MobiFlight Community Support

Hi, I have some 8 digit Max7219 modules, however they are not working correctly.
When I plug them in they show 88888888 and when I open Mobiflight, the lights go out.
I have the pins configured correctly and in the config I have my digits and decimal point set as I want it. When I press test, sometimes it shows 123. and sometimes nothing, sometimes something random.
When I have the sim running it shows that the output should be 12135 (so it shouldn't be a sim problem), but the display shows nothing. I also tested this with another arduino and another led module, but so far I didn't get it to work correctly!

This is a Hardware Problem...... Located on the MAX side.

Mostly the premade 8Dig Displays are verry poor. Maybe 2 of 5 are not working when deliver. But not get scarred..... they are not "broke".... they only have bad solder points!

The Max is verry sensible.... And in case it must be initialised at startup of the Mega it not work anymore if there is a Issue in the electrical part later..... means you need to Restart the MEGA and also Mobiflight to "initialise" it once again!


Solution:

1. All Wire work and connections must be 100% accurate ! Never use Jumper wires or Breadboard experimental setups.... SOLDER every single connection. Doublecheck the solder Points are PERFECT !
Already touching of the Panle Box can be enough to crash the system aslong just one single wire have a little wriggle Contact !

2. Rework the Premade Tubes before you sue them.... Means you have to resolder the 5 Contacts ( where Male Pins are set) .... Get sure each solder point goes through the hole.... And no Solder touch one oth the other 4 Solders......
NOTE: For a 1 Max Chain only the LEFT Contacts are important..... For a Chain with 2 or more Max Modules ALSO the Right Contacts must be working perfectly !

3. Get sure the Display was connected already BEFORE you startup the Mega ( Connect to USB and power it) .
Its not possible to connect a Max7219 after Mega is already running ! Then a Restart is needed !

Okay, I will resolder the board and hardwire the connections to the arduino. I hope this works
I'll keep you posted!

So I did as you said and soldered the connections.You weren't joking when you said every connection has to be soldered; I even had to solder the power connection directly to my Arduino!

For the sake of other newcomers to Mobiflight, please state in the Tutorial for the 7-segment-display that the connections must be soldered.
But anyways, thank you for your quick reply and help

One more thing to remember with Max7219 modules if you daisy-chain them. Typically there is a diode in the power line protecting against a reverse connection. So with daisy-chained modules the next one in the chain is getting about 0.7 Volts less supply voltage than the previous one. You need either to short every diode or to connect power to each of the modules directly from Arduino.