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Author Topic: Max7219 and 8x8LED matrix - all LEDs are constantly on  (Read 3371 times)
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Perhaps - do you have a part number? Just about anything can be found on the internet.

This is what mine looks like.  CSM-8826 is on the artwork it the back. Side is marked A5880SRSG-A, which seems incorrect - other A5880 parts I could find are only 16 pin parts.
I think I need to re-do my fonts to turn them 90 degrees for this part.
And do a little experimenting, see where "upper left" vs "lower right" is so the fonts make sense.

I defined an 8x32 array to represent the display, not sure I have that lined up with my chip callouts from left to right either.
So for example if I call 0,0 the lower left, 7,0 the upper left and 0, 31 the lower right and 7,31 the upper right, I'm not sure I'm send stuff there now.
Maybe I should flip it 31,7 for upper left and 0,0 for lower right - probably easier to visualize and keep straight that way.
Then call 3 the left display and go across 2-1-0 to the right.

Was just glad to show the hardware all worked to start - having left off +5/Gnd to 3 chips had me stumped for a bit  smiley-roll-sweat

* CSM88261_red_green_8x8.pdf (266.15 KB - downloaded 20 times.)
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I built my own mini LED matrix. One with a common anode and one with common cathode. The common cathode works brilliantly, the common anode, well I can't get it to work at all. Attached is the schematic for what works and doesn't.
So it looks like I can get either a new set of LED matrix's or the 7221's. I can't think of a way to get this to work any other way...


* LEDMatrix2.png (88.31 KB, 722x837 - viewed 31 times.)
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I built my own mini LED matrix. One with a common anode and one with common cathode. The common cathode works brilliantly, the common anode, well I can't get it to work at all. Attached is the schematic for what works and doesn't.
So it looks like I can get either a new set of LED matrix's or the 7221's. I can't think of a way to get this to work any other way...
Any luck with your matrix? I have same problem with driving bicolor (common anode) matrix. But someone suggested to use a diodes on SEG A- SEG G lines...
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I didn't realize you had common anode bratan.
I was suggesting diodes for common cathode to prevent the max7219 from trying to source current into the cathode when it was put into shutdown mode.

Now that I think about it tho:

In common cathode,  cathode goes to 7219 to prevent it from driving matrix cathodes high when in shutdown
In common anode, anode goes to 7219 to prevent it from pulling matrix anode low when in shutdown

In both cases, the non-driving 7219 is isolated from the common pin so the other part can control the shared line.

I'll draw this up when I get home.
« Last Edit: November 07, 2012, 03:10:01 pm by CrossRoads » Logged

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Dual MAX7219 controlling common cathode two-color array


* DualMax7219array.jpg (86.26 KB, 960x720 - viewed 34 times.)
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And the common anode version, haven't filled it out as much but one can get the idea


* DualMax7219CAarray.jpg (73.58 KB, 960x720 - viewed 23 times.)
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Crossroads, I just built a single 8 x 8 on a protoboard and used your code in this forum...pretty cool...displays a checker board type matrix lit up that shifts back and fourth...nice..
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Thanks Aaron.

If you're seeing the checkerboard, then you are running old code.
I have posted, for you, the new code that works much better.  I suggest you find that.
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Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
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