Download the code directly here: LED_Matrix_TTT4.pde

Some general notes:

1. The AI is based on game theory taken from a book I read about 20 years ago. Unfortunately I don’t remember the name of it. It uses a Minimax algorithm as well as Alpha-beta pruning to decrease the number of nodes that need to be evaluated. Wikipedia offers a concise description of these with many external links. I spent about a month learning the algorithms and coding them, so I’m sure they can be greatly enhanced, especially since more than 20 years has past. However, I am proud to say that pitting this program up against another 3D TTT I found online, that mine trounced the other.

2. I wanted the LED matrix cube to be constantly displaying the player LED spot selection, the current cube moves, or the computer thinking (LEDs going on and off). In order to do this, even while the Arduino is off doing other things, I needed to use interrupts.  Using the MsTimer2 library I was able to set up a routine, disp_LED_cube, that was called every 200 ms with 1 of 4 states:

• state 0: Default display of all moves
• state 1: setting up player’s move
• state 3: blinking last computer move
• state 4: computer “thinking”

3. The current program uses a keypad to make the moves. The keys 1-4 are for selection of the player’s move. It first uses a ‘wall’ to select the z-direction, with the keys moving the wall. After the proper wall is selected, the ’5′ key will then lock-in that wall, and display a column that represents the y-direction. Again, the 1-4 keys allow for the selection of the wished-upon column. Player then pushes ’5′ key to lock-in column. Finally, user selects for the specific LED in column they wish to use as their move. Pressing the ’5′ key will begin the Arduino deciding its move. I’m currently working on code to use a thumbstick rather than the keypad.

4. The code is GPL. Please use it as you like and definitely improve upon it. I would, of course, really like you to credit me for the work I’ve put into it should you use it.

Here is the code:

/*

	LED_Matrix_TTT4.C - An AI version of Tic-Tac-Toe, played on a 4x4x4 LED matrix
        powered by an Arduino

    Copyright (C) 2011  Jeffrey R. Gilmour, Ph.D.

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#include <Sprite.h>
#include <Matrix.h>
#include <MsTimer2.h>	// Uses pins 3 & 11, so DON'T USE those

const int loadPin = 4;
const int clockPin = 5;
const int dataPin = 6;

Matrix myMatrix = Matrix(dataPin, clockPin, loadPin);

#define FALSE 0
#define TRUE !FALSE
boolean OLedsOn = TRUE;

char cube0[4][4][4], cube1[4][4][4], cube2[4][4][4], cube3[4][4][4], human_symbol='X', comp_symbol='O';

const int period = 200;

const int numRows = 2;
const int rowPins[numRows] = { 7, 8 };		// Keypad pins 1 & 2, attached to Arduino pins 7 & 8

const int numCols = 3;
const int colPins[numCols] = { 9, 10, 12 };	// Keypad pins 5, 6 & 7

const int debounceTime = 200;

const char keymap[numRows][numCols] = {		// USE PINS 1, 2, 5, 6, 7 on keypad
	{ '1', '2', '3' },
	{ '4', '5', '6' }
};

char key = 0;

int state = 0, state1x = 5, state1y = 5, state1z = 5;
int	bestmovex, bestmovey, bestmovez;

char getKey() {
	key = 0;	

	for (int column = 0; column < numCols; column++) {
		digitalWrite(colPins[column], LOW);
		for (int row = 0; row < numRows; row++) {
			if(digitalRead(rowPins[row]) == LOW) {
				delay(debounceTime);
				while(digitalRead(rowPins[row]) == LOW) ;
				key = keymap[row][column];
			}
		}
		digitalWrite(colPins[column], HIGH);
	}

	return key;
}

char check(char board[4][4]) {

	int i;

	for (i=0;i<4;i++)		/* check rows */
		if (board[i][0]==board[i][1] &&
		   board[i][0]==board[i][2] &&
		   board[i][0]==board[i][3]) if (board[i][0]!=' ')
		   	return board[i][1];

	for (i=1;i<=4;i++)		/* check columns */
		if (board[0][i]==board[1][i] &&
		   board[0][i]==board[2][i] &&
		   board[0][i]==board[3][i]) if (board[0][i]!=' ')
		   	return board[1][i];

