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1  Forum 2005-2010 (read only) / Interfacing / Re: Arduino interfacing with Java/JSP on Linux on: March 21, 2008, 10:39:40 pm
absolutely, yes. if you're satisfied with the features and performance of the library, then it should work fine... let me know how it goes, im curious...

Many thanks, just a few more questions :

I am running 2.6.22 linux kernel ( a light one, recompiled without a lot of unnecessary bits). This works perfect in a network standpoint (Apache/Tomcat).

I have installed the arduini soft and driver and I can see the Arduino board. Is that driver enough our shall I use another one ?

In fact, once I have the USB/Serial driver installed, can't I use the API to send command directly to the /dev/TTYsx interface instead of the JNI + Low level C driver ? (A bit like the serial monitor of the arduino software does).

In this case, I can send value to the arduino board from my JSP pages and I need to update the arduino sketch to send all the needed values to the Linux driver.

Many thanks

2  Forum 2005-2010 (read only) / Interfacing / Re: Arduino interfacing with Java/JSP on Linux on: March 21, 2008, 01:04:00 am
the arduino usb port is actually a serial port.. when plugged into your VIA via(ha!) the USB port, its device identification is dev/ttys0 (s1, s2.. etc, pending your device config)

 (I'm also assuming you're running a stable *nix kernel compiled with stable USB/Serial drivers).. you need to code your client side serial i/o in C and wrap it up using JNI.. then you can invoke your JNI layer via your JSP pages (if you fancy doing it that way) or wrap your JNI layer with a nice, good looking interface


Hello, after several time googeling the web, I could not find any answer to my questions !!!

In fact, I would like (as test purpose for the moment) have a linux box based on a VIA Artigo pico On that box, I run apache and Tomcat (Java container) and publish web pages. On the USB, I connect an ARDUINO board with a sketch on it.

What I would like is to have some JSP on the VIA box so that a user can change values and check values to/from the ARDUINO board.

Is it possible, does anyone has done that before ?

Many thanks for help.
3  Forum 2005-2010 (read only) / Interfacing / Re: rgb led 196x32 matrix on: March 19, 2008, 12:07:56 am
Thank you sir.  Yeah. single color led matrix's, I can get my head around that...  but the rgb matrix where I want to control the intensity of each color separately for each led (to give me millions of colors / led), is giving me a headache... I may just try a small 8x8 rgb matrix, 6 colors per led for now..  maybe this is the way to go... anyway, thanks very much for the info...

Here's a place that does them:  you can find out how much they cost from them.

There is a datasheet there - input power requirments were (IIRC) 12V @ 3A. Not huge, but not insignificant either.

As for how to wire it up - modules may be a the right way. One thing I was thinking is that these kind of displays have been around for a long time, going back to the 8080 or Z80 era. It would not have been usual in those days to have many processors. It would probably haev been done with parallel loaded shift registers.

It might give a clue as to how to structure a modern design.

Also, I seem to remember there being a magazine project some years ago, too. (Probably Elector, but maybe the UK magazine Practical Electronic.

Its a good project - certainly gets the brain going.

Just found this kit:

Runs off a single 18 pin 18C54 PIC - no sign of anyother ICs, so must be multiplexing the whole lot. I doubt this is how it is done on the commercial units.

4  Forum 2005-2010 (read only) / Interfacing / Re: rgb led 196x32 matrix on: March 18, 2008, 01:43:44 am
I've consulted an engineer and he suggested I create led modules... he suggested 16x16 .. each module would require its own voltage regulator, microcontroller and drivers.. you could then plug the modules into each other to create the size of matrix desired..  a master microcontroller would be responsible for sending the data to all the modules, as well as syncing, etc...

i never even considered power requirements for when the matrix is entirely illuminated (duh)..

so yeah, im into thousands of bucks..

what I dont get is:  these matrix's already exist.. the DOT furniture store has a 24x168 RGB display (although i think each led can have 6 colors, not 16.2 million).. do you think these displays cost thousands???



a very ambitious project

since you can always buy hardware after the fact, might i suggest not quite investing in the led's right away until you figure out all the hardware?

you may also need to look at using multiple microcontrollers and segmenting the display in order to get reasonable refresh rates my guess is that chaining this many drivers together will not yield satisfactory results. you will probably want segments controlled by microcontrollers that at as frame buffers, and microcontrollers dedicated to feeding display information to those frame buffers. you may also find out that the arduino isn't the best platform for this project. you also need to look at total power usage for the led's which will be quite high.

what do you want to do with the display? that might provide some more opportunity for feedback. do you also have a budget for this project? i would expect it to run easily into the thousands of dollars range.

it's doable though it will just take alot of planning, calculations and cold hard cash smiley-grin do you live near any universities? speaking with seasoned faculty on the subject will answer many questions as well.
5  Forum 2005-2010 (read only) / Interfacing / rgb led 196x32 matrix on: March 12, 2008, 11:40:00 pm
Hello Folks,

As you can tell by my topic, this is an ambitious project.  I've read the FAQs, topics, and such, and I'm sure this topic has come up before, so I'll try and make it unique.  Apologies in advance if I'm asking questions that can be found in these forums.

