As I managed to make the Arduino software work under linux, I did this week Make weekend project : “Intro to the Arduino”.

It’s really simple. When you push a button connected to pin 2, a led connected on pin 9 will fade in and out.
Easy isn’t it? Unfortunately I’m pretty bad in electronic. My first try made the led blink nervously. After several unsuccessful attempts, I decided to make things work step by step.

  1. The breadboard
    How does this thing work? After looking at this tutorial, it appears that my breadboard is separated by the center gap in 2 independent parts. Each part has 16 rows and 5 columns of contacts. All the contacts of a row are connected together.
  2. The led
    I put the led on the breadboard and connected it on pin 9. I tested it with the blinking led example. As always it didn’t work on the firsts attempt. The led was connected the wrong way.
  3. The button
    I spent a lot of time on it. I first have to figure out how it was working. So I modified the previous setup and put the button between the pin and the led. Once I got it working, I connected it to pin 2. Then according to the original schematic, I had to connect the rest of the circuit to the power pins.

Ten minutes later it was finally working! Here’s a totally wonderful and awesome video (edited with Avidemux) to prove it 🙂

[flashvideo filename=wp-content/uploads/2008/04/arduino01.flv /]

The road will be long and hard before I get the backup thingie for pc-engine done…


Months ago, I bought an Arduino. It comes with a nice ide but I always used it under Windows. This summer I decided to stop using Windows and I haven’t played with the Arduino since then.

Some days ago I purchased some stuffs from Sparkfun (some dataflash, resistors, etc…) in order to make some kind of backup device for the pc-engine. So I decided to install the Arduino softwares on my box. I’m currently running a Fedora core 7 for amd64. There are instructions for Fedora core 6 on Arduino site. But as I’m running on an amd64 I had to recompile some stuffs.

  1. Java
    There’s no official package for sun’s java on Fedora. Just follow the instructions from Jan K. Labanowski of the Computational Chemistry List, Ltd and you are done in less than 10 minutes.
  2. AVR tools
    It’s the easiest part. Fedora core 7 includes all you need. You’ll have to install the following packages:

    • avr-binutils.x86_64
    • avr-gcc.x86_64
    • avr-libc.noarch
    • avr-gcc-c++.x86_64
    • avr-libc-docs.noarch
    • avr-gdb.x86_64
    • avrdude.x86_64
  3. RXTX
    Arduino comes with a precompiled version of RXTX. Unfortunately it’s a 32bits version. You’ll have to recompile it or you’ll have some nasty messages when trying to run Arduino. Well, it won’t crash immediately. You’ll be able to set the program directory. But once you press OK, it will crash and you’ll get a nice error message.
    After trying to compile the CVS version of RXTX, I went for a release vesion. The latest one is 2.1-7r2. According to the INSTALL file, all I had to do was the standard “./configure; make; make install” combo.

    Unfortunatelly, the kernel headers test from the configure script failed. It’s trying to compile some piece of C code but. Here’s the error : error: 'UTS_RELEASE' undeclared (first use in this function) It seems that all distros are patching RXTX to remove the use of this variable. In fact it’s only used for a sanity check. If the current kernel version is different from the one RXTX was compiled for it will prompt some error message. If you really want to use it you’ll have to add the right header in the configure script (check_kernel_headers) and some various C files.

    I went the dirty way and simply removed it. Hopefully there’s a patch from the nslu2-linux project which will do the work for you on the sources. But you’ll still have to remove the check_kernel_headers() from the configure script.

    But that’s not the end of your problems! make install won’t work. You’ll have the following error :
    make all-am
    make[1]: Entering directory `//rxtx-2.1-7r2'
    make[1]: Nothing to be done for `all-am'.
    make[1]: Leaving directory `//rxtx-2.1-7r2'
    libtool: install: `x86_64-unknown-linux-gnu/' is not a directory
    Try `libtool --help --mode=install' for more information.
    make: *** [install] Error 1

    Hopefully this issue is addressed in the RXTX faq.

    After installing RXTX, edit /usr/java/jdk1.6.0_02/jre/lib/ (create the file if it’s missing) and add the following line :

    We are now ready to run the Arduino software!

  4. Arduino
    The latest version is Arduino 0009. Install it wherever you want. Let’s say ~/arduino. When you are done go to ~/arduino/lib. Remove RXTXcomm.jar and Then edit ~/arduino/arduino and modify both CLASSPATH and LD_LIBRARY_PATH to point to the directory containing RXTXcomm.jar and Here’s what it looks like on my system :


    At this point we are nearly done. Don’t forget to give your user the permission to the usb device (/dev/ttyUSB0 in my case). Plug the Arduino board and launch the ide. There’ll be some gcc warnings. Don’t pay attention to them.

