Pey's Cave

InMoov Finger Starter

2020-01-06T16:20:00.001-07:00

Now that I got the calibrator working (at least for the time being) I have moved on to the actual Finger tutorial. I did have a bit of surface adhesion problems while printing but once that was resolved the steps were easy enough to follow.

There are a few things that are worth mentioning.

The tutorial uses metric drill bits to re-drill the holes int he printed parts. Unfortunately I did not have the exac ones, so I had to use approximate replacements:

3mm -- may need to use a 1/8" (3.2mm)
3.5mm -- may need to use 9/64" (3.6mm)
1.5mm -- may need to use 1/16" (1.6mm)

The instructions also suggest using 3mm filament pieces on the joints but I did not have any. I used M3 bolts instead with nuts to secure them because my slightly larger drill bits had left the holes a bit too large. Since this is just a prctice finger I think it's OK for now, but I'll have to revisit this issue or at least cut the excess off the bolt length.

Even a single servo will probably need more power than what the Arduino board can provide. Be sure to use a battery or other power source. I could not find any specific details on how much current the recommended HK15298B can draw but the best clue that I found online suggests it can be around 2 A, which is a LOT. An average AA battery (don't quote me on this) can provide only about 50mA so instead I found an old power adapter, cut the tip and used it to power the servo.

Once I programmed the Arduino with the provided script, another little speedbump I ran into is that upon the first try the servo did not move. The trick to solve that was to make sure that the power adapter I used and the Arduino shared the same ground. In my particular case I was using USB to power the board, so I just used a wire to connect the ground pin to the ground wire of the power adapter for the servo using a breadboard.

I also noticed that the servo can mechanically move 180 degrees but in reality it only moves 90 degrees. This is something that I overlooked when looking at the list of compatible servos from the InMoov website (It's clearly stated there) and I wasted like an hour trying to figure out why the board did not turn it all the way. My bad.

In the end it all worked out, although I still need to think about the buzzing noise made by the servo when it's at the max position pulling the finger. It makes the same noise even if there's no load, so I suspect it may be related to the low(ish) voltage fro my power adapter, maybe it will work better once I provide at least 6V.

InMoov Calibrator

2020-01-06T14:18:00.000-07:00

I have decided to start the journey of building the famous InMoov robot. I have started with the basic Finger Starter and the very first thing to do is calibrate the printer to ensure that the parts will fit together properly.

I am using an Ender 3 printer, Cura and PETG filament. Upon my first attempt the pieces were so tight that once I was able to forcefully put them together I could not pull them apart.

Calibrator with 0.0mm horizontal expansion

After a bit of searching, I found that others with the same issue had been able to fixing by changing the Horizontal Expansion setting in Cura. They suggested different values, so I had to try for myself. That setting affects the "holes" in the print, negative values means the holes are more "loose". I tried -0.2, -0.4, -0.1, -0.05 and -0.08 mm in that order. Here's some pictures with the results.

Calibrator with -0.2mm horizontal expansion

Printing with -0.2mm left the pieces fit but a little too loose. Then I still went on to try -0.4mm to see how much different it was and the result was as follows.

Calibrator with -0.4mm horizontal expansion

This time the holes were even bigger, by too much. So I moved the other way and tried -0.1mm.

Calibrator with -0.1mm horizontal expansion

That one fit almost perfectly but I still ha dto try to get better results, so I went for -0.05mm.

Calibrator with -0.05mm horizontal expansion

This time the sides fit tight but not too much, the problem was the center rectangle that I could not take apart after trying for a few minutes. So I finally tried -0.08mm...

Calibrator with -0.08mm horizontal expansion

And here I stopped trying! It fit slightly better than -0.1mm and I could remove the pieces easily.

Conclusion: If you are having trouble with the calibrator pieces not fitting, I'd try the Horizontal Expansion setting on your slicer first, your perfect number will be most likely different than mine but somewhere between -0.1mm and -0.2mm is a good place to start.

Programming languages for Web Development

2019-11-15T07:38:00.001-07:00

A web application is usually built with 5 types of files corresponding to different programming languages.

Client side

These files are copied to the users computers via web browser and displayed/run there.

HTML

What's for:

Setting the basic site structure, like what part is text, what's a table, what's a picture, etc...

File extension:

.html

Code looks like:

<html>
<header>
<title>This is title</title>
</header>
<body>
Hello world
</body>
</html>

JavaScript

What's for:

Writing functions that run on the user's side, like get the local time, display alerts, set a timer, etc..

