I bought two Rain­bow­duinos from seeed­stu­dio and wanted to play a bit. A Rain­bow­duino is basi­cally a 8x8 led matrix dri­ver with a I2C inter­face. This image shows two rain­bow­duinos, each with a 8x8 RGB Matrix, in action:

 

I used my Pro­cess­ing library and some cus­tom Java code (using rxtx library) to dis­play ani­ma­tions (amongst oth­ers is use the blinken­lights library) on the rain­bow­duino. This lit­tle video is the out­come after some hacking:

2xrainbowduinos + 1xarduino = fun from michu on Vimeo.

pre­view of my rainbowduino/arduino firmware and the java tool to cre­ate some fancy stuff…

I use an Arduino (Duemi­lanove) as ser­ial / I2C gate­way, here is the wiring scheme:



 

I pub­lished my firmware (Arduino firmware, Rain­bow­duino firmware and pro­cess­ing library) at google code.

GPL’ed source: http://code.google.com/p/neorainbowduino/

My firmware is more or less a rip-off of the “daft punk” firmware by Scott C / ThreeFN (Rain­bow­duino firmware) and the blinkM firmware (Arduino) firmware. I removed unused code as I keep my Arduino/Rainbowduinos stu­pid — I just want to send frames from my work­sta­tion to the Rain­bow­duinos. I had to add some san­i­ty­checks to the Rain­bow­duino firmware to make it stable.

Here are some fea­tures of the firmware:

  • Send buffer from your work­sta­tion to the Rainbowduino
  • Sta­ble, run­ning more than 5h (at 115’200 baud)
  • Fast, more than 50 fps with two Rain­bow­duinos pos­si­ble. One frame needs ~100 bytes
  • Mul­ti­ple Rain­bow­duinos sup­ported (I2C protocol)
  • Heart­beat, the Arduino tells you each sec­ond if he is still alive and its error counter
  • Pro­cess­ing library avail­ble to mess with Rainbowduinos

 

How to use the Firmware

 

1) Install Arduino IDE

Get the lat­est Arduino IDE from here, and install it. You also need to install the MsTimer2 library.

2) Patch Arduino I2C library

Per default the Arduino I2C pro­to­col uses 100kHz to com­mu­ni­cate — we need 400kHz. The detailed how-to can be found at the Arduino Forum, here is a short step by step introduction:

The atmega-hardware can do 400 KHz, but you have to tweak the Wire-library in file hardware/libraries/Wire/utility/twi.h. Near the top of the file you see:

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#ifn­def TWI_FREQ
#define TWI_FREQ 100000L
#endif

If you change that to

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#ifn­def TWI_FREQ
#define TWI_FREQ 400000L
#endif

The I2C bus should now run at 400kHz. But you also have to the delete the files hardware/libraries/Wire/Wire.o
hardware/libraries/Wire/utility/twi.o because the library must be re-compiled before it uses the new speed.
(This is done auto­mat­i­caly when you open the Arduino-IDE)

3) Wire up Arduino/Rainbowduino

Con­nect your Arduino ser­ial ports with the ser­ial port of the Rain­bow­duino:



(img source)

This allows us to flash the Rain­bow­duino with the Arduino IDE (I use Rain­bow­duinos with an Atmel 168 uP, NOT the 328!)
 

4) Update Rain­bow­duino Firmware

Upload the Rainbow_V2_71.pde firmware to the Rain­bow­duino (select ATmega 168 board). Remem­ber to change the I2C adress for mul­ti­ple devices, the I2C adress is spec­i­fied in the Rainbow.h file:

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#define I2C_DEVICE_ADDRESS 0x06

5) Update Arduino Firmware

Upload the neoLed.pde firmware to the Arduino. I had to dis­con­nect the Rain­bow­duinos
rx/tx lines — else the upload failed (do not for­get to select ATmega 328 board). If you changed the I2C adresses of the Rain­bow­duino slaves do not for­get to change the ini­tial part:

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  //clear both rain­bow­duinos —
  //hint init will fail if both rain­bow­duinos are not avail­able!
  BlinkM_sendCmd(0x06, serIn­Str, 96);
  BlinkM_sendCmd(0x05, serIn­Str, 96);

6) Con­nect I2C Bus

For I2C, you need 3 cables (SDA,SCL,GND):

  • (+) and (GND) from Arduino to Rain­bow­duino I2C pins.
  • Arduino ana­log input 4 = Rain­bow­duino I2C SDA
  • Arduino ana­log input 5 =Rain­bow­duino I2C SCL

Addi­tional Infor­ma­tion: I2C cable length

Sum­mary from http://www.i2cchip.com/i2c_connector.html#Bus%20Length

  • Use screened and twisted cable for runs between boxes. DON’T twist SDA and SCL together. Look at our bus, and either pair them with gnd, or pair SDA+VDD and SCL+GND
  • Don’t run the bus fast if you don’t need to
  • Run the bus at higher currents
  • Cable length max­i­mal 8m

Use­ful links:

Rainbowduino fun — aka neorainbowduino

12 Comments

  • 1 Icing wrote:

    The title of
    4) Update Arduino Firmware
    and
    5)Update Rain­bow­duino Firmware

    should be exchanged.

