The MAX7219 all on issue

Forum 2005-2010 (read only) Hardware Interfacing
1

I'm ripping my hair out over this one... I save posting messages like this for the last resort, and this is it...

I number of people in this topic had the same problem... although no one posted if they got it working and how...
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1145204941/15

My setup is the same as the photo in there, a single 7219 with an 8x8 little matrix...

From what I can tell the wiring from the 7219 to the matrix is not the problem, its the 7219 itself or the code driving the 7219. I've tried every different bit of code I could find that might relate to this issue and the results are all the same... no results.. changing values of leds to display.. clearing.. nothing seems to change the output of the 7219.

Has anyone run into this issue and how did you resolve it?

Thanks...
-tim

2

Hi,

could this be a problem with the DisplayTest-feature of the MAX7219? The datasheet of the MAX7219 says once DisplayTest is activated it overrides all other commands. If you software has an explicit function for this you should set the DisplayTest off right at the start of your code (in setup()).
If there is no explicit function you can always send the MAX7219 OpCode 0x0F for DisplayTest followed by the value 0x00 for switching it off.

In my LedControl-library http://www.arduino.cc/playground/Main/LedControl I switch the DisplayTest off as soon as it get initialzed. Maybe you want to try the Library and one of the Demos Arduino Playground - LedControlDemos for the library to check wether this behaviour is really caused by the Displaytest-feature.

Eberhard

3

Thanks for the reply wayoda...

Its very odd... I tried your Led library again and still have no change. Even with a single led hooked to pins 0 and DP

Is it possible I have fried the chip? is there anyway to tell if its still good?

Grr this is starting to get a bit frustrating. It's supposed to be fun...

Any more tips or ideas ?

thanks again...

4

timmaah,

For what it may be worth, I had the same symptom (all on bright) with the MAX7221 when the CLK pin was disconnected. You might want to recheck that line - maybe put a sound card oscilloscope on it. (It will also buzz your PC speaker.)

You might request a set of samples from Maxim (perhaps the 7221 this time). Too bad they take so long for this particular chip. (Mine took 3 weeks from Asia.)

Good luck - don't give up!