	/* test diagonals */
	if (board[0][0]==board[1][1] && board[1][1]==board[2][2] &&
	   board[2][2]==board[3][3] && board[0][0]!=' ')
		return board[1][1];

	if (board[0][3]==board[1][2] && board[1][2]==board[2][1] &&
	   board[2][1]==board[3][0] && board[0][3]!=' ')
		 return board[1][2];

	return ' ';
}

void disp_LED_cube(void) {

	if (state == 0) {		// Default display of all moves
		for (int z=0;z<4;z++)
			for (int y=0;y<4;y++)
				for (int x=0;x<4;x++) {
					if (OLedsOn) {
						if (cube0[x][y][z] == 'O') {
							if (z == 0) {
								myMatrix.write(y, x, LOW);
							} else if (z == 1) {
								myMatrix.write(y, x+4, LOW);
							} else if (z == 2) {
								myMatrix.write(y+4, x+4, LOW);
							} else if (z == 3) {
								myMatrix.write(y+4, x, LOW);
							}
						}
					} else {
						if (cube0[x][y][z] != ' ') {
							if (z == 0) {
								myMatrix.write(y, x, HIGH);
							} else if (z == 1) {
								myMatrix.write(y, x+4, HIGH);
							} else if (z == 2) {
								myMatrix.write(y+4, x+4, HIGH);
							} else if (z == 3) {
								myMatrix.write(y+4, x, HIGH);
							}
						}
					}
				}
		OLedsOn = !OLedsOn;
	}

	if (state == 1) {	// setting up player's move
		myMatrix.clear();
		if (state1z < 5) {

						if (state1z == 0) {
							myMatrix.write(state1y, state1x, HIGH);
						} else if (state1z == 1) {
							myMatrix.write(state1y, state1x+4, HIGH);
						} else if (state1z == 2) {
							myMatrix.write(state1y+4, state1x+4, HIGH);
						} else if (state1z == 3) {
							myMatrix.write(state1y+4, state1x, HIGH);
						}

		} else
		if (state1y < 5) {
				for (int z=0;z<4;z++)
						if (z == 0) {
							myMatrix.write(state1y, state1x, HIGH);
						} else if (z == 1) {
							myMatrix.write(state1y, state1x+4, HIGH);
						} else if (z == 2) {
							myMatrix.write(state1y+4, state1x+4, HIGH);
						} else if (z == 3) {
							myMatrix.write(state1y+4, state1x, HIGH);
						}
		} else
		if (state1x < 5) {
				for (int z=0;z<4;z++)
					for (int y=0;y<4;y++) {
						if (z == 0) {
							myMatrix.write(y, state1x, HIGH);
						} else if (z == 1) {
							myMatrix.write(y, state1x+4, HIGH);
						} else if (z == 2) {
							myMatrix.write(y+4, state1x+4, HIGH);
						} else if (z == 3) {
							myMatrix.write(y+4, state1x, HIGH);
						}
					}
		}
	}

	if (state == 3) {		// blinking last computer move

		if (OLedsOn) {
			if (bestmovez == 0) {
				myMatrix.write(bestmovey, bestmovex, LOW);
			} else if (bestmovez == 1) {
				myMatrix.write(bestmovey, bestmovex+4, LOW);
			} else if (bestmovez == 2) {
				myMatrix.write(bestmovey+4, bestmovex+4, LOW);
			} else if (bestmovez == 3) {
				myMatrix.write(bestmovey+4, bestmovex, LOW);
			}
		} else {
			if (bestmovez == 0) {
				myMatrix.write(bestmovey, bestmovex, HIGH);
			} else if (bestmovez == 1) {
				myMatrix.write(bestmovey, bestmovex+4, HIGH);
			} else if (bestmovez == 2) {
				myMatrix.write(bestmovey+4, bestmovex+4, HIGH);
			} else if (bestmovez == 3) {
				myMatrix.write(bestmovey+4, bestmovex, HIGH);
			}
		}
		OLedsOn = !OLedsOn;
	}

