I've been working on building an arduinome for some time (http://flipmu.com/work/arduinome/
) and I'm almost done except for getting the LEDs to light up how I want them to. I've been having major problems with the MAX7219 and after hours and hours of wiring and rewiring (it isn't even that many wires...) I am at wit's end. The strangest thing is that a while ago the LEDs were working perfectly, and then one day they just stopped.
The LEDs are organized in an 8x8 grid, so I have the columns as the digits and the rows as the segments. I am fairly positive everything else is wired correctly, the V+ goes to the 5v on the arduino and the GNDs are both plugged in, the ISET is connected to a 15k resistor to V+. DIN, LOAD and CLK are connected to 4,5,6 of the arduino.
When I plug in the arduino, all the lights light up immediately-- even without any code, and even when in code I explicitly set all outputs to LOW. I don't understand why it would do this, because from the MAX72xx datasheet it says of the initial power-up :
On initial power-up, all control registers are reset, the
display is blanked, and the MAX7219/MAX7221 enter
shutdown mode. Program the display driver prior to
display use. Otherwise, it will initially be set to scan one
digit, it will not decode data in the data registers, and
the intensity register will be set to its minimum value.
There seems to be clearly something wrong with the MAX, but the thing is I have 5 of these things that have essentially never been used before (I ordered the first one, and when that didn't work I ordered two more, and when those didn't work I ordered another two, and now I am just at a loss). Does anybody know what I could be doing wrong?