Displays are messed up (showing numbers that aren't correct/characters that don't exist.

[inner holly]

I've been trying to set up an arduino nano radio panel build and I'm having issues with the displays. I have two MAX7219 6 digit LED displays from PropWash Sim (https://www.propwashsim.com/store/p/7segled) set up daisy-chained (J2 pins from display 1 go to j1 pins from display 2). However, although MF seems to be receiving the proper values from X-Plane 11, the displays aren't showing the correct things. Display 1 shows (with each digit in square brackets) [top segment+bottom segment] [d] [top segment+bottom segment+left top segment] [3.] [3.] [3.] instead of "121000" and Display 2 is showing nothing. Displays are as seen in the picture.
Logs are below.

[elfin urchin]

Start here: https://docs.mobiflight.com/devices/seven-segment-display/troubleshooting/

[inner holly]

What's the best way to run just display 1?

Can I just unplug the second one (without mobiflight program running of course) or will it yell at me for that?

[elfin urchin]

yeah, just unplug it

[inner holly]

Okay

[elfin urchin]

it's not going to be bad chips since those are propwash boards. More likely bad wiring

[inner holly]

Probably bad wiring

I'm running only Display 1 now

Here's what happens

If I try to test or to run the program, it flashes random characters for fractions of a second at a time, then goes dark

The problem could be the wiring

I have some improvised connections to say the least

[elfin urchin]

The page I sent lists the causes. It's always one of the things listed there.

This isn't a software problem

[inner holly]

Some of my Dupont connectors are the good elegoo ones, but all of the ones that are female are crappy thin ones I had laying around

[inner holly]

I thought as much but googling so far hadn't helped

What's the best way to get external 5v power?

[elfin urchin]

old charger for something is common

cut the end off, strip the wires

if it's just one display it won't be the 5v power

it's most likely crappy connections to the data pins

[inner holly]

Hmmm

1 sec

If I'm changing wiring I should unplug the arduino

Yes?

That feels like common sense

[elfin urchin]

you'll need to reset the display once it goes wonky anyway by cutting power to it

I always unplug the arduino so I can do the wiring and stuff away from my PC in a more comfortable setting

[inner holly]

And then just plugging it back in afterward should be fine?

I just had those com port issues I don't want to have to reinstall the device again

[elfin urchin]

should be fine

[inner holly]

Arduino connection is fine

New issue

Mobiflight isn't detecting the displays

Hooray

[elfin urchin]

Mobiflight doesn't "detect" anything. It's whatever you set in the Modules dialog

there's no way for mobiflight to know if a display is actually connected there, or a switch, or whatever. it just sends data out the pins you configured in modules

[inner holly]

Here's what I'm getting

Let me send the log

Discord isn't showing it all, the errors are down at the bottom

[elfin urchin]

When you opened that config file did you get an orphaned serials dialog? It's trying to show the settings for a display connected to a Nano that has a different serial number than the one you have connected.

[inner holly]

I did yeah

I just hit yes

Should I retry and not do that?

[elfin urchin]

You should retry and do what the dialog says. My guess is your serial number got reset when you were dealing with the flashing issues.

Step by step instructions here, although it's for a joystick it doesn't matter. Steps are the same. https://docs.mobiflight.com/game-controllers/winwing/premade-profiles/#acknowledge-the-orphaned-device-warning

[inner holly]

I did remap to the only display serial it gave me and pressed Assign, but then I get that error

[elfin urchin]

make sure you follow the steps exactly. You need to select the orphaned device in the top list first, then select the correct nano in the bottom dropdown.

this isn't about display serials (there is no such thing), it's about your nano

[inner holly]

Okay

1 sec

I select the orphaned serial

And the connected module

Then I press Assign

Orphaned serial disappears

Then I press Ok?

[elfin urchin]

ok to what?

[inner holly]

After I press Assign in the orphaned serials window the serial disappears from the list (making it empty), the drop-down select contains only the one serial it says is attached, and the window stays open

My two options are Ok or Cancel

[elfin urchin]

yeah, exactly. then say ok

then save your file

[inner holly]

Before testing?

[elfin urchin]

yeah, you want to make sure that new serial number is in the file

[inner holly]

Ok

Save in the main window under File or Save in the Extras>Settings>Mobiflight Modules?

Main window toolbar right?

[elfin urchin]

File save

[inner holly]

Saved

Now it's safe to test?

My plan is to go into Edit for the display in the outputs list, then Displays, then Test

Good to go ahead with that now?

[elfin urchin]

sure

your file is matched back up to your nano. you can proceed with futzing with wires to see what's causing garbled data to the displays

I'm going to bed 😅

[inner holly]

Okay

Thanks man I appreciate your help a lot

99% chance I'm gonna be sending more messages but I won't expect support until another day

Have a good night!

New update: Still have the display module not present error

Yippee

Scratch that I had to reupload the module and now it's detected

Still have the weird momentary flash with wrong characters going on

Probably just bad wires

Solder joints are fine if I say so myself

But I think I might try getting more elegoo dupont connectors as well as some pin header strips and solder pin headers to the board for the pins I have the display on so I can easily use the dupont connectors

[inner holly]

@elfin urchin Bringing this back because I finally go around to soldering

I soldered pin headers on the arduino so now I have the dupont connectors to connect the display boards

For context they're MAX7219 6 digit 7-segment displays

Even with more solid connections I'm still having issues with the displays either showing garbled nonsense or flashing the garbled nonsense and then turning off

This is all while trying to test

They should be displaying 100.000

I'm testing with just one board right now

I'm now testing using 5V 1A external power

The display lights up very bright until I try to test through MobiFlight, at which point the display turns off and refuses to show anything else until disconnected and reconnected

Or reset with the button

[elfin urchin]

These same troubleshooting steps still apply, they cover all the reasons why max chips dont display properly

[inner holly]

I've tried all of those.

1. The external 5V power supply worked worse than the onboard 5V of the nano.
2. Just running one display so it is dedicated
3. Using Elegoo Dupont wires
4. N/A
5. Double checked, if the pins are wrong I don't know what I did
6. Trying only one
7. Same problem with both modules
8. My displays are from Propwash Sim and don't have the spot for a decoupling capacitor

[elfin urchin]

post a photo of your soldering

[quasi skiff]

Not having a spot for the decoupling capacitors is just a minor inconvenience. You can always solder through hole parts directly to the VCC and GND, usually located in adjoining holes in the PCB. Does the module at least have the small ceramic 0.1 uf cap?

[twin cloak]

Did-you use test button? depends how use display you flag in my case 5 so I read** 15500** but if you write only 1 you read 10000

be carefull also of Display settings Name number follow the MF tutorial

[inner holly]

Yeah

Thanks for the help and suggestions

I couldn't get the MAX7219 displays to work so I gave up and soldered up some TM1637 displays I had lying around and those work perfectly

If I try to use the MAX displays in the future I may come back here but thanks for now!