EFIS Panel Unit

My EFIS Panel Unit

When I talked about the MCP I called in the most complex panel unit. Well the EFIS is equally densely populated.

Before I introduce the EFIS panel unit, be sure you understand FSIO panel hardware.

If you build the MCP, you already know.

The problem for most of us is the availability of (cheap, but miniature) components. So I settle for better available larger components. Making it all on one print proved to be almost impossible using through-hole components. Sure, if one uses miniature rotary switches and SMD, one would be able to make it on a single PCB.

The schematics.

The schematics is 2 parts.

The lower PCB witch has all the components and connectors. The TOP PCB  only had the PUSH buttons.

Lower PCB.


The schematics of the top board is not all that exciting, but here it is.

If you are familiar with the FSIO Panel Hardware this schematics should not come as a surprise. A few things I point out:

  • Position 0 of the rotary switches are not connected. Your script will have to detect that NO-connections means 0 (“zero”) position.
  • You will see a connector SV4 (in fact 2 rows) that will connect to the top board for the buttons.
  • The drawing in some places is a little messy. This is because I designed the boards in a way, that it can be home-made (no trough-hole plating). Therefore, I needed to make sure, that all the connections to the switches and connectors can be soldered from the solder side of the board.
    Later Sebastian decided to have the boards professionally built. As soldering is not an issue anymore, some changes were made that defer from the home build principle.
  • I did not have a solution in mind for the TFC and CTR pushbuttons. I either think of drilling a hole through the rotary switch shaft of 3d print the knob with a micro switch in it and a small wire to connect.
  • For the STD and RST pushbuttons, it is part of the rotary encoder with pushbutton.
  • A rotary encoder with double shaft with switch and pushbutton is hard to get and hard to pay for, so we have to be creative.
    The MINS RADIO-BARO selector and the BARO IN-HPA selector – I choose for miniature switches here. In the prototype they stick out a bit through the front panel, but there is a lever that is connected to the knob behind the front panel. So, in a final version I will cut-out part of the of the switch ‘lever’, so it will not be visible anymore. I will show it below.
  • I had to sacrifice the FPV button. It is available on the top board, but I would need an extra input chip to facilitate this button (1 input) that on many planes is INOP.

The bottom board with some hardware placed before soldering.




The top board schematics is simple. It has 2 rows of 5 pin in-line connectors to connect it to the bottom board.

  • The front panel + all the knobs were made on my 3d printer. Just to show the measurements etc. It will be replaced by proper panelling at a later time.
  • In my box of components I had some pushbuttons with green LED. So my idea was to use these to allow an indicator (or backlight) to the buttons. These buttons do not have indicators, so you would not need the LED (except if you want a backlight).
  • The top board is held in place by the nuts of the rotary switches.
  • The MINS RADIO-BARO switch and the BADO IN-HPA switch is directly soldered on the lower board to go as low as possible.
  • The VOR/ADF switches are mounted as high as possible, they are fastened to the top board highest position. This means that you first fix them on the top PCB. Solder some solid wire on the pins. Then put the board on top and solder the short wire to the board. You can the losen the scews and you will be able to get the top PCB lose again to do some more work etc.

I will copy the eagle files in the hardware section of the forum. With all these files, NO GUARANTEE. You need to understand and check, check and re-check yourself.

One problem we know is with the lower board. The connectors to CPU and next panel unit are on the front side of the board. This happened just after the last review before sending the files to the manufacturer. The connectors should be on the bottom side for easier access. Now one needs to remember to connect the cables before the top board is placed and fixed on the botton board. If you have to do it once, it is nor realy a big problem, but this makes my point of check, check and re-check…

Top PCB placed and fixed. See the VOR/ADF are fixed to the top PCB as wel as the rotary switches.


The picture below shows how I created the knob to toggle the MINS RADIO/BARO and BARO IN/HPA switches. The knob is fastened to the notch exersizing the switch.


The prototype with 3d printed panels, knobs and buttons. I must have had too much green filament. Well, some day we will be able to lasercut nice front panels.


EFIS Connected

FSIO architecture allows Panel Units to be chained to a single CPU board.

This is exactly what I did.

In the downloads I will put a new SIOC script with EFIS script added.

I had to connect the EFIS first and behind that the existing MCP.

Yes, I had to adopt the MCP part of the script. This would not have been the case, if I had left the MCP first in chain and the EFIS second. As the MCP prototype hardware CPU connector has a little error (corrected in the final design), I had to make a special connection-cable. I woud have to make more special cables to connect the EFIS after the MCP. Much easier to change the script, isn’t it?

That is all I can write about it now. If you miss anything or find something unclear, drop me a line.


Thanks again for all the support and work done by Sebastian from Poland. He keeps me enthusiastic, checks and re-checks my work, makes the PCB’s etc.

Without him this site would not progress as it does.


PCB’s for this unit are available My First Boeing shop