File extension:

.js

Code looks like:

function initCountdown() {
var oneDay = 24*60*60*1000; // hours*minutes*seconds*milliseconds
var today = new Date();
var secondDate = new Date(2017,7,27);
var diffDays = Math.round(Math.abs((today.getTime() - secondDate.getTime())/(oneDay)));
document.getElementById("countdown").text = diffDays;
alert(document.getElementById("countdown").text);
}

CSS

What's for:

Making the app pretty. Font type, color, size, image borders, alignment, some animations, background, etc...

File extension:

.css

Code looks like:

.on-the-day-section .two-column-holder ul li p {
padding: 0 2%;
font-family: "Lato", sans-serif;
font-size: 12.5px;
font-size: 1.25rem;
color: #828282;
text-align: center;
}

Server side

These files are executed privately on the web server

SQL

What's for:

Read and write from/to a database

File extension

.sql

Code looks like:

select first_name
, last_name
, email
, phone
from customers
where name = 'Homer'

PHP/Python/Java/Go, etc..

What's for:

Middle-man between users and database, depending on language it handles security, authentication, serving files, etc...

File extension:

Various (.php, .py, .java, .go, etc...)

Code looks like:

Various, but similar to the JavaScript example.

Que es eso de "formatear" y "particion"???

2014-04-13T00:08:00.000-06:00

Tal vez de pasada has escuchado a un par de aficionados a las computadoras hablando y por ahí mencionaron las palabras "partición" y "formatear". Por si acaso te has preguntado que es eso, aquí esta la explicación "con manzanitas".

Cuando compramos un disco duro nuevecito de paquete no trae absolutamente nada, es como un cuaderno nuevo. Es mas, es como un cuaderno completamente en blanco, sin cuadricula ni renglones ni nada. Ahora supongamos que este cuaderno lo vamos a necesitar para una sola cosa, eso quiere decir que no necesitamos ninguna división y que el cuaderno tendrá una sola sección. Las particiones de un disco duro son como las secciones del cuaderno, siempre vamos a necesitar por lo menos una. Pero ademas de decidir cuantas secciones va a tener el cuaderno (cuantas particiones va a tener el disco duro) también necesitamos renglones o cuadricula para escribir ordenadamente. Para el disco duro, el formato seria como estos renglones o cuadricula. Y de la misma manera que existen diferentes tipos de renglones y cuadriculas en los cuadernos, también existen diferentes formatos para los discos duros que determinan como se almacena la información, si hay algún tamaño máximo que los archivos pueden tener y otros detalles. Estos son los formatos mas comunes:

NTFS(New Technology File System): Es el formato (o mas correctamente llamado "Sistema de Archivos") que usa Windows.

HFS+(Hierarchical File System): Es el sistema de archivos(o formato) que usan las Mac.

FAT32(File Allocation Table 32): En versiones viejitas de Windows era lo que se usaba, ahora se usa mayormente en tarjetas de memoria o memorias USB porque aunque tiene sus limitaciones, es lo mas compatible con diferentes sistemas operativos, por ejemplo, puedes meter una memoria en una computadora con Mac y luego en otra con Windows y las dos la leerían y escribirían sin problemas.

Y... por que habríamos de querer mas de una en un disco duro? Las razones mas populares son:

Tener mas de un Sistema Operativo: Los sistemas operativos mas populares utilizan diferentes sistemas de archivos, y para tenerlos instalados en la misma computadora se requiere tenerlos en particiones o discos duros diferentes.

Separar los archivos del usuario de los archivos del sistema: Esto es especialmente útil para aquellos que tienen la costumbre de reinstalar su sistema operativo a cada rato. Como para eso es necesario borrar todo lo que hay en la partición, es muy conveniente tener todos los archivos que si se quieren conservar en una partición diferente, donde estén seguros.

Combinación de las dos cosas anteriores: Como Windows no puede escribir una partición para Mac y viceversa, a veces es una buena idea crear una tercera partición que sea FAT32 para poner los archivos en un solo lugar y que se puedan leer y escribir fácilmente sin importar el Sistema Operativo en el que estemos en ese momento.