	if (state == 4) {		// computer "thinking"
		myMatrix.clear();
		for (int z=0;z<4;z++)
			for (int y=0;y<4;y++)
				for (int x=0;x<4;x++) {
					if (OLedsOn) {
						if (cube3[x][y][z] == 'O') {
							if (z == 0) {
								myMatrix.write(y, x, LOW);
							} else if (z == 1) {
								myMatrix.write(y, x+4, LOW);
							} else if (z == 2) {
								myMatrix.write(y+4, x+4, LOW);
							} else if (z == 3) {
								myMatrix.write(y+4, x, LOW);
							}
						}
					} else {
						if (cube3[x][y][z] != ' ') {
							if (z == 0) {
								myMatrix.write(y, x, HIGH);
							} else if (z == 1) {
								myMatrix.write(y, x+4, HIGH);
							} else if (z == 2) {
								myMatrix.write(y+4, x+4, HIGH);
							} else if (z == 3) {
								myMatrix.write(y+4, x, HIGH);
							}
						}
					}
				}
		OLedsOn = !OLedsOn;
	}

}

char check_cube(char cube[4][4][4]) {

	int x, y, z, n=0;
	char done, board[4][4];

	for (z=0;z<4;z++) {	/* boards in Z direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[x][y][z];
		done=check(board);
		if (done!=' ') return done;
	}

	for (z=0;z<4;z++) {	/* boards in Y direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[x][z][y];
		done=check(board);
		if (done!=' ') return done;
	}

	for (z=0;z<4;z++) {	/* boards in X direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[z][y][x];
		done=check(board);
		if (done!=' ') return done;
	}

	/* 3D diagonal 1 */
	if (cube[0][0][0]==cube[1][1][1] && cube[0][0][0]==cube[2][2][2]
		&& cube[0][0][0]==cube[3][3][3] && cube[0][0][0]!=' ')
		return cube[0][0][0];

	/* 3D diagonal 2 */
	if (cube[0][0][3]==cube[1][1][2] && cube[0][0][3]==cube[2][2][1]
		&& cube[0][0][3]==cube[3][3][0] && cube[0][0][3]!=' ')
		return cube[0][0][3];

	/* 3D diagonal 3 */
	if (cube[3][0][0]==cube[2][1][1] && cube[3][0][0]==cube[1][2][2]
		&& cube[3][0][0]==cube[0][3][3] && cube[3][0][0]!=' ')
		return cube[3][0][0];

	/* 3D diagonal 4 */
	if (cube[0][3][0]==cube[1][2][1] && cube[0][3][0]==cube[2][1][2]
		&& cube[0][3][0]==cube[3][0][3] && cube[0][3][0]!=' ')
		return cube[0][3][0];

	for (z=0;z<4;z++)	/* if no spaces are empty, game is a draw */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				if (cube[x][y][z]==' ') n++;
	if (n==0) {
		// Game is a draw - how to communicate to player?
		loop();
	}

	return done;
}

void copy_cube(char b2[4][4][4], char b1[4][4][4]) {

	int x,y,z;

	for (z=0;z<4;z++)
		for (y=0;y<4;y++)
			for (x=0;x<4;x++) b2[x][y][z]=b1[x][y][z];

}

void get_computer_move(void) {

	long int	s0=-100000, s1, s2;
	int		test=0, x1, y1, z1, x2, y2, z2, x3, y3, z3, NoGood, NoGood2;
	int		score;
	char	done;

	state = 4;		// computer "thinking" LED display

	for (z1=0;z1<4;z1++)
	    for (y1=0;y1<4;y1++)
		for (x1=0;x1<4;x1++) {

		    s1=100000;
		    NoGood=FALSE;

		    if (cube0[x1][y1][z1]==' ') {
			copy_cube(cube1,cube0);
			cube1[x1][y1][z1]=comp_symbol;

			done = check_cube(cube1);	// Computer has WON!
			if (done==comp_symbol) {
				bestmovex = x1;
				bestmovey = y1;
				bestmovez = z1;

				state = 3;		// blinking last move of computer
				while (getKey() == 0) ;
				state = 0;

				copy_cube(cube0,cube1);

				while (getKey() == 0) ;
				loop();

