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Description: This is the medium sized LED Matrix with a backpack that has been designed to take SPI serial input and display any graphics you pass it. All the refreshing and communication control is taken care of by the backpack. It's even reprogrammable! Off, Red, Green, and Yellow colors are available.

Unit comes with an Red/Green Matrix assembled with a RG Matrix Backpack Controller.

Check out the LED Coffee Table tutorial!

Documents:

Dimensions:

  • 2x2" square
  • Max width of backpack including connector pins - 1.0"
Pictures show an example array of RGB matrices. These units do not have the Blue color available.

Comments 31 comments

  • Please update schematic. You are shipping v08 of this board, the schematic indicates v03.
    Thanks,
    Justin

  • Warning: SparkFun “resistorless” design tends to fry led matrix in a few hours in continuous use. I bought 3 of these. 2 led matrix does not survive an hundred hours of working (approximately 10h/day for 10 days). The third display continues to working now, after several hundred hours. I also had several trouble to eliminate the ghosting issue. I solved not daisy chianing led matrix but driving them independently (yes, waste of I/O on the microcontroller, but was the only solution that worked)

  • Why have the LED current limiting resistors been eliminated from the most recent schematic? I’m just trying to understand why they are not needed? Thanks, Carl

  • Please update product images and downloadables to current version (no v. info printed on board but it’s not v08n anymore).
    Svealebor’s pastie’d code with some changes (e.g. rowmap) works for me.

  • Why no current limiting resistors? After doing some calculations, it would appear that the voltage across the LEDs is way to high. The only thing that I can think of is that the software running on these is pulsing the LEDs. Turn on the row, small delay, Turn off the row, large delay. Repeat for all remaining rows. Is this a far assumption? Doesn’t this reduce the life of the LEDs? What happens if the software crashes?

  • So I just got 2 more of these and am trying to daisy chain them together. I’m trying to make my best guess using the RGB examples out there, but I can’t even find any confirmation that these RG matrices daisy chain “out of the box”.

    I’m trying the following code in the setup, for 2 boards, per the documentation:

    // Configure boards      
    digitalWrite(CHIPSELECT,LOW); // enable the ChipSelect on the backpack
    delayMicroseconds(500);
    spi_transfer('%'); // % byte
    spi_transfer('2'); // num boards
    digitalWrite(CHIPSELECT,HIGH); // disable the ChipSelect on the backpack
    delayMicroseconds(10);
    

    However, it’s not working when sending 128 bytes in the loop() part of the code.

    Anyone have advice for daisy chaining the RG Backpacks? Thanks!

    Update 3/10/2012

    I have this working on two screens, but now I’m having a ghosting issue. Please see the forums at http://forum.sparkfun.com/viewtopic.php?f=32&t=31590&p=140963 for more info.

    Update 3/18/2012

    Ghosting issue has been resolved. Please see forum linked above.

  • Does anyone have any working Arduino code for the Red / Green only backpack? I’m a little disappointed that this isn’t working as easily as I thought it would.

    • Hi Mark, Do you still need some example code?

      Also, as noted above by Skaros, this board has an error. Use the ‘SPI Output’ connector as the input and ‘SPI Input’ as the output and it works fine. They mixed up the MISO and MOSI signals.

      Jim

      • Hi Jim. Thanks for the reply. I actually FINALLY did get it (kind of) working. I’m using the code on the Arduino Forums at http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1236098804, with the connections as you and others have noted.

        I’m still having an issue though. My code will only work if the power line (Vcc) is floating. If it’s plugged into 5V on the Arduino (NG) power rail it will not work (Arduino is running on USB power). If I unplug the power line, the matrix will light up with the programmed pattern, and then if I re-plug Vcc into 5V the pattern gets brighter.

        I just updated the code to display an alternating pattern, which will work with Vcc floating, but the moment I plug it into 5V on the Arduino the pattern stops alternating.

        Has anyone seen that or have any ideas?

        • Hi Mark, I only needed a big red/green LED, so I set all values to the same data. It should not be too hard to update the code for patterns instead. I also use only USB power. With an external supply it uses about 250mA. Your USB port needs to be able to supply at least that. Here is my trivial test code for a simple all LED color, red then green.

