Some LEDs on my MAX7219 display stay constantly on

Using Arduino LEDs and Multiplexing
1

Hello,
I am currently trying to control the LED pins on an 8X8 matrix using a MAX7219 driver, For this code, I am using an ESP32 module so maybe this forum isn't the best place to post it, however, I have also tried with an Arduino and I'm having the same issue.
Here is a picture of the LED display when it is connected to the board but no code has been applied:

285814950_5181264501909756_3984825086491653906_n
285814950_5181264501909756_3984825086491653906_n1536×2048 107 KB

Then I apply this code meant to display scrolling text:


#include <MD_Parola.h>
#include <MD_MAX72xx.h>
#include <SPI.h>

// Uncomment according to your hardware type
#define HARDWARE_TYPE MD_MAX72XX::FC16_HW
//#define HARDWARE_TYPE MD_MAX72XX::GENERIC_HW

#define MAX_DEVICES 2
#define CS_PIN 5

MD_Parola Display = MD_Parola(HARDWARE_TYPE, CS_PIN, MAX_DEVICES);

void setup() {
  
  Display.begin();
  Display.setIntensity(5);
  Display.displayClear();
  Display.displayScroll("SCROLL", PA_RIGHT, PA_SCROLL_LEFT, 150);
}

void loop() {
  if (Display.displayAnimate()) {
    Display.displayReset();
  }
}

Blockquote

Then the LED matrix looks like this:
(I can't embed more than one piece of media per post because I'm new so I will reply to this post with the video)
But basically it looks like it shows the text scrolling but those same LED's that are always on so you can't really see the text.
I have wired it up correctly, the ground to ground, Vin to Vin, CS to pin 5, DataIn to pin 23 and CLK to pin 18. My current theory is there is an issue with the MAX7219 PCB. If anyone can offer any help I would be grateful, thanks.

1 Like
2

Here is the video of the scrolling code

3

Okay, I'm a moron. I'm tempted to delete this post but I'll keep it on in case there's some idiot out there just like me that is having this issue. The LED matrix was plugged into the MAX7219 driver the wrong way round.

1 Like
4

Nah, you just made a mistake. In doing so and documenting it, you may help others.
Good job figuring it out.

BTW do you have a link to that LED matrix? I'd like to get some of those.

5

I was thinking "Obviously those LEDs have been connected backwards - but how could that happen?"

Of course, it is the way the matrix pins are connected and being plugged in upside down does exactly that - causes some but not all LEDs to be connected backwards.

So we will remember the pattern for the next time someone asks, in case they do not realise it themselves. :+1:

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