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NexGen RSS Continued.. Hacking the Gables G1981 ATC Panel --The Protocols III

phoenixcomm

Remember when I was talking about Protocols and the RSS? Well then this will fit right in.image

 

The Analysis: First we have to find all of the I/O in the Gables G-1981 ATC Transponder Panel and find out what they do. First a little background about ATC Transponders:

"is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on radar. Air traffic control towers use the term squawk when they are assigning an aircraft a transponder code,  Squawk 7421"

 

The code is 4 octal numbers. What's octal? Octal is 0 through 7 coded in 3 bits. So 4 octal numbers = 12 bits.

Function SwitchPositionsBits
Function Switch42
Mode Switch42
ATC TR Switch21
Test / Monitor Switch32
ALT Switch33
Code Switches x 47 x 412
IDENT21
Panel Lamps

Dial Lamps

Monitor Lamp

Total Bits Needed:23

So now we have all of the outputs.

The inputs are much easier you only have: panel lamps, dial lamps, and the Monitor lamp.

 

The Plan: is really two parts:

Plan what embedded microprocessor to use. And for a change its really a no brainier. I am going to use a Arduino Mega as it has lots of I/O.

A) Design both sides of the protocol.

The output of the Arduino is 23 packed bits, +1 bit for packing  giving me 3 packed Bytes plus house keeping of 1 Start Byte, plus one Radio_ID Byte, making the total of 5 Bytes.

A.1) Write to Arduino to the IOP.

A.2) Write from the IOP to the Arduino

A.3) Write the Linux driver in the IOP

A.4) Write the Linux IOP to the Arduino.

B) Test in stages.

B.1) Use the serial monitor to see outbound traffic from the Arduino

B.2) All of the ATC head inputs must come from the Interface Card as it requires 5vdc for the various lamps.

B.3) Make sure that the ATC Transponder does not need to be hacked. If so note it and fix it.

B.4) Now I can build the I/O Cable.

B.5) Install into the RSS and verify that every switch is functioning properly.

C) Go Flying!

 

image Keep Tuned In More To Come

Cris H~

 

BTW I wish to thank the folks a Gables Engineering for there great support and documentation of the various control heads that we are using.

 

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  • Hi Christine,

     

    How are you handling the transponder internal events?

    Are you using the switches to set up the simulation only?

     

    You can usually get the cables at surplus stores or from aviation recycle facilities.

    You might be able to buy them, but they are usually expensive.

    I built some test rigs where we just bought the commercial connector and wired them up.  That way you can make sure that the other end is compatible with your hardware.

     

    Keep up the good posts,

    DAB

  • in reply to DAB

    Dab's 3 questions:

    1. transponder events.. what do consider internal events?

     

    2. All the switches are installed ie. when finished this box will look and feel like the real thing...

     

    3. Cables I normaly roll my own.. I normally buy new surplus connectors from a company that sells them commercially. But they give me a "good deal" as I also sell connectors to them as well. some times I get lucky and get the right shell that has been used sometimes.. so if its a solder tail well its work and if its and insertion pin connector I have to get the pin tool and pins from them. Also I also look for the plastic version of the connector as well I can drastically drop the price by more than half.

    The one end is a Bendix/Canon plug and the other normal goes to a IDC connector 50pin for signals and a Molex plug for panel lamps.

    I used to buy connectors from the Dallas First Staterday.. but for the most part they have dryed up as these A-holes destroyed the surplus new connectors by taking the pin kit and using it for GOLD SCRAP image Crap I used to  pay 5 to 10 cents a pin for the most part.. and that was at 800 dollar Gold.

     

    Some folks like to use screw or fast-ons but that seems to me just a waste of time there good for testing.. like my pin boxes.. but not in the long run..

     

    Enjoy

    Cris

  • in reply to phoenixcomm

    Are you not going to support mode S then?

     

    I can respect why you might not, given it's more complex and involves passing quite a few more bits around - but I thought it worth asking.

  • in reply to Dudley

    I think that this panel supports mode S but I'm not sure.. and I don't know how the alt is reported in the bit stream ( not too worried about that though) this unit was used on 707, 727, 737, and was used on a Collins 621A3 Transponder. If you have any info about the transponder or the controls please be forth comming... Thanks

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  • in reply to Dudley

    I think that this panel supports mode S but I'm not sure.. and I don't know how the alt is reported in the bit stream ( not too worried about that though) this unit was used on 707, 727, 737, and was used on a Collins 621A3 Transponder. If you have any info about the transponder or the controls please be forth comming... Thanks

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