Otra manera de imaginarse las particiones es como si fueran discos duros diferentes, es decir, se puede tomar un disco duro de 500 GB y dividirlo en 2 particiones de 250 GB cada una y a los ojos del sistema operativo parecería que la computadora tiene dos discos duros de ese tamaño en vez de uno. Por ultimo, tal vez te hayas imaginado que "formatear" significaba "borrar todo", esto no es necesariamente cierto. Darle formato a un disco duro es como borrarle los renglones al cuaderno y volvérselos a poner, pero la diferencia es que en el disco duro la formateada hace parecer que el disco duro esta en blanco de nuevo y la computadora nada mas escribe "encima" de lo que había antes. En otras palabras cuando uno formatea, un efecto secundario es que la información "se esconde", por eso es que la mayoría de las veces en vez de realmente borrar todo lo que tiene el disco duro(que es mas tardado), la gente solo lo "reformatea" y empieza a poner las cosas nuevas encima de lo que había antes.

Que es un Sistema Operativo?

2014-04-12T23:32:00.000-06:00

Ah! Otro de esos conceptos que nos hacen esconder la cabeza en la tierra... Hoy veremos que no hay que ser un experto en computación para saber qué es un sistema operativo.

Si fuéramos a una tienda de partes de computadora y compráramos todo nuevecito de paquete (Procesador, RAM, Disco Duro, etc...) y la armáramos nosotros, al momento de prenderla no haría NADA (con excepción de mostrar una pantalla con la marca de la motherboard), solo aparecería un mensaje diciendo "No hay sistema operativo" y ya. Con las computadoras de marca esto no sucede porque desde la fabrica le ponen en el disco duro el sistema operativo y cuando uno la compra parece que siempre estuvo ahí. Digamos que el sistema operativo es el programa mas indispensable que necesita una computadora para funcionar, lo primero que hace tu computadora en cuanto la prendes, antes de darte el control a ti.

Si comparáramos a una persona con una computadora, cuando un bebe nace, ya viene con un sistema operativo "preinstalado" que controla las funciones básicas de su cuerpo, como respirar, los latidos de su corazón y todas esas cosas que ya nació "sabiendo". La diferencia es que una computadora requiere que el fabricante o el usuario instalen (le enseñen) un sistema operativo para que haga lo mas esencial. Ya con el bebe realizando sus funciones sencillas, con el tiempo uno le va enseñando a hablar, caminar, dibujar, escribir, etc... y a una computadora que ya tiene un sistema operativo instalado ya le puedes instalar otra cosas, como un messenger, algo para usar Twitter, iTunes para sincronizar tu iPhone, etc... hay una infinidad de otros programas que le puedes poner DESPUÉS de que ya hay un sistema operativo que los coordine.

Bueno, y ahora que ya quedo claro lo esencial que es un sistema operativo, agregare que en estos tiempos en los que las computadoras son muchísimo mas poderosas que hace dos décadas, los sistemas operativos ya no nada mas traen "lo básico". Con el paso de los años la gente que hace los sistemas operativos les han ido poniendo mas cosas, de manera que ahora, volviendo a la comparación con un bebe, los chamacos ya nacen hablando, escribiendo y hasta jugando fútbol. OJO: no porque tu sistema operativo ya viene con cierto programa pre-instalado no quiere decir que es la mejor opción, tu puedes después instalar uno que haga lo mismo pero mejor o que te guste mas.

Hay muchos sistemas operativos, pero los mas conocidos y que seguro has escuchado mencionar por ahi son:

Windows

Hecho por Microsoft, este es el que viene pre-instalado en la mayoría de las computadoras personales y muy probablemente lo que estas usando ahorita. La versión mas reciente es Windows 8.1 y se espera que Windows 9 salga en Abril del 2015. Otras versiones mas viejitas de Windows son Windows 7, Windows Vista y Windows XP.

Mac OS

Hecho por Apple. Este viene pre-instalado en todas las Macs. La versión mas reciente es Mac OS 10.9, tambien conocido como "Mavericks". Algunas versiones mas viejitas son Snow Leopard (10.6), Lion (10.7) y Mountain Lion (10.8).

