There are different solutions for driving this popular piece of hardware from the Arduino. If you are not familiar with the
MAX7221 you should start by reading the hardware related documents
The software for driving these chips is covered on several pages:
Matrix-libraryThis is the original documentation for the Matrix-library that was shipped with the Arduino software pre Arduino 1.0. The library supports
MAX7219and only works with Arduino 022 and below. To connect multiple MAX7219s together you wire the clk and data to the same lines but the load data line goes to a different pin, also you must define a new matrix and give it a different name.
MAX7221. It can drive multiple devices and has a specific command-set for 7-segment displays (besides the common Led matrix functions).
MAX7219-Library is another available library that supports cascaded
MAX7219's and some basic matrix functions(e.g shiftleft, shiftright, flip, rotate, raise, lower).
Max72xxPanellibrary implements Adafruit's
GFXlibrary for multiple 8x8 LED displays driven by MAX7219 or MAX7221, in arbitrary rectangular layout. Support for basic graphic primitives and text. Features double buffering to prevent flicker.
More specific problems with the
MAX7221 have been discussed several times on the Arduino Hardware Forums.