			}

			for (z2=0;z2<4 && !NoGood;z2++)
			    for (y2=0;y2<4 && !NoGood;y2++)
					for (x2=0;x2<4 && !NoGood;x2++) {

				    	s2=-100000;
				    	NoGood2=FALSE;

					    if (cube1[x2][y2][z2]==' ') {
							copy_cube(cube2,cube1);
							cube2[x2][y2][z2]=human_symbol;

							for (z3=0;z3<4 && !NoGood2;z3++)
							    for (y3=0;y3<4 && !NoGood2;y3++)
									for (x3=0;x3<4 && !NoGood2;x3++) {
								    	if (cube2[x3][y3][z3]==' '){
											copy_cube(cube3,cube2);
											cube3[x3][y3][z3]=comp_symbol;
							   	 			score=score_cube(cube3);
											if (s2<score) {
										    	s2=score;
										    	if (s2>s1) NoGood2=TRUE;
											}
								    	}
									}
					   		if (s1>s2) {
					   		   	s1=s2;
					   		   	if (s1<s0) NoGood=TRUE;
							}
					    }
			}

			if (s0<s1) {
			    s0=s1;
			    bestmovex=x1;
			    bestmovey=y1;
			    bestmovez=z1;
			}
		    }
		}

	cube0[bestmovex][bestmovey][bestmovez]=comp_symbol;

	myMatrix.clear();
	state = 3;					// blinking last move of computer
	while (getKey() == 0) ;		// wait until player has pressed a button, then display regular cube
	state = 0;
}

int score_cube(char cube[4][4][4]) {

	int scores=0, x, y, z, tally_comp=0, tally_human=0;
	int comp[5]={0,0,0,0,0}, human[5]={0,0,0,0,0};
	char board[4][4];

	for (z=0;z<4;z++) {	/* boards in Z direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[x][y][z];
		scores+=score(board);
	}

	for (z=0;z<4;z++) {	/* boards in Y direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[x][z][y];
		scores+=score(board);
	}

	for (z=0;z<4;z++) {	/* boards in X direction */
		for (y=0;y<4;y++)
			for (x=0;x<4;x++)
				board[x][y]=cube[z][y][x];
		scores+=score(board);
	}

	for (z=0;z<4;z++) {	/* 3D diagonal 1 */
		tally_comp+=(cube[z][z][z]==comp_symbol);
		tally_human+=(cube[z][z][z]==human_symbol);
	}

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	tally_comp=0;
	tally_human=0;

	for (z=0;z<4;z++) {	/* 3D diagonal 2 */
		tally_comp+=(cube[3-z][z][z]==comp_symbol);
		tally_human+=(cube[3-z][z][z]==human_symbol);
	}

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	tally_comp=0;
	tally_human=0;

	for (z=0;z<4;z++) {	/* 3D diagonal 3 */
		tally_comp+=(cube[z][3-z][z]==comp_symbol);
		tally_human+=(cube[z][3-z][z]==human_symbol);
	}

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	tally_comp=0;
	tally_human=0;

	for (z=0;z<4;z++) {	/* 3D diagonal 4 */
		tally_comp+=(cube[z][z][3-z]==comp_symbol);
		tally_human+=(cube[z][z][3-z]==human_symbol);
	}	

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	scores+=comp[1]-3*human[1]+7*comp[2]-15*human[2]+31*comp[3]-63*human[3]+127*comp[4]-1000*human[4];
	return scores;