    First set the serial port. Go to Tool > Serial Port and choose the correct interface. If you don’t know it, leave the menu and unplug the board. Go to the Serial Port menu and note the currently listed interface. Replug the board. And return to the Serial Port menu. A new usb interface may have appeared. It’s the interface the board is connected to.

    You’ll have to check if the ide is set to the microcontroller. If it’s not the case when you’ll want to upload your code to board, you’ll have the following error:
    avrdude: Expected signature for ATMEGA168 is 1E 94 06
    Take your board and look for the chip type. You can’t miss it, it’s written on it 🙂 To change the microcontroller go to Tools > Microcontroller (MCU) and choose your chip (ther’s an ATMEGA8 on my board).

    At this point everything should be alright.

8bitranger! Tornado blast!

Some months (nearly a year) ago, i made a post about etripator. It’s a pc-engine rom disassembler… At that time the code was pretty ugly. Except the csv file reading and other utility functions, all the work was made in a single C file and (worst of all) in the main function. Well some people started to test it and asked for new features.
You can easily imagine that as soon as i added new features, the all code became a real mess. If i didn’t want it to become unmaintainable and buggy as hell, i had to clean it up and start thinking seriously about its design. That’s what i did during my summer vacation. After a week of mad coding and testing, what first started as a toy looks more like a real usable program now.

Ladies and gentlemen! I’m pleased to announce the first official release of etripator!

The previous test releases can be found here.

I would like to thank tomaitheous, Charles MacDonald, B.T Garner, David Shadoff, all the punks on #utopiasoft and necstasy.

Expect more releases. Mainly because it was not heavily tested and it needs some polishing (especially the documentation. The ReadMe file I wrote sucks.).

Zero right ahead!

Yes! Zero wouldn’t be considered as the default/standard return error value. I learnt the hard way today.

I had some kind of weird NULL pointer bug. After some investigations, i found that the deserialization function was failing at some point leaving the whole structure uninitialized. First i blamed myself for not calling the standard structure initialization function when the deserialization function failed. Then i looked at the data file.
Everything seemed to be ok. So i went on a step by step execution with the debugger. 5 minutes later i found the culprit. It was zlib in the kitchen with ten tone hammer. It was strange.

Let’s say that i compressed a buffer of N bytes into M bytes. When i read back the N bytes from the compressed buffer, i get the whole data before the end of the compressed buffer. Leaving me with 5 extra bytes.
On the next run i try to read P bytes. But i still have those 5 bytes to decompress. So i feed them to inflate (the zlib decompression routine). It returns a nice Z_STREAM_END. At this point, nothing wrong as i finished to process the previous compressed buffer. But (and that’s a big but     …     sorry    ) no bytes were output.
In fact it’s an excellent news as we already get the N bytes back. So this bytes are … what… padding bytes ?
Anyway, the fact that i got 0 bytes back without any zlib or system error was a relief. But the “dezip” function is returning 0 on error or the size of the decompressed data when everything works…
So… I was considering that the “dezip” function failed even if everything was alright.

The whole issue was fixed in 5 minutes by changing the default error value from 0 to -1….

I spent the whole day tracking this bug…

The Attack of the Patatoids!

Last day i was reading the wikipedia article about the Pioneer program. I don’t know how, but after following some links i ended on the Hayabusa mission article.
The Hayabusa space probe was launch in 2003 to study the Itokawa asteroid. The most ambitious part of the mission was about landing on the astoreid to collect samples. From what i understood, the samples would not have been collected by drilling the asteroid but from the debris made by the collision between the asteroid and a projectile launched from the space probe. Unfortunately, the attempts to land on the asteroid failed. Nevertheless, it seems that the Hayabusa managed to collect some samples.
The Hayabusa may be bak to earth around 2010.