Linux

Este es mas bien como una familia de sistemas operativos, muy parecidos entre si. Muy poca gente los usa pero son bastante populares en servidores que las empresas usan para cosas especificas, por ejemplo para ser el lugar donde "vive" una pagina de Internet. Como en su mayoría son de "Código Abierto" (el que sepa programación le puede hacer los cambios que quiera), hay muchos sabores diferentes, muchos de ellos gratis. Dos de los mas conocidos (o menos desconocidos) para "uso personal"son Ubuntu y Fedora. Las empresas usan otros sabores, por ejemplo Red Hat Enterprise Linux y SUSE Linux Enterprise Server

Android

Estamos en el futuro! Ya casi todo mundo trae en la bolsa una computadora con la que (entre otras cosas) hace llamadas. Uno de los sistemas operativos que hacen funcionar muchos de estos modernos teléfonos y otros aparatos móviles es el cada vez mas famoso Android, de Google. La versión mas reciente es 4.4, "Kit Kat". Cabe mencionar que cada versión tiene nombre de algo dulce, como Honeycomb(3.2), Ice Cream Sandwich(4.0) y Jelly Bean(4.1).

iOS

Hecho por Apple, es el sistema operativo con el que funcionan el iPhone, iPod Touch y iPad. La versión mas reciente es 7.

Hay muchos, muchos mas sistemas operativos por ahí, algunos realmente sencillos y que no hacen mucho. Algunos los puedes ver fácilmente (como los ejemplos de arriba), otros nunca los veras pero hacen funcionar muchos aparatos electrónicos. Pero bueno, si antes no sabias, ahora ya puedes decir que sabes lo que es un sistema operativo.

Tu procesador y sus Gigahertz (GHz)

2014-04-12T12:38:00.000-06:00

Uy, que miedo... Gigahertz!!! Seguramente una que otra persona lee esa palabra y su cerebro se cierra creyendo que todo lo que tenga que ver con eso va a ser complicadisimo e imposible de comprender. Hoy vamos a ver que no lo es.

Separemos la palabra en dos: "Giga" y "Hertz".

Giga: Cuando mi madre me mandaba por las tortillas, usualmente las compraba por kilo. Dicho mas correctamente, por kilogramo. "Kilo" no es mas que un múltiplo (1000) de la unidad de medida, en este caso el gramo. En otras palabras, cuando llegaba a la tortilleria y pedía "un kilo", estaba pidiendo 1000 gramos de tortilla. "Giga" es un múltiplo también pero mas grande (1,000,000,000), o sea que un Gigahertz es igual a mil millones de hertz. Bueno, y ahora que son los hertz?

Hertz: Así como metro es la unidad de medida de distancia, litro es de volumen y segundo es de tiempo, Hertz es la unidad de medida de frecuencia. No entres en panico todavia! Frecuencia no es mas que una palabra elegante para decir "veces que pasa algo durante cierto tiempo". En general, un Hertz simplemente quiere decir "veces por segundo". Pongamos un ejemplo sencillito: si una persona esta aplaudiendo rápido, digamos 5 veces por segundo, esta aplaudiendo a una frecuencia de 5 Hertz. Así de fácil.

Entonces... que es lo que pasa 2,000,000,000 veces por segundo en tu procesador de 2 GHz??? Todos los procesadores tienen un "reloj" que les marca el paso para que hagan sus operaciones. Los gigahertz del procesador son nada mas y nada menos que el numero de "tic tacs" por segundo del "reloj". Entre mas "tic tacs" por segundo(mas GHz), mas cosas hace tu procesador en menos tiempo.

Felicidades! Ya sabes que son los gigahertz del procesador. Ahora nada mas una advertencia para cuando andes en busca de una computadora nueva: No siempre el procesador de mas GHz va a ser el mejor, aun hay mas cosas que considerar pero otro día escribiré acerca de eso. Por lo pronto dejare aquí una tablita que encontré con los múltiplos de 10 para el que quiera repasarlos (y recordar el tiempo en el que vio esto en la escuela).

How NASA fixed a computer on another planet

2013-11-11T23:05:00.001-07:00

I just love it when something that sounds like science fiction is actually true. In 1997 the Mars Pathfinder landed on Mars but after a few days it started having trouble: the computer was "crashing" and resetting, preventing the pathfinder from finishing its daily tasks, which it resumed until the next day.

If you are interested on the technical details, you may find them HERE, in the words of someone who actually was involved in the mission. If you are curious but want a quick and simple explanation, I'll try to provide it here the way I (as a noob) understood it.

Super quick overview of the system:

The Pathfinder was controlled by a Real Time Operating System (RTOS), a software that has as one of its main characteristics the ability to schedule the tasks that will run in order of priority and even "pause" them if something with high priority comes along.

The CPU was connected to a Bus, which is a sort of "pathway" shared by different devices, one of them called ASI/MET, used for gathering meteorological data. The access to this Bus was controlled by the RTOS in two tasks with the highest priority in the entire system.

