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[on:]

Hi,

I try to drive a LED display with MAX7219 and Arduino. I use LTC-2727G common cathode 7-segment/4-digit display, which is previously successfully multiplexed with Arduino. But this time i need more free pins, and  i selected MAX7219 for driving the display.

The problem is, that if i run the MAX7219 7-segment example from LedControl library, all digits show "8", all segments light up, and nothing happens.
I can see that the MAX is writing characters to the first digit (but only there), because the first digit lights up sometimes brighter as the others.
What can cause this? I tried different values for Rset, but nohing changed.
My first thought was a shortage, but for all the 4 digits? Noooo MAX7219 is brand new...  Communication is OK...

Has anybody seen anything like that? Any help would be appreciated...

[Reply #1 on:]

Would be helpful to have a circuit and the sketch.

Have you wired the segments and digit selections the right way round?

[Reply #2 on:]

I will upload the circuit, but i think it is mostly OK. (3 wires to MAX, and from that, wires to the LTC2727...)
It is possible that it is miswired, but i will check only tomorrow (and, miswired? for all the 4 digita? and all segments are lighting? :S ). Sketch is uploaded from LedControl library's example, without changes (except pin definitions).

Schematic and PCB :


Link : http://kepz.atw.hu/1.png

http://kepz.atw.hu/2.png

I had to use lots of wires, due to small pcb size
(It is a desk clock with a thermometer, very simple.)

[Reply #3 on:]

Usually worth trying the really obvious things first.

[Reply #4 on:]

I added scematic adn PCB to the first entry.
I took a short measure, and there is 5V on every digit outputs on the MAX...

[Reply #5 on:]

OK guys, sorry for dumb questions! Error was a miswiring, the Max's Dig4 output was wired to the Adruino's A5, which i used for DIN to the MAX. So it haven't got any data received I think the error happened during the toner transfer, which after i have corrected the wires, whose were not transferred correctly.
Now it is working fine, thanks