    July 8, 2010 at 14:27 Permalink

  • 2 michu wrote:

    Thanks! It’s fixed now.

    July 8, 2010 at 14:36 Permalink

  • 3 mel.o wrote:

    OK look. I’m an artist, I have cool ideas to do for rain­bo­duino but I don’t have the head for all these com­pli­ca­tions. I just want to tell each led what color to be, how bright, and for how long. Is that too much to ask? How much would I have to pay you to set it up for me?

    July 18, 2010 at 23:25 Permalink

  • 4 Andy232005 wrote:

    hello can you help me please I don’t know how to run rainbowduino.java I’ve done as you said but now i’m stuck

    September 12, 2010 at 21:09 Permalink

  • 5 michu wrote:

    hey

    to ini­tial­ize the rain­bow­duino device, use

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        pri­vate Rain­bow­duino rain­bow­duino = null;
        pri­vate boolean ping;
    …
            rain­bow­duino = new Rain­bow­duino( pap­plet );
            rainbowduino.initPort();
            ping = rainbowduino.ping((byte)0);

    then send a frame to the rainbowduino:

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    rainbowduino.sendRgbFrame((byte)i2cAddr, THE_8x8_BUFFER, false);

    cheers

    September 12, 2010 at 21:39 Permalink

  • 6 Andy232005 wrote:

    I’m really new to any­thing java and still don’t under­stand sorry. I’ve got a rain­bow­duino hooked up to my arduino with every­thing ready I want to stick to what your doing as your active I see your updat­ing stuff on google code all the time. Do I need a java ide I don’t know where to write that code Please help me

    September 13, 2010 at 02:11 Permalink

  • 7 michu wrote:

    Cur­rently you need to use eclipse, as my pro­cess­ing plu­gin is not yet fin­ished. You need to use some Pro­cess­ing libraries and the ser­ial libraries (librxtx).

    I’ll pro­vide some exam­ples, once I’ve fin­ished the pro­cess­ing lib.

    regards

    September 13, 2010 at 06:02 Permalink

  • 8 Andy232005 wrote:

    Thank you I did install eclipse last night I’ll fol­low some tuto­ri­als to get me started I’m look­ing for­ward to play­ing with the rain­bow­duino using my lap­top Thanks for your help.

    September 13, 2010 at 09:32 Permalink

  • 9 jbremnant wrote:

    Wow, this is cool stuff. Great job. I fol­lowed the bread­crumbs back to your blog after see­ing your com­ment. How many fps can you get with this set up?

    A bit about arduino’s twi lib — it is inter­rupt based imple­men­ta­tion which I found to be rather incon­sis­tent when I tried to use it on bare­bones atmega chips. I had it work­ing with Wiin­unchuck, but it was pain to get it work­ing. This thread has some good info:

    http://www.nerdkits.com/forum/thread/972/

    If you don’t mind doing s bit of C cod­ing out­side of arduino IDE, i rec­om­mend: http://homepage.hispeed.ch/peterfleury/group__pfleury__ic2master.html

    This one uses polling mech­a­nism and dis­card inter­rupts all together.

    November 20, 2010 at 16:14 Permalink

  • 10 michu wrote:

    I also had some issues with arduino’s twi lib, the inter­rupts dis­rupted by dis­play func­tion if too much i2c data were send. how­ever I worked around this issue by lim­it­ing the data I send to the device — I send only changed frames to the device (using md5 check­sum). To send an RGB image to a rain­bow­duino cur­rently takes about 20ms — so per arduino I can send out 50fps. I save about 50% using my check­sum func­tion, means you get “vir­tual” 100fps.

    November 21, 2010 at 13:04 Permalink

  • 11 gregf wrote:

    hi, nice library. your firmware for the rain­bow­duino is clearer to me than the other ones I’ve found so I can actu­ally try to under­stand what is going on and try to pro­gram my cube to do some­thing interesting.

    I’m curi­ous, how does gamma cor­rec­tion work with your firmware? i can’t find a ref­er­ence to it in the code.

    also, any idea how to use more than 16 color lev­els per chan­nel? the col­ors step notice­ably for me.

    December 23, 2010 at 04:22 Permalink

  • 12 michu wrote:

    hey greg. the orig­i­nal “gamma cor­rec­tion” was done by dis­play­ing the first bright­ness level longer then the 2nd bright­ness level etc. I didn’t like that and choose to use a gamma lookup table (its in the java library: http://code.google.com/p/neorainbowduino/source/browse/trunk/processingLib/src/com/neophob/lib/rainbowduino/RainbowduinoHelper.java). With this map you can improve the col­or­ing (the com­ment from the blog entry: PWM from 0 to 100% duty cycle is accu­rately chang­ing bright­ness in a lin­ear way, the eye sees almost no dif­fer­ence between 75% and 100% bright­ness).
    And I guess you cant use more than 16 color level per chan­nel — as this is a hard­ware lim­i­ta­tion. I didn’t try it though.

    December 23, 2010 at 08:24 Permalink

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