* Fills the frame buffer with random values
**/
void fillRandomFrameBuffer(void)
{
unsigned char index, index2;
for (index2 = 0; index2 < _tvPixelHeight; index2++)
{
for (index = 0; index < _tvPixelWidth; index++)
{
frameBuffer[index][index2] = rand()%3 + 1;
}
}
}
/**
* Allows setting pixels independently
**/
void setPixel(byte x, byte y, byte val)
{
frameBuffer[x][y] = val;
}
/**
* Copies a sprite to the frameBuffer
**/
void loadSprite(byte* graphic)
{
if (memcpy(frameBuffer[0], graphic, (_tvPixelWidth * _tvPixelHeight)));
}
}}}