I'm creating a 196x32 RGB Led matrix.  Before getting down to buying the components, I would like to propose the architecture and receive feedback:

Here's the scope:  196x32 matrix = 6272 led's.

I've decided to use PWM to control the color of each LED.  I would use cascading shift registers to drive each led individually.  This would essentially require 4 outputs from the arduino:  3 for the modulation of the red, green and blue, and 1 for the data being sent to the shift register.  

I'm concerned with driving each LED individually. that it would not be able to achieve the refresh rate required for smooth transitions.  Each LED would be on for a very small amount of time, and on top of that, it would be modulated.  Since only one LED is on at a time, the desired color would be affected as the intensity of each color (RGB) would be dropping to 0 and back up each time the LED is selected/deselected.  

Am I making any sense or am I completely in left field? I've read the article on Charlieplexing, but I'm going to read it again.

Thanks in advance,

6  Forum 2005-2010 (read only) / Interfacing / Re: LedControl help! on: March 14, 2008, 05:30:53 am
Can you post the actual code?  i cant tell if nbr is being clobbered.. you just have a remark that says // update nbr here  ... if the value of nbr is not dealt with in in showPattern, then no LED's will illuminate.. I would suggest stuff like this to aid in debugging:

#define DEBUG // comment out for production to save memory

void showPattern(int nbr){
    if (nbr==1){
#ifdef DEBUG
        else {

#ifdef DEBUG
void displayErrorOnMatrix() {
  // indicate there's an invalid value passed to showPattern()
  // show something i can identify on the matrix, like a big x
  Serial.println("ERROR"); // could expand with the actual error code

  // Draw an X to indicate an error condition (assuming 8x8 matrix)
  // assuming setLed signature is: setLed(?, INT x, INT y, BOOL on_off)
  for (int n = 0; n < 8; n++) {



My name is Carl-Johan and i'm a student at the university of Malmö in Sweden - the K3. Me and some fellow students are making an interactive piece of clothing consisting of a sweater with a sewn on LED matrix on the chest and touch sensors on the back. The LEDs will light in different pattern, depending on what input is given on the user's back.

I'm fiddling with a 8x8 LED matrix via a 7219 at the moment, just for prototyping, and i'm using wayodas LedControl to send data to the chip. Sending data works well, that is sending data once, but when i update the matrix a second time, all LEDs go off!

I was hoping somebody could help me cast som light on this. The basic structure is this:

LedControl lc1=LedControl(12,11,10,1);

void heart(){

  //and so on.....

void showPattern(int nbr){
    if (nbr==1){

 //and so on.......

void setup() {

void loop () {
   lc1.setIntensity(0, 15);
  //update nbr here



Kind regards

7  Forum 2005-2010 (read only) / Interfacing / Re: Guitar loop station on: March 14, 2008, 06:00:27 am
There's a few considerations you need to take into account if you want this to work well:  The following is my recommendation for the pre-sampling - using this allows you to interface quite easily into whatever kit your implementation relies on

First off, it would be easier to use separate AD/DA converters (2 or 4 - you dedicate each converter to handle a slice of the input band .. for a guitar, i would suggest ad1=30-440hz, ad2=441-1260hz, ad3=1261-4400hz, ad4>4400hz - remember, the lower frequencies have greater gain, slicing it up helps preserve the band equalization) with a small built in buffer (say 16k) .. you could FIFO the buffer into an external buffer (you'd need at least 128KB if you want, say up to 2 seconds of audio at 192bps).. The AD/DA converters are built for stuff like this...I'd also suggest to build a small analog mix circuit to mix the guitar output with the sampling audio as opposed to everything being coverted to digital to avoid latency problems.. Then use the arduino as the transposer for driving the input/output delay ratio and to control the buffer timing (flushing the converters to the external memory block across your bus).  Lastly, you need to construct it to isolate the clock frequency harmonics from bleeding into the output (if you care about audio quality)..  If this is a project you are doing for fun, then great.. If it's something you are building just because you need it, then just use protools with the digital sampling/delay plugin... (btw, there are chips that do ALL this for you.  Check out 1Y8839 or the 32H9010 (sfm) both from CampusLabs, ~40$ and ~90$ respectively)


i think im gonna go for it and maybe enter it in that arduino contest coming up at the end of april smiley-wink
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