Carlitos’ Contraptions

Hypothetical situation: Let’s suppose tomorrow is your friend’s birthday and you forgot to get him/her a present. Also, let’s assume you have no money whatsoever, all nearby stores are closed and he/she doesn’t like things that come from the garbage.

What to do?
(a) You don’t give him any present at all (second best option).
(b) You make a gift yourself (best option).
(c) You go into exile.

I chose “b”. Below, instruction on how to make a quick and nice puzzle.

Materials

• 19 big nails
• a piece of wood

Tools

• hammer
• sand paper
• sanding machine (particularly useful, but optional)
• glue
• drill
• jig saw

In order to build a nice puzzle that will…well puzzle your friend for a while, especially if he/she is an engineering student, do as follows:

1. Cut a large piece of wood that will become the main board
2. Cut a small block that will stand and the nail stand.
3. Glue them together so they look nice and the nail stand is not in the way
4. Drill holes of equal depth on the small wood block so 18 nails can stand separately in each hole
5. Plant a nail in the middle of the board and make sure it is nice and vertical.
6. If you have some printable labels you can print the game instruction and stick them on an empty spot on the wood board. Make sure you sand everything well before applying the labels.
7. It should look like the picture below.

Game Instructions: Put all 18 nails on the central nail. The resulting structure should be stable.
This means they should all be placed so that they only touch the central nail’s head and maybe each other.

Game Solution: You can find the puzzle solution here.

Now enjoy your new puzzle. _

Project

I polished up the code for my Arduino POV display and I think it is now ready to be shown to the world!

The source code for the POV display can be downloaded here.

The parameters in the code can be changed in order to display other images besides of the default arrows.

Data

The displayed image is stored in the data string. Each drawing is divided in frames (i.e. one frame for each letter of a word) and each frame is divided in columns. The image to be displayed must be encoded into 1s (ON) and 0s (OFF) and each value must be stored in the data string in the order illustrated below.

The duration of each column (i.e. how much time they stay ON), the spacing between frames and the spacing between images are set respectively by the integers timer1, timer2 and timer3. Keep in mind that their values depend on the rotation speed.

Finally, the number of frames and their length is set respectively by frame_num and frame_len.

Arrow (>):

• timer1: 3
• timer2: 15
• timer3: 0
• data: {1,0,0,0,0,1, 1,1,0,0,1,1, 0,1,1,1,1,0, 0,0,1,1,0,0}
• frame_len: 4
• frame_num: 1

“Alan” (my brother’s name):

• timer1: 3
• timer2: 15
• timer3: 13
• data: {1,1,1,1,1,1, 1,0,0,1,0,0, 1,0,0,1,0,0, 1,1,1,1,1,1, 1,1,1,1,1,1, 0,0,0,0,0,1, 0,0,0,0,0,1, 0,0,0,0,0,1, 1,1,1,1,1,1, 1,0,0,1,0,0, 1,0,0,1,0,0, 1,1,1,1,1,1, 1,1,1,1,1,1, 0,1,1,0,0,0, 0,0,0,1,1,0, 1,1,1,1,1,1}
• frame_len: 4
• frame_num: 4

Sinewave (or girly flower):

• timer1: 3
• timer2: 3
• timer3: 0
• data: {0,0,1,0,0,0, 0,1,0,0,0,0, 1,0,0,0,0,0, 1,0,0,0,0,0, 0,1,0,0,0,0, 0,0,1,0,0,0, 0,0,0,1,0,0, 0,0,0,0,1,0, 0,0,0,0,0,1, 0,0,0,0,0,1, 0,0,0,0,1,0, 0,0,0,1,0,0}
• frame_len: 12
• frame_num: 1

E = MC^2:

• timer1: 2
• timer2: 10
• timer3: 22
• data: {1,1,1,1,1,1, 1,0,0,1,0,1, 1,0,0,1,0,1, 1,0,0,1,0,1, 1,0,0,1,0,1, 0,0,0,1,0,1, 0,0,0,1,0,1, 0,0,0,1,0,1, 0,0,0,1,0,1, 0,0,0,1,0,1, 1,1,1,1,1,1, 0,1,0,0,0,0, 0,0,1,0,0,0, 0,1,0,0,0,0, 1,1,1,1,1,1, 0,1,1,1,1,0, 1,0,0,0,0,1, 1,0,0,0,0,1, 1,0,0,0,0,1, 0,1,0,0,1,0, 0,1,0,0,1,0, 1,0,0,1,1,0, 1,0,1,0,1,0, 0,1,0,0,1,0, 0,0,0,0,0,0}
• frame_len: 5
• frame_num: 5