What went wrong:

One of the fun things of RTOSs is that sometimes a variable is used by two different tasks but you have to make sure only one of them is changing it at a time. You can protect the access to this variables using yet another variable called "semaphore" that a task can "take" when it's going to access the variable and "release" when it's done with it. If a task needs access to a variable but the semaphore is "in the hands" of another task, the task is put on hold until it can take it.

Now, imagine that a low priority task takes a semaphore but then it gets "paused" before it can release it because the RTOS needs to run a higher priority task. And then other higher priority tasks keep getting in the way so that the poor little task that has the semaphore never gets a chance to continue. Finally, imagine that a super important task has to run but it needs the semaphore... yeah, that's a problem.

In a nutshell, that's what was causing the problem with the Pathfinder. The low priority task that controlled the ASI/MET took (and didn't get the chance to return) a semaphore that was also needed by one of the high priority tasks that controlled the Bus, preventing it from completing. When the other task that controlled the Bus tried to run, it saw that the first one didn't complete, it figured something was terribly wrong and declared the error that started the reset of the entire system.

How it was fixed:

Once NASA figured out what the problem was, after carefully making sure that wouldn't break something else, they enabled a feature in the RTOS called "Priority Inheritance". This feature pretty much allows the priority of a task to be "bumped up" if it's holding a semaphore that a higher priority task needs. To apply the change they didn't transmit to the Pathfinder an entire new copy of the software, they just sent the pieces that needed to change and then the system "patched" itself.

And that was it... easy... right?

Scratch that!

2013-10-31T22:34:00.000-06:00

Yeah, I thought I was going to write more often but then got a job. That was 8 months ago... Last week, a possibility of a better job came along. Why is that relevant to this blog? Well, I'm still waiting to hear from my potential new employers and while I was reflecting on my interviews I realized that my coding style left much(really, a lot) to be desired. I came to the conclusion that even if I don't get that position at least I got the desire to do things the right way, starting with the readability of my little projects.

So, whatever little code you may find here that was posted before today, please excuse the horrible style. I will try to do better from now on.

EDIT: One of the things that helped me prepare for my interview was an article called "Twenty-Five Most Common Mistakes with Real-Time Software Development" by David B. Stewart, PhD. I liked it a lot and I feel that it applies to other types of development, not just Embedded Systems. You may find the article HERE. Just in case, I have also kept a copy HERE, I hope that doesn't bother anyone...

A few more notes about 7-Segments display and IR receiver on Teensy

2013-05-12T20:47:00.002-06:00

You may have noticed that I hooked up the Teensy board straight to the 7-segments display... That was probably not the best practice for a couple reasons: 1) It would probably be better to use the board to drive the display through transistors or a controller IC instead of using it to actually power it. 2) That's a lot of pins used. This was just an exercise to practice programming on Teensy.

Just as a reminder, here's a picture of it and it uses the NEC protocol.

And before I forget, here's the list of decoded IR commands from my remote.

Vol-	FD00FF	Play/Pause	FD807F	Vol+	FD40BF
Setup	FD20DF	Up	FDA05F	Stop/Mode	FD609F
Left	FD10EF	Enter/Save	FD906F	Right	FD50AF
0/10+	FD30CF	Down	FDB04F	Back	FD708F
1	FD08F7	2	FD8877	3	FD48B7
4	FD28D7	5	FDA857	6	FD6897
7	FD18E7	8	FD9867	9	FD58A7

Anyway, if I ever complete my Space Invaders in Teensy and Spartan project, I won't be using this display, I will most likely use the display on the Spartan board.

IR Receiver on Teensy

2013-02-25T01:41:00.000-07:00

For the past few days I've worked on the first building blocks of my Space Invaders project. As of right now, the approach I've decided to take is to have the Teensy board take the inputs from an infrared remote and control most of the game logic there and then send some display information, like the position of the different objects on the screen to the Spartan-3 board (maybe via Serial port) and have the Spartan-3 do all the display work through its VGA port.

I have been working in the VGA controller and video memory on the Spartan-3 (more on that later) but I took a break from it to work on the controller for the game. Basically, there is only need for 3 buttons: left, right and fire. Maybe I'll add extra functionality after the basic part is done and use some other buttons, but for now 3 is all I need.

This was my first time using the Arduino environment to program Teensy(or anything), which is compatible with it as well as with C. I was glad to find the many libraries at my disposal. I started with Ken Shirriff's IRremote library and added my 7-segments display with slightly different code than the one I used last time to make its timing more independent from the rest of the program. I also used a piece of an old Ethernet cable for the wiring to make it nicer and avoid the mess from last time.

