Working on a project using 4 max7221 ics and have gone so far as having 4 completed boards all connected to an 8x8 matrix. Problem is it just lights up and flickers whenever it gets power and does not respond to any data input. Any help would be appreciated..
Note "whenever it gets power".
In other words, without even any code running.
Note that the latch line should have a 10k pull-up.
If it still lights up on power-on and no code (just run "Blink"), then you have either installed the matrix upside-down, or have confused anodes and cathodes (by having the "B" version instead of the "A" or vice versa). Mind you, that should not be able to happen with the MAX7221, only the MAX7219.