Simplified MCDU for Airbus A320 family

This version of the A320 MCDU was inspired by the MCDU-design from Mommel .

As i re-created all files totally new from the scratch (and added some more), it is no longer a remix.
But honestly, without Mommels design my version never would have become reality.

Like all the other models i created for my home cockpit, following rules apply here, too:
- print more, buy less
- all modules /models must be “one independent block”
- despite many other designs i do not use 3 panes (e.g. front, button holder, back) - therefore no backlight - and no professional manufactured PCBs
- As far as possible i use Standard Arduino Mega (no Pro or Mini) and the software "Mobiflight"

Attention, for the MCDU some knowledge about Arduino, Electronics - especially the Multiplexer -  soldering and of course Mobiflight are required.

The main concept

All buttons are soldered on perfboards PCBs and these are fixed with mounting frames from the backside of the panel with self-tapping threaded inserts.
The upper mounting frame also holds the display with its controller.

Simplified means not only that there is no backlight, but also some less important buttons or lights are without any function. These are the buttons above the display, the two long annunciators on the left and right side and of course the Dim/Bright button.

But with some soldering and programming with mobiflight all other buttons are doing their job.

The picture "MCDU Connector Plate" shows how the buttons are connected to the PCB with 5 multiplexer and some other standard parts and from there to a controlling Arduino Mega.

The small portion on the bottom of the plan is needed for switching off the display without confusing Windows.

Windows needs a powered controller to recognize the display as additional screen.

When starting the simulator with the A320 in cold and dark mode the MCDU display has to be off.
On the given display module (see BOM) is a connector on which EN and GND must be connected, to switch off hte backlid of the display.

It must be done with a relay, as the EN pin of the display controller is "potential-free", so either connected to its own GND or open, and therefore can't be connected with the common GND of the Arduino.

On the controlling Arduino the relay-controlling pin reacts on the flag "AC BUS AVAIL".
As long as this flag is "no" or 0, the relay closes the pins EN and GND and the display stays black without confusing Windows as the controller is still powered.

This "inverting" logic must be done, as the flight time will be longer as the standing on ground time and the relay only will be powered as long the plane is not fully powered up.

For displaying the MCDU content on the display, which is connected via HDMI to the computer i highly recommend the brilliant tool MSFS Pop Out Panel Manager. 

As the real MCDU display has approx. 5 inch and a 4:3 ratio it was difficult to find one in Europe (Amazon etc.) for a reasonable price. But no wonder, Ali has them.

When using another size or ratio, the front plate and the upper mounting frame must be adopted accordingly.

Assembling

"Exploded Drawing" shows how are all parts fit together.

The green parts are the TFT and its controller and the blue parts are the 3 PCBs with the buttons.

All parts are printed with PLA.

• Print the front plate and the mounting frames with 15% infill.

• The button files are in Bambu Lab 3MF format and can be printed with two colors, all relevant settings are made.

• Place all button caps from the back into the correct holes of the front plate.

• Then place the bigger PCB with the already soldered buttons on the right position and fix it with the lower mounting frame.

• After that place the upper mounting frame with the 2 small PCBs and the TFT panel and fix it.

• Finally fix the controller holder on the upper frame, mount the controller board to it and that's it

The remaining soldering should be clear when watching "MCDU Connector Plate".
I used flat ribbon cable soldered directly to the buttons with double row headers at the other end, which go to the connector plate. From the connector PCB goes a 10-wire flat to an Arduino controlling the whole thing.

BOM

Self-tapping inserts: https://www.amazon.de/dp/B07QX74XSN
Display: https://de.aliexpress.com/item/1005008129581910.html
Buttons: https://www.amazon.de/dp/B07XWYHPZH
Multiplexer: https://www.amazon.de/dp/B09VXV67DQ