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Topic: Arduino MAX7219 Library and led matrix question  (Read 735 times) previous topic - next topic

wogoos

Dear Reader
I do have a question about a MAX7219 + LED matrix chip and the software Libraries written for it.
There are two type of these led matrices one like a 1088AX and one like a 1088AX. The difference is the orientation of the LED between the rows and columns. These configurations are called common cathode or common anode. These are reversed in the two AX and BX matrices. The way I look at it is that both matrices can be use in one given design based on a MAX7219 regarding hardware and software libraries used, the only thing that needs to be done is to rotate one matrix 180 degrees compared with the other.
My Question is: Is this assumption right?

I ask this because I'm planning to buy the matrix module from the link below which uses a BX (BS) LED matrix but most of the examples I see make use of a AX (AS) type matrix. I'm worried that the software is not controlling the MAX7219 in a correct way to make the LED's go on and off. That means the LED's need to be forward current activated instead of reverse. If my assumption is correct I can use the standard libraries without any change independent of the matrix type. But if I'm wrong I need to change the libraries and I want to avoid that.

Hope some one has experience with it and can let me know
thanks Oscar Goos

https://nl.aliexpress.com/item/Free-Shipping-MAX7219-dot-matrix-module-Display-module-DIY-kit-MCU-control-module-Special-promotions/1006544892.html
Attached the MAX7219 module and matrix examples files

Paul__B

There are two type of these led matrices one like a 1088AX and one like a 1088AX.
Did you proofread that?

The difference is the orientation of the LED between the rows and columns. These configurations are called common cathode or common anode.
Which is nonsense as both anodes and cathodes are commoned.  The correct terms might be "row anode" or "row cathode".

These are reversed in the two AX and BX matrices. The way I look at it is that both matrices can be use in one given design based on a MAX7219 regarding hardware and software libraries used, the only thing that needs to be done is to rotate one matrix 180 degrees compared with the other.
My Question is: Is this assumption right?
No.  Given the asymmetrical arrangement of the pins on the device, to use the alternate device, you need to completely rearrange the pin connections.

I ask this because I'm planning to buy the matrix module from the link below which uses a BX (BS) LED matrix but most of the examples I see make use of a AX (AS) type matrix. I'm worried that the software is not controlling the MAX7219 in a correct way to make the LEDs go on and off.
As long as the cathode drivers on the MAX7219s connect to the cathodes in the correct order and the anode drivers on the MAX7219s connect to the anodes in the correct order, the display will be illuminated and the "LEDs go on and off" but the pattern will be reflected along a diagonal.

That means the LED's need to be forward current activated instead of reverse. If my assumption is correct I can use the standard libraries without any change independent of the matrix type. But if I'm wrong I need to change the libraries and I want to avoid that.
In the Parola libraries, you merely need to set the correct display type.  You illustrate for example, the "FC-16" version.  You just tell the library that is what you are using.

Attached the MAX7219 module and matrix examples files

marco_c

This may help:
https://arduinoplusplus.wordpress.com/2017/04/14/parola-a-to-z-adapting-for-different-hardware/

The MD_MAX72xx library allows you to select the type of matrix to run:
https://github.com/MajicDesigns/MD_MAX72xx

Parola library referenced is here:
https://github.com/MajicDesigns/MD_Parola

Both can be installed from the IDE Library Manager.
Arduino Libraries https://github.com/MajicDesigns?tab=Repositories
Parola for Arduino https://github.com/MajicDesigns/Parola
Arduino++ blog https://arduinoplusplus.wordpress.com

ieee488

#3
Aug 16, 2018, 02:58 am Last Edit: Aug 16, 2018, 03:10 am by ieee488
https://nl.aliexpress.com/item/Free-Shipping-MAX7219-dot-matrix-module-Display-module-DIY-kit-MCU-control-module-Special-promotions/1006544892.html
Attached the MAX7219 module and matrix examples files

I have built displays using that PCB.
Be sure that the 8x8 LED matrices that you get are 1088AX and not 1088BX.
The 1088BX did not work for me.

Of course, the Chinese sellers may have fixed the PCB layout, but I doubt.

In addition, you will need to insert the 8x8 LED matrix upside down on the PCB.
In other words, when you are looking down on the PCB, the FC-16 lettering must be at the top, and the 8x8 LED matrix side with the part number is also on the top.


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wogoos

Hi ieee488
Thanks for your response I'll keep it in mind.

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