}

int score(char board[4][4]) {

	int x, y, tally_comp=0, tally_human=0, comp[5]={0,0,0,0,0}, human[5]={0,0,0,0,0};

	for (y=0;y<4;y++) {						/* Rows */
		for (x=0;x<4;x++) {
			tally_comp+=(board[x][y]==comp_symbol);
			tally_human+=(board[x][y]==human_symbol);
		}

		if (tally_comp>0 && tally_human>0) {
			tally_comp=0;
			tally_human=0;
		}

		comp[tally_comp]++;
		human[tally_human]++;

		tally_comp=0;
		tally_human=0;
	}

	for (x=0;x<4;x++) {						/* Columns */
		for (y=0;y<4;y++) {
			tally_comp+=(board[x][y]==comp_symbol);
			tally_human+=(board[x][y]==human_symbol);
		}

		if (tally_comp>0 && tally_human>0) {
			tally_comp=0;
			tally_human=0;
		}

		comp[tally_comp]++;
		human[tally_human]++;

		tally_comp=0;
		tally_human=0;
	}

	for (y=0;y<4;y++) {						/* Down diagonal */
		tally_comp+=(board[y][y]==comp_symbol);
		tally_human+=(board[y][y]==human_symbol);
	}

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	tally_comp=0;
	tally_human=0;

	for (y=0;y<4;y++) {						/* Up diagonal */
		tally_comp+=(board[3-y][y]==comp_symbol);
		tally_human+=(board[3-y][y]==human_symbol);
	}

	if (tally_comp>0 && tally_human>0) {
		tally_comp=0;
		tally_human=0;
	}

	comp[tally_comp]++;
	human[tally_human]++;

	y=comp[1]-3*human[1]+7*comp[2]-15*human[2]+31*comp[3]-63*human[3]+127*comp[4]-1000*human[4];
	/* Needs to be the same evaluation function as in 'score_cube' function */
	return y;

}

void init_cube (void) {

	int x,y,z;

	for(z=0;z<4;z++)
		for(y=0;y<4;y++)
			for(x=0;x<4;x++) cube0[x][y][z]=' ';
}

void get_player_move(void) {

	int x,y,z;

	while (getKey() == 0) ;

	state = 1;
	state1x = 5;
	state1y = 5;
	state1z = 5;

	do {
		while (getKey() == 0) ;
		if (key < '5')
			state1x = (key - '0') - 1;
	} while (key != '5' || state1x > 3 );
	x = state1x;

	do {
		while (getKey() == 0) ;
		if (key < '5')
			state1y = (key - '0') - 1;
	} while (key != '5' || state1y > 3 );
	y = state1y;

	do {
		while (getKey() == 0) ;
		if (key < '5')
			state1z = (key - '0') - 1;
	} while (key != '5' || state1z > 3 );
	z = state1z;

	if (cube0[x][y][z]!=' ') {			// Invalid move - redo entry
		get_player_move();
	}

	cube0[x][y][z]=human_symbol;
	state = 0;
}

void setup() {

	for (int row = 0; row < numRows; row++) {
		pinMode(rowPins[row], INPUT);
		digitalWrite(rowPins[row], HIGH);
	}
	for (int column = 0; column < numCols; column++) {
		pinMode(colPins[column], OUTPUT);
		digitalWrite(colPins[column], HIGH);
	}
}

void loop() {
	char done, Buf[12];
	int x,y,z;

	state = 1;	// Pre-game cube LED flashing
	done = ' ';

	myMatrix.clear();

	init_cube();
	MsTimer2::set(period, disp_LED_cube);
	MsTimer2::start();

	while (getKey() == 0) ;			// Press 1 to go first
	state = 0;		// Normal display of cube LED
	if (key != '1') {
		human_symbol='O';
		comp_symbol='X';
		get_computer_move();
	}

	do {
		state = 0;
		get_player_move();
		done=check_cube(cube0);
		if (done != ' ') break;
		get_computer_move();
		done=check_cube(cube0);
	} while (done==' ');

	if (done==human_symbol) ;			// Player has WON!
	else ;						// Compute has WON!

}

As always, if you have any questions, need further assistance or require additional pictures or diagrams, please let me know in the comments and I’ll do my best to address them.