          #include spi.h  // this forum strips off the angle brackets
          
          // Connect to "Output SPI" JP4 on LED Matrix
          // DIO 10 = CSn  (JP4-3)
          // DIO 11 = MOSI (JP4-2)
          // DIO 13 = SCK  (JP4-4)
          //     5V = VCC  (JP4-5 or JP4-6)
          //    GND = GND  (JP4-1)
          
          const int CSn = 10;
          const int ColorRED = 2;
          const int ColorGREEN = 1;
          
          void setup()
          {
              pinMode (CSn, OUTPUT);
              SPI.begin();
              SPI.setClockDivider(SPI_CLOCK_DIV128);
              SPI.setDataMode(SPI_MODE0);
          }
          
          void loop()
          {
              SetLED(ColorRED);
              delay(1000);
              SetLED(ColorGREEN);
              delay(1000);
          }
          
          void SetLED(int color)
          {
              digitalWrite(CSn,LOW);
              delay(1);
              for (int bytenum = 0; bytenum < 64; bytenum++)
                  SPI.transfer(color);
              delay(1);
              digitalWrite(CSn,HIGH);
          }
          
          • Thanks for your help Jim. That code works great. I just tried a 9V, 600ma wall wart power supply and it’s the same story. Code won’t show up with Vcc on 5V. If I unplug it then LEDs light up and animate. When I plug Vcc back in, then the LEDs get brighter, but the animation (red/green blink) stops.

            I’m stumped right now.

            update

            The above issue does not occur on my Arduino Uno. So there’s something going on with my Arduino NG…

            update

            Here’s a little video of it working side-by-side with a Processing sketch. I’ll update the video page when I have some code to post that goes with it.

            http://vimeo.com/37033773

  • Hey Sparkfun, just wanted to let you guys know that the MISO and MOSI pins on the SPI headers for the RG Matrix backpack are switched around. The “input” header should have MOSI instead of MISO. The schematic is also incorrect.

    I picked one of these up a few weeks ago for a project and couldn’t figure out why it wasn’t working. I ran a wire to the other header of the backpack and it works fine, but this works terribly for any sort of backpack daisy-chaining.

  • Might consider buying it, if I could see PCB from both sides or have a look @ Eagle files.

    • Sry, me posting again - on which legs does it use the decoupling capacitors, on both 74hc595 and uln2803? Thank you wery much. I hope to get a replay from your team :)

      • Placing decoupling capacitors across the power lines near all logic components is standard design practice. If you look at the above schematic, you’ll see decoupling capacitors drawn near most of the parts. These capacitors are located nearby the same parts in the physical layout. The transistor array has bulk and decoupling capacitors near it as it is switching large currents to the LEDs at high frequency. These capacitors prevent voltage spikes from propagating to the rest of the logic circuitry. If you contact us at techsupport@sparkfun.com, we’ll be happy to send you the EAGLE files.

    • There are also no decoupling capacitors in 74hc595 or uln2803 sample applications in manuals.

    • Why does it have decoupling capacitors next to the ULN2803, it’s an transistor array and you don’t decouple transistors …

  • This looks like an interesting project, but I wonder if it would be beneficial to have a choice between internal and external sync for multiplexing?
    With a large array of such matrices, I would expect the EMI spectrum to be pretty gnarly if every module is “doing it’s own thing."
    I am in favor of using a distributed synchronization clock for all LED row/column scanning, and would appreciate any thoughtful comments about this suggection.

  • Can someone please show me the connections for this board with the Arduino Duemilanove?
    Thanks!

    • it’s the same methode with http://www.sparkfun.com/products/760
      but the pin are not in the same place.
      Philippe

  • Hi I’m a newby
    Have just bought an arduino and this matrix. would like to make a simple scrolling clock with them. I cant find a library for this anywhere. Can anyone point me in the right direction?
    Thanks

  • I’ve got some wiring examples that show Ground, SKC, MISO, MOSI, CS and +5V pins.
    But my backpack has Ground, MOSI, CS, SCLK, VCC and VCC pins… can someone help me figure it out?

  • Is it possible to fade the brightness level of each LED? Can we make more than the default 3 colors?

  • What would be the cheapest way to go about getting the front of these to be touch sensitive?

  • Why there are TWO vcc pins for the SPI in/out jumpers?

  • Could you run this at 3.3V instead of 5V? Understand ATMega @ 16 MHz isn’t officially rated for 3.3V, but I have used them over clocked and they work fine. I assume the LED matrix would be dimmer and consume less power which is fine for my application.

  • if I would make dot matrix 32x32.what avr 8535 40 can be used as controllers?
    how do I use this product to support my project?
    how the schematic?

  • The LED Matrix I recieved uses an Atmega 168 while the sample code seems to be written for Atmega 8 with an old version of the gcc-toolchain. I updated the self-control firmware example like thus:
    http://pastie.org/321922

  • I agree, eagle files would be very cool. :)

  • Eagle Files?


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