Arduino, Project

This is my first attempt to create a persistence of vision (POV) display using the Arduino. The ultimate goal is to mount it on my bike wheel and have it display nice things while I ride. But, for now, it consist of an array of 6 LEDs mounted on a turning rig I made From scrap material.

Materials for the rig:

• 2 old cell phone batteries (found in the garbage) that serve as a counterweight
• A piece of metal (from an old photocopier) that constitutes the turning blade
• A fan motor from some sort of broken power supply I found in the UdeM garbage
• A piece of plastic that makes the base (also from the photocopier)
• A plastic poster edge (the things used to hold paper posters) that I found in the garbage (it is used to cover the sharp edges of the blade).
• A heavy metal block that stabilizes the contraption (since it tends to oscillate a bit when it’s turning)
• A cable with a switch from an IKEA lamp I found in the garbage
• Lots of cable ties

Materials for the POV circuit:

• A small breadboard (it came with an electronics magazine)
• 6 red high power LEDs
• 6 1 k Ohms resistors
• A 9V battery w/ battery older

I think the pictures are pretty self explanatory.

The LEDs are directly connected to the pins 2 to 7 of the Arduino and their current is limited by the resistors.
The entire circuit is powered by the 9V battery.

So far I have done some simple patterns for the display and I’ll upload the code soon (it still needs some polish)

I expect to add more LEDs to the design as soon as I get the patterns and the overall code working fine.

Arduino, Project

Recently my girlfriend got rid of her cable television connection and moved to a cheaper (almost free) and fully featured media center solution (i.e. Xbox + Xbox Media Center).
Meterials

• Xbox (not 360)
• Xbox remote (not required, but useful)
• Xbox Controller (usually comes with the Xbox)
• Xbox memory card (8 MB is enough)
• Modded Xbox from a relative (for a one time use)
• MechAssault game disk
• Softmod installer
• Computer, router, high speed internet connection, electricity (you should already have these).

General Idea
The idea is to unlock the Xbox, which is basically a very cheep computer, in order to run the very excellent and free Xbox Media Center (XBMC), a very advanced media player. Then, the Xbox can be use to watch videos, play music, stream content from the internet, and more (all in the comfort of the living room).

I know XBMC has been around for many years now, but I think is a good idea to write a post to show off its incredible features and explain how to get it.

How to do it
First, get all the materials. My girlfriend and I got a second hand Xbox complete with a remote and a controller for 100$ at Comptant.com after searching around a lot for a good deal. Then, I got a Mechassault original (not the platinum edition) game disk for 9$ and an 8MB memory card for 10$ (all second hand). So we spent a total of 120$ (much cheaper than any commercial media center).

In order to get the Xbox to run homebrew software (i.e. software that is not signed by Microsoft such as XBMC) its security system must be disabled. This can be done by installing a softmod (witch doesn’t require any hardware modification of the gaming system).

I choose to use the Krayzie Ndure SOFTMOD Pack that can be downloaded from the torrents. The idea is to get one of the game saves from this package (depending on which game you want to use) into the memory card and then into the Xbox. In order to get the MechAssault save to the memory card I used my own (hard)modded Xbox: I copied the game save folder to the E:\UDATA folder trough FTP and then I copied the game save (named Linux Installer) to the memory card by using the original Xbox dash. If you don’t have access to a modded Xbox, there are other ways of getting the save to the Xbox such as Action Replay or building a USB adapter.

Now, the easy part. Once you have the game save in the memory card, connect the Xbox to the router (as you would connect any other computer to it), plug the card into the controller, and turn the console on. Then, in the Xbox dash, go to the memory menu and copy the game save to the Xbox hard drive (hdd). Afterwards, insert the MechAssault disk, select the campaign menu entry, and then select “Linux Installer”. This will take you to a dashboard that will guide you through the installation of the softmod. Simply follow the steps (back up the eeprom and install the softmod) and in less than 2 minutes you will have a modded Xbox with your dashboard of choice (you can chose between EvolutionX or UnleashedX).

