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Issues with maxim7219 drivers? Answered

I am trying to connect 12 maxim7219s in a daisy chain and am having major issues. Right now I have 7 in the chain and random maxims just randomly don't work (right now, the last two and second one doesn't even turn on). Does anyone have experience with these chips? Can anyone share their experience with them or recommend something better?


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1 year ago

No clue about your circuit...
A general problem with LED display drivers in larger numbers is ripple and voltage drops.
Keep in mind that every time the display changes the voltage drops a bit and the current requirements go up.
It makes sense to use some electrolytic capacitors as close as possible to each maxim to provide a little buffer and filter here.
I assume you used the most basic approach to connect the maximxs to the microcontroller.
Meaning common power supply and individual data connections for each maxim - correct me if am wrong here.
In the Arduino playground you will find quite usefull info for the wiring and use of the mx72 series.

Start with the basics:
Provide a suitable power distribution for the drivers.
For 12 I would recommend at least a 3A supply, preferably 5 to deal with the inrush currents when all LED's would have to go on at once.
If your LED matrixes need a different supply voltage than the maxim consider that the LED's should be isolated from the power supply for the mxims to prevent interference.

Power loop.
For applications like this it makes sense to loop the lines for the power supply to the maxims, LED's and depending on the protcol used also the data power.
Means you wire for example the positive rail from the supply to firt chip, then the sencond,... then from the last also back to the power supply.
Same for the negative rail.
With this you eliminate the problem that the last in line might not get enough voltage due the drops created through the other devices.

Start with a breadboard and wire a bunch of drivers and LED's up as planned.
Only for the power supplies though.
Connect every maxim as a single to test the LED display for the data lines.
Once all are confirmed working as expected start with the first and add one by one.
The worked before as singles and the only thing you changed is to add more data lines to the controller.
If you notice things stuff up see if it is better if you turn just the number 1 on for the LED's instead of doing a full sweep or all lights on test.
If that works fine you most likely struggle with the power supply.
Try to keep the data lines short and make sure they have proper contact.