These are similar to the widely available 7segment modules. but with two differences:

• There is no reverse voltage protection diode, so there is no voltage drop, if you chain the power as well, but of course if you accidentally connect the power wires backwards, you will likely destroy the MAX7219 chip.
• The larger modules contain two MAX7219 chips, so there are two chained displays in one, enabling you to have more than 8 digits (the 10 and 12 digit boards to build a radio panel with just one module.

To connect these to MobiFlight, connect the DIN side to your arduino and pay careful attention to the GND and 5V wires, so that they are connected properly, the DIN/CS/CLK pins (circled in yellow) can be connected to any Arduino digital pins that you can then select in the device configuration in MobiFlight:

If you have one of those modules that have two MAX chips in the board like on the above photo, select the "Num" setting to 2.

Several MAX7219 modules can be connected together and they can then share the data pins. To do so, connect the first one using the DIN connector, and then connect the second module to the DOUT connector (not circled in yellow) and set the correct number of MAX chips. Note that in the PropWash modules that have two MAX chips, one module naturally counts as two. So to chain two of these together, you would set the Num to 4. Or 6 if you chain three, and so on.

When chaining, you will need to use a separate 5V power supply for the 7segments, as the Arduino is not able to power more than one reliably. In this case, power the modules from the power supply 5V line, and connect the power supply GND and Arduino GND wires together.

These modules also have the first digit wired on the left edge, as opposed to having the first digit be the rightmost one. Thus you need to use the "reverse digits" option in MobiFlight device configuration.

In the above example, I have configured the 10 difit (5+5) display, so I have selected the "reverse digits" option, as well as checked the display digits 1,2,3,4 and 5 to be active.