My IR remote uses the NEC protocol and Shirriff's library worked like a charm, I only added a few lines of code to account for held-down keys so the code for the key pressed keeps repeating instead of changing to the special repeat code. The above picture is of the 7-segments display showing the last 2 bytes of the decoded result, which in the case of my remote, are the only ones that change.

As I mentioned, this is just part of the Space Invaders project, so the code for this sill be available on GitHub HERE. The 7-Segments display files can be reused as a basic library, just keep in mind that the pin assignments are defined in the .h file.

What's next?

2013-02-21T16:56:00.001-07:00

Remember all that hardware I got last year? Well, I finally have some time to start playing with it! I still don't have any original project to work on, therefore, in the meantime I will be doing an adaptation of one of my old school labs to practice, focusing especially in my coding style because I am well aware of my deficiency in that area.

A couple years ago, for my embedded systems class, we replicated the space invaders game on a Xilinx Virtex-II Pro board. Sadly, I didn't catch in video the finished product and the only thing I could find was this video of me testing part of it:

So, for my practice project I think I'm going to do the same thing but this time I'll use my Teensy++ and Spartan-3, which is by far less powerful than the Virtex-II, and adapt some of my old VHDL code to build everything again from scratch. As of right now I haven't really considered the limitations of my current hardware now that I won't have a "fancy" PowerPC processor and 2GB of RAM, but the plan is to program a part of the game on each device and get them to talk to each other. This way I get to practice on both of them and also learn something in the process of making them interact. It should be doable... right? ....right?

Anyway, once I get started I'll post my code on GitHub for everyone to see, just keep in mind that it will be a long-term, always work in progress thing for learning and practice purpose only.

Pey! Where have you been?

2013-02-21T15:07:00.002-07:00

Wow, it's been almost a year since my last post. I had to set aside my little projects because 2012 was my last year in college and since I left the best classes for last, I had to focus on them. My last semester was especially interesting, as I did my senior project and learned a little about android development, something that I hadn't even touched before. In a nutshell, what my team and I did was develop an android app for a Galaxy Nexus to drive a little toy truck using its GPS, compass and camera receiving target locations from another android app developed for a Nexus 7 tablet via the internet.

The tablet app had a map to select destination points and a couple testing functions as well as a D-Pad for manual override. It looked like this:

We used OpenCV to make the camera look specifically for orange cones and avoid them. Here's a video of the last test we ran of the completed project (I'm the guy in the red jacket):

I admit there was some room from improvement here and there, but given the time we had to do it and the fact that we really didn't know anything about android development or computer vision when we started I think we did great. And with this I said good bye to college and I am officially an Electrical Engineer! Yay!

7-Segment display, now on Teensy

2012-04-09T14:26:00.000-06:00

Finally, after a few setbacks, I was finally able to play with Teensy and learn how to program it. Here's a few notes on that.

Looks like the numbering convention for the pins on an IC is as follows: Take the IC (or in this case the display) and with the top facing you and the notch on the left side, pin number 1 will be the one on the lower left corner and the numbers will increase to the right and then continue from the upper right corner to the left. I can't believe I did not know this.

Another thing I noticed is that not everything is low asserted like it was on the Spartan board, here only the segments and the cathodes for the colon and apostrophe are low asserted. Otherwise, the display works pretty much the same, with only one digit on at a time. Here's a little clip of the display slowed down:

I used C to program Teensy and by the way, it's super easy to download the program to it, once you have it setup just press one button and that's it. The finished product looks like this:

I must mention that I haven't made my code very portable, the digits are hard-coded but with a few tweaks it can take inputs. I'll add that to my to-do list and post it somewhere in here later.

I got the display from www.robotshop.com, they have the correct pinout but just in case:

1: Digit 1 - 16: B
2: Digit 2 - 15: G
3: D - 14: A
4: Colon Anode - 13: C
5: E - 12: Colon Cathode
6: Digit 3 - 11: F
7. Decimal Point - 10:Apostrophe Anode
8: Digit 4 - 9: Apostrophe Cathode

Teensy has ports of 8 bits each one, with each bit corresponding to one pin. The way I wired them was:

PORTB(0 to 7) : Segments A to G and decimal point.

PORTC(0 to 3): Digits 1 to 4.

PORTC(4 to 5): Colon and apostrophe cathodes.

