MAX7219 problem

Hello everyone,

I just replied to a thread in Programming Questions about the MAX7219, but I think this is the right place for the question. The thread was unanswered for two month, so I guess it's dead anyway.

The problem is as follows: I wired up a MAX7219 as described in the sample but only attached one row of 8 LEDs. Shouldn't matter, right?

The problem is, the MAX7219 doesn't seem to respond to any data commands at all. All LEDs light up all the time, when power is connected (although the MAX7219 should be in Shutdown mode by default??).

Any ideas as to what's going on here? I can provide pictures of the wiring. Ah and the sketch is the LCDemoMatrix sample program coming with the library...

Many thanks for any suggestions as I am totally lost here...

Ok, got i figured out myself. It seems to be a common mistake, so I try to clarify things for others:

If you experience the aforementioned problem, it means you have the LEDs wired up the wrong way. Even if your 100% sure like me :-) I thought the anodes have to be connected to Dig0 - Dig7, but that's where the cathodes go. Seg X connects to the anodes.

And another thing worth mentioning is that Seg DP is row 0. Not Seg A as one might think.

So simply correct your wiring and it will work.

Welcome to us mere mortals ! 8)

you have the "xxxx" wired up the wrong way. Even if your 100% sure like me :-)

Thanks for sharing.

Electronics is not like building LEGO: Try and try until it fir or doesnt break. It actually is an engineering discipline. Forturnatly for some of us most componets are forgiving to wrong connections (for a while, at low enough voltage, sometimes ... :roll_eyes:)