I am in the process of building an 8x48 led matrix to display messages on. (im planning on asking one of my friends to prom by leaving it in her locker). i'm trying to get the display working with only one 8x8 led matrix (they are 24 pin bi color matrixes), I have tried the LEDemomatrix example for the LEDcontrol library and the display does not change. I've checked my wiring and I can't find any problems there. My guess would be that the arduino is not communicating with my MAX7219 but I don't know how to solve the problem. I'm using a breadboard to test the circut on (if that matters) and I did remeber the two capacitors between +5v and GND, also Im using a 27k resistor for iset (my matrixes are rated for 2.2-2.5v at 20 miliamps) has anyone had a similar problem? Thanks.
here's the page for LEDcontrol http://www.arduino.cc/playground/Main/LedControl
here's the page for the MAX72XX http://arduino.cc/playground/Main/MAX72XXHardware
ive attached a word document with a table of what i have attached to each of the MAX7219's pins, i did not mention the capacitors in the document
One suggestion first off is to make sure that the Arduino is pumping data at the MAX7219. All three of the lines should "sing" on a logic probe - flutter between the 0V sound and the +5V sound. I would check that. Your current setting resistor is connected to +5V right? Have you verified that the +5V and 0V pins on the matrix are connected correctly using a logic probe? You have not given us a datasheet on your matrix. Are you sure you have the DIG pins connected to LED cathodes and the SEG pins to LED anodes? Have you actually breadboarded the matrix, for example connecting LED matrix pin 24 to 0V and matrix pin 22 to 5V (through a 200 ohm or so resistor!) to make sure the matrix works the way you think it works?
I hope you have a logic probe. If not, get one. They are very very cheap and you need it to test every pin to make sure it is doing what you think it is doing. An oscilloscope will work too but will take 10x longer to do and probably tell you nothing more you can use at this point.http://www.amazon.com/Elenco-Electronics-LP-560-Logic-Probe/dp/B000Z9HAP4