PORTC(6 to 7): Colon and apostrophe anodes.

I have uploaded all the files HERE, feel free to take a look. I do not claim this is the best way to implement this simple display, I would actually be grateful if you leave a comment with a suggestion on any clever way to do it better.

Defective display + noob = Waste of time

2012-04-04T11:57:00.002-06:00

And add to that an old breadboard. I was very excited to do my first Teensy little project, just to learn how to use it, but nothing worked the way I was expecting. Only 2 segments were being displayed. At first I thought I had wired something wrong. I checked the pinout for the display. The vendor's webpage said that the manufacturer's documentation was wrong and provided the right one. And it still didn't work. I thought maybe I was reading it wrong, to be honest I did not know the convention for numbering pins on an IC. I just got confused.

Finally, I decided to just map every pin to a switch or button on the Spartan board (I even had to use a couple generic pins) and just see where it took me. After several minutes of trial and error I realized that the pinout from the vendor was right. At that point I was wiring everything the way I should. But some of the segments were still not turning on. So I tried the extra display I bought. Bingo! (kinda) All segments except one turned on! After checking the connections I suspected either a pin on Teensy or the breadboard to be the problem... And luckily it was just the breadboard.

It's going to be a little annoying having to use a separate breadboard for Teensy instead of using the one on the Spartan add-on board but I'm OK with that. So... I just have to make a few adjustments and I will post the seven segments display code now with Teensy here.

7 Segments display on my Spartan

2012-03-31T11:55:00.001-06:00

I decided to start my VHDL review with the 7 segments display controller for the Spartan 3 FPGA Board. I have to admit that I cheated a little bit and reused most of the original code I used for my class. I just added a little extra functionality and comments to my code. Before I post the code, let's review the way this 4 digit display works.

Now, you may have thought there should be 7 signals to drive each of the 4 digits and 4 for each of the possible decimal points, a total of 32. However, there are only 12 signals that control the display: 7 for the segments, 1 for the decimal point and 4 to select which one of the 4 digits is active. This is a clever way to save 20 inputs and adds just very little difficulty to the implementation. Because of this, only one digit can be on at a time. So... how come we see all 4 on? It's just a matter of turning them on and off in a cycle so fast that the human eye won't notice when they're off. If we slow down the cycle enough we can see it:

Display slowed down using a 26 bit counter

The way I have adjusted the speed of the cycle is by making a counter large enough (16 bits for the final version) so that the 2 most significant bits take a while to change when the number is being increased by one every clock cycle. Those two bits are the select signals for the multiplexers that pick one of the digits and its value to display. I tried to see what happened if the counter was smaller and noticed that the digits started to get all blurred together. After fixing that, I took a picture of the working display:

"Finished product"

I almost forgot to mention: all the signals for the display are "Low asserted", which means that "ON" is 0 instead of 1 and "OFF" is 1 instead of 0.

Finally, HERE is the VHDL code and its corresponding .ucf file(the one that matches the signal names to on the code to the board signals.

Ready, set, go!

2012-03-27T00:49:00.001-06:00

Today I finally got in the mail the equipment I am going to be using for my little beginner's projects and I am so excited!!! My school renewed some of the equipment in the digital lab and sold the old FPGA boards for a very tempting price and I couldn't resist. Here's what I got:

I had to get a power adapter for the board and a parallel port for my computer but I can start downloading my little baby steps now. I also got a little Teensy++ USB development board. That one I got because I was originally intending to use it for a project that a friend from business school asked me to joint but when the team decided to go on a different direction I was already very interested in learning how to use it so I bought it for myself. Here's a picture that shows how tiny and cool (at least for me) this thing is:

And finally, as I was browsing the web looking for projects I stumbled upon a little infrared remote and receiver and bought them as well. Yeah, I wish I were not a poor student, then I could buy more stuff I don't know how to use (yet). And yes, I also took a picture of that:

In the end, I still don't know what I am going to do with all this but in the meantime I will lean how to program Teensy, start reviewing my old Lab files to get my VHDL skills back and will be posting my progress regularly. Maybe I can come up with a larger project along the way. For now, it's time to go to bed.

Text in forms disappearing on Adobe Acrobat

2012-03-26T16:27:00.002-06:00

I just ran into an interesting issue at work. User 1 sent a PDF form to User 2. When User 2 was done and sent it back, User 1 could not see the text entered in the form unless she clicked on the field and then it would only show that field.