Up Next: Figuring Out How To Select Player Moves (determining pin combinations for particular keys on an unknown keypad, and hard coding)

As you’ve probably heard, the Revo gives you more than your usual money’s worth by including an onboard Nvidia Ion graphics chip. The Nvidia engineers have very kindly released drivers which allow the graphics chip to do the video decoding rather than bogging down the rather slow Intel Atom 230 CPU with the chore. This results in only ~20% CPU utilization with near flawless playback of HD videos, instead of 100% CPU overload and very choppy video. A $200 computer that can do this is a very good deal.

I recommend a full install of Ubuntu Karmic 9.10. Other sites have instructions for installing a “minimal” gnome setup. I think this is silly. It strips the system of a host of useful applications, while providing non-discernible “improvements”. With the normal full installation of Ubuntu not only will you be able to play video and audio (movies and music) files, but should you choose, also browse the Internet, do email, perform normal office tasks (word processing, spreadsheets, presentations) and more. Provided, the Acer Revo is not a powerhouse and I wouldn’t recommend it for editing photos or videos.

Note that I am NOT an expert on any of this. I’ve been an avid Linux user since Linus announced it back in 1991, but XBMC, the Revo, and the VDPAU driver are all relatively new to me. I will attempt to provide appropriate links for more information on all of these. In fact, all of the information here has been gleamed from numerous websites and postings from other generous XBMC users. I’ll try and note that as possible. Also, I’m assuming at least some competency with a Linux system. If there are an questions feel free to ask them in the comments section.  Read this entire article, including the notes at the end, before attempting.

Reference System and Hardware: this is a list of my setup and all of the equipment I used that was necessary to make it work. Of course, other equipment will likely work, but this is what I used.

• Acer Aspire Revo 1600, model #AR1600-U910H
• Patriot 2 GB PC2-8400 800 MHz CL6 Memory, model #PSD22G8002S (swapped with installed 1 GB module)
• Samsung 40″ LCD TV, model #LN40A550 (1920×1080, HDMI)
• 2 meter HDMI cable (don’t pay more than $10 or you’re being ripped off)
• 2 GB USB flashdrive
• MCE remote, model #GP-IR02BK

INSTALLING UBUNTU KARMIC 9.10 ON THE ACER ASPIRE REVO

The Acer Revo doesn’t have an optical drive, so the OS will need to be installed via an USB optical drive or a USB flashdrive. I recommend a USB flashdrive installation and that’s what I’ll describe here.

1. Download the Ubuntu Karmic 9.10 iso image from ubuntu.com.
2. Download Unetbootin from unetbootin.sourceforge.net and install it.
3. Insert a FAT formatted >2 GB flash drive into the computer. Note that FAT is already the default filesystem for most flash drives. Run Unetbootin, select Diskimage and tell it where to find the iso image file you downloaded. Next to “Type” USB Drive should be automatically chosen.  Next to “Drive” select either the letter of the USB flash drive (for Windows) or the correct device (i.e. /dev/sdb1 for Linux).  Hit “OK” to set up the flash drive as a Ubuntu installation drive.  When it’s finished hit “Exit”, remove the USB flashdrive and insert it into your smokin’ Acer Aspire Revo!The model of Revo that I have had Windows XP pre-installed. I decided to keep a 30 GB drive partition with the XP still on it, so I’ll explain how I did that.  I’ll assume you’ve already hooked the Revo up with the mouse, keyboard and an appropriate display. Hopefully, the display is connected via an HDMI cable.  Also it’s advantageous to have it attached to your router either through ethernet or USB wireless – during installation it will set the computer clock and download additional content.
4. Turn on the Revo and hit DELETE when the display suggests it. Under “Advanced BIOS Features” select “Hard Disk Drive Priority” and change the USB flashdrive to the top position. Hit F10 to save and exit. Select “Default” from the Unetbootin menu that comes up, and the computer should boot into Ubuntu Live ready for installation.
5. Double click on the Installation icon.  Just follow the simple on screen instructions until you get to the partition page.  At this point, if you want to keep the original M$ Windows installation, select the bottom option, click on the Windows bar and slide it to indicate how large you want to keep that partition.  Again, I selected 30 GB which would allow me to install and occasionally play M$ Windows games. (I highly recommend Torchlight – a Diablo clone – it’s gorgeous, fun, works well on the Revo, and is just $20, downloadable from Direct2Drive.) Otherwise, if you just want a simple Ubuntu system select the top option. Continue following the simple on screen instructions. On the “Who are you?” page I selected “Log in automatically”. Installation should take less than 30 minutes. Reboot minus the flashdrive.