Using the data collected, Robert Gaskell from the Planetary Science Institute generated 3D models of the Itokawa asteroid. The model is available in 3 formats (plate-vertex table, STL ASCII and triangle) and in 4 resolutions (from 49,152 to 3,145,728 triangles).
The plate-vertex table format is similar to ply2 format. So, i took the 3M triangles version. Translated it into ply2 and launched my crappy raytracer on it.
I was surprised by the rendering speed. A 256×256 image was rendered in less than 1 minute. Nevertheless, i had a nasty bug 🙁

Buggy rendering of Itokawa asteroid

As you may have noticed there’s a bug on the left part. Here’s a close up.

buggy correct
Buggy rendering of Itokawa asteroid (close up) Correct rendering of Itokawa asteroid (correct)

The “correct” image was obtained after 3 hours of computation by disabling BVH. So the problem came from the BVH code. After almost rewriting the BVH building and intersection code, i still had the same bug. Some heavy code review later, i realized that the wrong ray intersection was returned. In fact it was the informations of the last intersection instead of the one from the closest intersection point. It’s a very stupid bug. Well at least i cleaned up the BVH code.
So for your pleasure here is a nice 512×512 image of the Itokawa asteroid.

512×512 image of Itokawa asteroid

And some stats:

  • BVH building time : 0h 0min 38.943722 sec
  • Rendering time : 0h 0min 7.411200 sec

As i said before, the code is greatly unoptimized but it manages to render a 3M triangles model in less than one minute. I’ll try to speed up the BVH building code, use a clever cost function and monitor memory usage (while running the top command, i noticed that more than 70% of the RAM (1go) was used.)

Bonus : dark side of the patatoid!

Dark side of the Itokawa asteroid

Having fun with OpenGL

This weekend i played a little bit with OpenGL. First, i helped my brother with some issues using the GL_ARB_texture_rectangle extensions. I never used it before. It’s very easy to use. You just have to use GL_TEXTURE_RECTANGLE_ARB instead of GL_ GL_TEXTURE_2D when you call openGL texture functions (or when you want to enable / disable texturing). The tricky part is that you have to specify that the pixel elements are stored one after the one. Also, textures coordinates values (u,v) are between [0,twidth]x[0,theight] instead of [0,1]x[0,1].

// Enable non rectangular textures
// Generate texture id
glGenTextures( 1, &id);
// Pixel component are stored linearly
glPixelStorei( GL_UNPACK_ALIGNMENT, 1 );
// And now store the texture data
glTexImage2D( GL_TEXTURE_RECTANGLE_ARB, 0, GL_RGB, textureWidth, textureHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, data );

I must admit that i only used it to display a rectangular texture on screen. I found several examples on the web where it was used to avoid to scale the framebuffer when you save it to a texture.

As one of the GGI gsoc student is working on libggigl, i decided to code a little GLX example so that i don’t look stupid if he had questions about it 🙂
Here it is!
There’re no functions, no structures. Everything is the main. That’s what I call pigforce coding.
If I have time, I’ll try to play with offscreen rendering with GLX.

PCEngine tracker status : I’m writing code for hsync and vsync interrupts. It’s mostly a cleanup/study of mkit code. I hope to finish them this week and then start with tile/map management.

Captain’s clog

Aouch… 3 months since last post.
A lot of things happened. First of all i changed job (who said lame excuse?). Then GGI was selected for google summer of code. Guess who is the GGI admin on gsoc.. me :). 2 projects from the idea list were “slotted”. This means that google will fund them. The project i was about to mentor wasn’t selected. Anyway, i hope everything will be alright because some of the selected projects are part of the 3.0 roadmap.
Still about GGI, my current task is to implement Xdbe helper for X target. The task is not easy as it seems. My first try was kinda simplistic and … buggy. Instead of increasing X target speed, it slowed it down. And worst of all, i totally misunderstood the goal of Xdbe helper. It’s not just about swapping the window drawable. In fact, it’s the last and final part of the job. For the moment in X target, all the drawing operation are performed on the window drawable. Multiple buffering is performed by using window clipping. Let’s say we want a visual of 320×240 pixels and 3 frames (in order to do triple buffering, or whatever). We create a parent window with a size of 320 by 240. Then we create a child window of 320 x 240*3. We display a given frame by moving the child window so that the required area becomes visible.
For example, if we want to view the second frame, we move the child window by (0,240).
Back to Xdbe. We don’t need to use window auto-clipping anymore. We can use a single window with a backbuffer attach to it. If we want multiple frames, we can create a pixmap the same way we created the child window or create a pixmap per frame. All the drawing operations will be perfomed on the pixmap. Then on flush, we copy the pixmap data to the backbuffer and swap the window. It’s not as easy as it sounds because i’ll have to reorganize (or completly rewrite) the X target.

On the crbn/ray tracing front. There’s not much coding going on but i’m reading a lot… Ok. Let me rephrase it… I have a lot of papers and books to read 🙂

The pcengine tracker development was resumed this week. I hope to release a test rom for the instrument editor before the end of the month.