Turns out that this is a know problem with PDF form filled on Mac OS X. Someone smarter than me made a fix, here it is:

Windows Vista (And I tried it on 7 and it works):

1. Download this script
2. Close Acrobat
3. According to your operating system, copy the downloaded script on the corresponding location:

Windows XP:

C:\Documents and Settings\USERNAME\Application Data\Adobe\Acrobat \9.0\JavaScripts

Windows Vista (And I tried it on 7 and it works):

C:\Users\USERNAME\AppData\Roaming\Adobe\Acrobat\9.0\JavaScripts

Mac OS X:

/Users/USERNAME/Library/Application Support/Adobe/Acrobat/9.0_x86/JavaScripts

4. Open Acrobat

5. On the "Edit" Menu, click on "Fix Field Appearances". Done!

Note: The path is for Acrobat 9, but I tried it on Acrobat 10 and still works, at least on Windows 7.

Al credit goes to the smart dude who made the solution. Here's where I found it.

Computacion con manzanitas

2012-03-25T17:14:00.001-06:00

Estaba muy emocionando platicando con mi mujer acerca de mi primer y unico blog (este) y se nos ocurrio que una seccion podria ser dedicada a compartir principios sencillitos de computacion para aquellos que tengan la curiosidad de aprender. A diferencia del resto del contenido este sera unicamente en Español, con el objetivo de que tanto mi mujer como otros que se sientan mas comodos en este idioma lo aprovechen mejor.

Dicho esto ahi van mis dos primeras grandes sugerencias para aprender a sacarle mas jugo a la computadora:

No tengas miedo a descomponerla: Es casi imposible echar a perder la computadora simplemente moviendole a los programas y picandole por aqui y por alla. Aunque es posible dejar la computadora inutilizable por un rato y requieras la ayuda de alguien mas experimentado, solo el danio fisico puede llegar a ser irreparable. Mientras no la eches al agua o la agarres a martillazos todo estara bien.
Siempre ten una copia de seguridad de tus archivos: Utiliza alguna memoria externa a la computadora para guardar un respaldo de tus archivos, de esta manera en caso de robo o perdida total de la informacion en la computadora no pierdas para siempre tus fotos, musica y documentos.

En el futuro publicare en este blog algunas "Definiciones marca Pey" para ayudar a entender esos conceptos que a primera vista se ven complicados. Solo es cosa de perderle el miedo y darse cuenta que es mas facil de lo que parece.

Dual boot Mac and domain logon problem

2012-03-23T16:14:00.000-06:00

Yesterday something reminded me of a stupid problem I had last year. I am one of the administrators for a computer lab at school and during our big yearly re-image and update of he computers I noticed I was having problems logging in after putting them on the school's domain.

The problem was that after adding the computer to the domain on the Mac side, once I tried it to add it on Windows side the "link" would be messed up and since we were using a domain account to log in, we were stuck with just the local account.

The solution/workaround was to remove the workstation from the domain (both at the workstation and the Active directory Users and Computers list) and then add it on the Windows side FIRST and then on the Mac side.

I don't know if an update or the IT people have solved this little issue yet but I document it just in case anyone comes across something similar.

Outdoors!!

2012-03-22T21:20:00.001-06:00

So, I am taking and outdoors recreation class (I needed something easy to balance my load this semester and that was the only thing I could get) and we went to a rope-climbing-course-thing-place. No mames! Now every single muscle in my body is sore. But it was awesome! I am starting to realize there is cool stuff outside of my cave (not that there is anything cool here anyway).

BTW, I had noticed it before, but today I found more evidence of my aversion to sunlight:

This picture was taken at noon. The door at the bottom is the bathroom, guess which one is La Cueva del Pey.

I have a midterm, I have a midterm...

2012-03-21T15:34:00.001-06:00

Yeah, but it is easier to get distracted and start a blog that will probably die in 2 weeks. If you happen to be one of the < 10 people who will visit this blog, here's a few DISCLAIMERS:

This is my first blog ever, it was never intended to be a good blog, it's probably lame and I'm OK with it.
I'm Mexican: You will find Spanglish and/or Spanish.
I used to be obsessed with spelling but I don't care about it or grammar anymore. (Pero nuunk boi a ezkribir asii, m kstra la gnte k lo haze!!!)
No tengo "Enie" ni acentos en mi teclado y me da hueva solucionarlo.
I might (highly super most pinche likely) use inappropriate language

I might add more to that list eventually.

And now, let's get started with this "blogging" thing.