MobiFlight Community Support

Good afternoon:
I am trying to mount a MAX7219 Led Display on an Elegoo MEGA 2560 R3 board (Arduino compatible).
I have read all the topics on the Mobiflight forum, I have seen the tutorial, and all the content posted on Discord on the topic.
I am unable to get the LED to work. I cannot perform the test correctly and show 12345678 as indicated in the tutorial. I bought 5 LED modules on Amazon and none of them work. I bought another 5 on AliExpress and neither. I have checked the soldering of the modules and verified that there are no cables that can move... I first connect the LED module to the board, then I connect it to the USB port and then I run Mobiflight. The most I have achieved is that it shows 123 5 78. Other times it shows 0.000 000.0 or strange characters. I have read that the problem may be with the LEDs themselves, which may be bad.
I don't know what could be happening. Does anyone have this type of LED modules and does it work?
Is there a brand or supplier of these LED modules that any of you know works correctly? Could you tell me which one and how to buy them?
I wonder if it isn't a software issue...
Thank you very much for the help.
Excuse my English, I'm using Google Translate
Manuel

Hi Manuel,
I'm facing the same issue.
Beside soldering and connections it can be a power problem.
The Arduino simply can not give enough voltage to the MAX7219 modules.
The first 1-2 modules should work, but when you connect all of them the power coming from the Arduino may not be enough.
In this case external 5V (VCC + GND) should be connected to MAX modules.
Not external power to the arduino via the jack, since arduino powers itself correctly via USB. But external power to the MAX modules and you have to connect the GNDs together.
Check the forum topics. E.g. these:
https://www.mobiflight.com/forum/message/25063.html
https://www.mobiflight.com/forum/topic/6239.html
Regards,

Thanks for your answer. The problem is that none of the displays work correctly (only 88888888 appears and when I do the test everything turns off). My question is: does anyone really have the MAX7219 led display working?

Definitely yes.
Check Karl's videos and info here:
https://www.737diysim.com/copy-of-wiring-led-s-to-arduino-1

Thank you very much for the reply. I am testing with a single display connected to the arduino board and it does not work, and I have checked solders, cables, etc. Anyway, I'm going to look for an external 5v power supply and check if that's the problem. Thanks again

Good morning and Merry Christmas to All.
I still have problems with the displays. I have bought a 5v 20A power supply, I have connected it as indicated in the forum (GND connected to the arduino and VCC to the power supply, I use pins CLK 23, CS 25 and CLK 27), I have changed cables, etc. etc When doing the test I can't get 12345678 to appear. The log shows: "MobiflightLedModule.Display():Command:SetModule<1.0.0.10000000.0.255>" Does anyone know what this means? Give any clue to know the mistake I'm making? Thank you

Good morning and Merry Christmas to All.
I still have problems with the displays. I have bought a 5v 20A power supply, I have connected it as indicated in the forum (GND connected to the arduino and VCC to the power supply, I use pins CLK 23, CS 25 and CLK 27), I have changed cables, etc. etc When doing the test I can't get 12345678 to appear. The log shows: "MobiflightLedModule.Display():Command:SetModule<1.0.0.10000000.0.255>" Does anyone know what this means? Give any clue to know the mistake I'm making? Thank you

Hi, just to make sure. Have you connected like this?
Power supply VCC to MAX VCC
Power supply GND to Arduino GND to MAX GND. (so the grounds are common for all components)

I have to say that MAXs are VERY sensitive (for cables, for joints, for interferences).
I've also tried external power supply, but at the end the Mega could handle them well.