8x8 LED matrix little issue

Other Hardware General Electronics
1

Hello,
I would like to ask you: maybe you know where to find scheme of 8x8 matrix? I know that this matrix is not common soldered as it ought to be. I am doing the project with 8x8 HOMEMADE matrix and I want to know how I have to connect my matrix.


This is the module I have and the question is: How this matrix looks inside. I mean how diodes are connected there?

![](http://www.futurlec.com/Pictures/LEDM88SM_Circuit.gif<img src=)This is how my matrix is soldered. Do not pay attention to numbers, just look how diodes are connected.


I found this, and tried to connect my matrix... But it doesn't work.

2

Read the datasheet some more. You need a 0.1uF cap and a 10uF cap from VCC to Gnd, and a 10K current set resistor.

Then you need to set up the command registers to tell it how it operates: normal mode, 8 digits/columns, no-decode mode, intensity and one more. You can do that once in setup().
I use SPI.transfer for that:

digitalWrite (csPin, LOW);
SPI.transfer(registerAddress);
SPI.transfer(dataToBeLoaded);
digitalWrite (csPin, HIGH);

Then use the same commands in loop() to update the columns with data to be displayed.

MAX7219-MAX7221.pdf (451 KB)

3

You can confirm the pinout of your LED module with a 5V supply, 1K resistor, and a ground probe.
Connect the resistor to 5V and use the other lead as a probe. Apply the resistor to a pin, and move the gnd probe until you find a LED that lights up. Now you have one anode (5V) and one cathode (gnd) identified.
Leave the 5V connected and find the other cathodes. Over half way done now!
Move the 5V to one of the non-gnd pins, and see which anode it is. Continue. Won't take long to identify them all.

4

Wow thanks a lot I will try and I think everything would be fine. Thank you very much.

5

I bought the same thing on eBay.
I posted about this in one of my previous posts.

It is a row cathode, column anode 8x8 matrix which is what we want to use with the MAX7219.
Googling the part number would have told you that.

Unfortunately, the PCB itself was designed wrong. For it to work, you need to insert the matrix upside down.
Upside down means that the part number printed on the matrix needs to be at the top.

To use the LedControl library, you would need to re-write your code.

If using a different library, you would need to use the rotate function.

6

If using a different library, you would need to use the rotate function.

Or you can use the MD_MAX72xx library (links below) and just tell the library which way the matrix is wired and it will adjust.