And now something different. Yesterday (and today) i rewrote the gallery with javascript and css. The old one was in perl/cgi and had a small oneliner. I still have the code lying around. I’d better burn it for the sake of mankind 🙂 However the only dynamic part in the new one is the image display in javascript, and as i now have this wonderfull blog, i threw the onliner away.
I put a link (“Doodles, drawings, sketch dump…”) to it in the section “My other stuffs”.

Typo negative

I cleaned up the 5×7 font rendering routine. It now uses mkit macros and variables. Here’s a little example of how to use it:

; set string length
lda    #28
sta    <_al

; set string pointer (don't forget to map it before)
lda    #low(string)
sta    <_si
lda    #high(string)
sta    <_si+1

; set vram address where the font will be rendered
lda    #$00
sta    <_di
lda    #$10
sta    <_di+1

; Here we go!
jsr    print5x7

; You can set BAT using the zp var _block containing
; the number of 8x8 bloc written

The code contained in the archive doesn’t need mkit as all the needed macros and variable declarations are included. If you want to use the font rendering with mkit, you’ll only have to include print5x7.asm and contains both the standard 8×8 font, the 5×7 font and datas needed by the font routine.

You can download the archive [HERE].

Shrinked the glyph

I made some mockups for the tracker interface using tile studio. It helped me realize that the standard 8×8 font might be too big. Here’re test images for the instrument and waveform editors.

Instrument editor interface

Waveform editor interface

As you can see, the 8×8 font used in the instrument editor menu is too big. The screen is 320×224 wide and i need to have an area of 256 pixels for the sequence editor. So one way to space is to use a smaller font. I decided to use 5×7 font. But there’s a problem. It’s easy to use 8×8 font as pcengine stores background graphics using 8×8 tiles. And these tiles are displayed using an array (a map). So if you want to print text, all you have to do is to store the font in VRAM and then set the map so that it points to the correct 8×8 tile. The code looks looks more or less like this (in fact it’s a little more complicated or pcengine) :

for(i=0; i<strlen(str); ++i)
    tile[x+i][y] = mapBaseAddress + 8 * ((x+i) + (y * W));

On the other hand, you can’t use the background tile map for 5×7 as it doesn’t fit the 8×8 boundary 🙁 So all we have to do is to render each text in vram. We’ll have to brutally concatenate bits.
In order to keep things a little bit optimized, i decided to unroll the concatenation loop for 8 iterations. Why? Erm… A little example will explain it better than i will.

byte 0: a0 b0 c0 d0 e0 a1 b1 c1
byte 1 d1 e1 a2 b2 c2 d2 e2 a3
byte 2: b3 c3 d3 e3 a4 b4 c4 d4
byte 3: e4 a5 b5 c5 d5 e5 a6 b6
byte 4: c6 d6 e6 a7 b7 c7 d7 e7

This table represents the output of the concatenations of 8 five bits values. We may repeat this for every 8 characters in the string and we’ll be done … 🙂 The following 2 images show the same string rendered with 8×8 and 5×7 fonts (clic them for a x2 zoom).

8x8 font example

5x7 font example

Here’s a marvelous rom demonstrating this breakthrough in computer science 🙂

Color blasting (part 3)

I recently played with median cut quantization. Like octree quantization, color space is viewed as a 3D space. But it uses a top-bottom approach. We start with a box containing all the image colors and then we split it into 2 smaller boxes along its longest side until the number of boxes is equal to the number of desired colors. The child boxes are then shrunk to enclose their color subset. Each color in the palette is then the mean of the colors contained in each box.
I used stl priority queue to store the boxes and get the box with the longest side. As each new box contains half of its parent color. The first subset contains all the colors where the component along the split axis is inferior to the median. And on the other hand, the second subset color component along the split axis are greater than the median. For this i use the nth_element function.
I should have used them for the octree quantization…
Talking about octree, i put all the image colors into one in order to easily map them to the palette.

The result is quite good with the sorcerian images.

Sorcerer images (median Cut 16 colors)

Here’s the RGB color wheel. The error is very important for low color count 🙁

RGB Color Wheel RGB Color Wheel (median cut 256 colors)
truecolor 256
RGB Color Wheel (median cut 128 colors) RGB Color Wheel (median cut 64 colors)
128 64
RGB Color Wheel (median cut 32 colors) RGB Color Wheel (median cut 16 colors)
32 16

I tried to solve this problem by spliting the box along the axis with the highest variance. But the result is not that great.

Sorcerer images (median Cut 16 colors variance)

Anyway! Grab the sources here.