Congratulations! You’ve got a full Ubuntu Karmic operating system.

INSTALLING THE LATEST NVIDIA VIDEO DRIVERS

1. First update standard Ubuntu. Open up a terminal window and bring Ubuntu completely up to date with the following commands:
   

   sudo apt-get update
   sudo apt-get upgrade [Note: hold off on reboot]
   sudo apt-get dist-upgrade [Note: hold off on reboot]

   It may take a while to download and install all the latest updates. Note that throughout the rest of this installation the system may pop up boxes asking you to reboot, update or install a graphics driver. You can safely close and ignore them.

2. Now it’s time to grab the latest drivers for the Nvidia Ion graphics chip. From the terminal window run:
   

   sudo add-apt-repository ppa:nvidia-vdpau/ppa
   sudo apt-get update [Note: DO NOT upgrade]
   sudo apt-get install nvidia-glx-195 nvidia-195-modaliases

3. Reboot the machine.
4. The drivers aren’t installed yet. From the upper task bar select System -> Administration -> Hardware Drivers. Select “NVIDIA accelerated graphics driver (version 195) [Recommended]”.  Click on the “Activate” button, and then the “Close” button.
5. Reboot again.
6. Finally, again from the upper task bar select System -> Administration -> Synaptic Package Manager. Search for “libvdpau1” and make sure it’s installed.

SELECT THE HDMI AUDIO DRIVER

By default, Ubuntu uses the standard audio ports for output. In order to get sound from your HDMI-attached TV do the following:

Right-click on the Sound icon in the upper panel. Select “Sound Preferences” and then the Hardware tab. From the Profile menu select “Digital Stereo (HDMI) Output”. Click the “Close” button. That’s it – you’ve got TV sound.

INSTALL XBMC

Installation couldn’t be much easier. From the terminal run:

sudo add-apt-repository ppa:team-xbmc
sudo apt-get update
sudo apt-get install xbmc
sudo apt-get update

You’ll now find XBMC from Applications -> Sound & Video -> XBMC Media Center

Everything should be working. To verify that your Nvidia chip is doing the decoding, hit “o” while running a video. The second line from the top should include something similar to “dc:ff-h264_vdpau”.

For more help on all things XBMC, visit their official website at http://xbmc.org , the Wiki at http://xbmc.org/wiki/?title=XBMC_Online_Manual, and the XBMC forums at http://xbmc.org/forum

BTW, I highly recommend the Aeon theme. It really shines on HDTV.

ADDITIONAL INFORMATION

I also purchased an MCE remote (Mediagate model #GP-IR02BK). This is an infrared remote control designed for controlling a media center. It makes the whole Revo/XBMC feel like an actual appliance since you won’t be using the keyboard and mouse much afterwards. I believe practically any MCE remote will work. Along with the remote you also get an IR receiver that plugs into a USB port. To get mine working I had to install the drivers with “sudo apt-get install lirc”. After that the remote magically controlled XBMC.

Like I noted in the parts section, I swapped out the computer’s initial 1 GB memory card for a 2 GB memory card.  I also increased the shared video memory from 256 KB to 512 KB in BIOS.  There are some reports that 2 GB and 512 KB shared is necessary to get properly working VPDAU.  I have not verified this as I installed the 2 GB before installing Ubuntu.  I’d like to hear if anyone has problems.

[NOTE: Added on February 2, 2010]

I just realized that since I swapped out the original 1 GB memory module for a new 2 GB module, that the 1 GB module is just sitting around on my desk unused.  So, if anyone’s interested in using it to upgrade their system to 2 GB, I’ll give it to the first person to request it in the comments.