Now you can play game backups, run unsigned software and much more. Note that you need to update the Xbox dash to the latest version in order for the softmod installer to work properly. This can be done by using the “Live” menu entry in the Xbox dash.

Now that the Xbox is modded, you need to install XBMC. I used the latest Pimped version that comes with all the features you would want (codecs, scripts, visualizations, skins) and can be downloaded from the torrents. Once you have it downloaded and unziped, you must copy the XBMC folder to E:/apps in the Xbox’s hdd (the usual applications folder) through FTP (sending files trough FTP is the standard way of installing application onto the Xbox).

For FTP communication with the Xbox you can use any FTP client you want (I use Konqueror). In order to connect to the Xbox you need to know its IP address (which is normally shown on the main menu of the evolution dashboard) and its user name (Xbox) and password (Xbox). for further information in connecting to the Xbox trough FTP, please see this site.

Once the XBMC folder has been copied to E:/apps, reboot the Xbox (this will update the dashboard menu), and go to the applications menu an chose Xbox Media Center in order to start this wonderful program. You can also set it to start automatically (I recommend this) by following this guide.

Now that you have XBMC up , running and connected to the internet you can:

• play videos/music/pictures stored on any computer connected to router trough SMB (windows network) or stored in the local hd (it support almost all audio/video formats known to man).
• Play PAL and NTSC DVDs/VCDs from any region.
• Stream media from the internet, including tv shows, podcasts, movies, music, music videos, and much more.
• Check the weather forecast.
• And tons of other cool things.

Some Screenshots(note that the top and bottom black borders are not shown in the TV screen)

Final Remarks
Don’t forget to configure XBMC to adjust it to your needs (I recommend using the MC360 skin). For further information about using XBMC please consult the user’s manual.

You have now a very powerful media center that is far superior than any of the commercial alternatives I know. Enjoy.

Besides, you may also want to install some other great application such as dvd2xbox, which allows to backup entire games to the Xbox hdd, and boXplorer, an excellent file manager. You can get them from the usual places.

Project

My friends David and Kanwen, and I implemented a speech recognition system on an FPGA development board (Altera DE2 Board) for the Design Project course at McGill (ECSE 494). We did this in two step: first we wrote a prototype for the algorithm in MATLAB (I’ll maybe port it to Octave), and then we did the hardware description for the FPGA.

MATLAB Prototype

Inspired by the algorithm described in a site from the University of Toronto, we wrote two MATLAB scripts: train.m and recogniz.m.

train.m deals with the training phase, in which many versions of a sound (a spoken word for instance) are input and averaged in the frequency domain thus generating the sound’s “reference fingerprint”.

recogniz.m deals with the recognition phase, where a sound is input, translated to the frequency domain (i.e. Its fingerprint is generated), and compared to the reference fingerprint by computing the euclidean distance between them (as if both fingerprints where vectors).

Both scripts need to detect the beginning of the sound (i.e tell when the spoken word begins). They do so by averaging two adjacent 1024-sound-samples groups (in the time domains) and computing the difference between the averages. So, if there is a sudden increase in the sound’s amplitude, the difference will be significant and the sound is assumed to start after that sudden increase. The sound’s length is fixed to 1,024 s (see the picture below for more details)

Note that the scripts use 16-bit WAV files as input @ 22050 Hz (this is the default windows sound recorder output, since I could not do it in Linux because the mic did not wanted to work). The sound input is downsampled and quantized in order to get it down to 8 bit /sample @ 5 kHz for processing.

Also you might encounter problems if the sound file is too short (it should last for more than 1,1 s), or if its volume level is too low (this happens because the detector threshold is fixed).

Hardware Implementation

Once we had played enough with the MATLAB prototype parameters, we mapped the algorithm into combinational logic and finite state machines (FSM) by breaking it down into independent modules.

For more details about the hardware implementation and the project in general you can read the full project report. You may also want to see the slides for a presentation we did (below).

Unfortunately, I cannot post the project files (i.e. VHDL code).

Here is a little video demo, enjoy:

Note that all the documentation for this project was done using the very excellent OpenOffice.org.

FPGA, Project