ARINC429 Anyone?

[RayS]

I'm working on reverse-engineering a Rockwell-Collins CTL-92 Transponder. It uses the ARINC429 protocol, standardized by Rockwell-Collins.

I have a situation that I've not seen before:
I have a ARINC429 Development Kit by Holt Integrated. When I start it, I can see the dual-comb +5/-5vdc output and it looks normal.

When I put a scope on the output of the Transponder, I can see the output, but it looks nothing like your typical ARINC429 output. It's a 0/+5vdc square wave output, and I can watch the square wave change as I set values and switches on the radio.

It's almost as if the square-wave output hasn't yet been converted to a true ARINC429 signal. It actually looks like bit-bashing and I'm wondering if I'm missing something here...

Is anyone here familiar with ARINC429? And more importantly, can anyone help... :-)

I'm hoping I'm just missing something simple, like I'm using the wrong output pins on the rear cannon plug. (I triple-checked it and I am using the 2 Data Out pins.)

The spiky image on the left is the output from a Holt ARINC429 transceiver chip, the square wave image is the R/C Transponder output.


 

[mickc]

Definitely doesn't look like ARINC coming out of the unit, there's no low side on the waveform. 
Sure its not some strange proprietary data format from RC?  I cam across that when interfacing my RMI

[Ryan]

Ray,

Collins uses CSDB (Commercial Standard Digital Bus) in many of it's older tuning units. My CTL-4210's have inputs for older CSDB transmitters so it got me thinking - maybe that is what your seeing out of the CLT-92.

If we walk the installation a bit consider this - the CTL-92 is used to tune the TDR-94/94D transponder.  I found the maintenance manual for the TDR-94 in a PDF sent it to your email.

In that manual, is this gem on page 58:

TDR-94 with CSDB Code Selection
(a) Figure 16/GRAPHIC 34-50-96-99B-083-A01 shows a TDR 94 installation with a CTL 92/92A CSDB transponder control unit and an altitude encoder.

I sent you a manual for the CSDB standard - it's a square wave, burst output single between +3.0v and +5.0v.

I think you're looking at CSDB out of that CTL-92 tuning unit.

Good luck,
Ryan

[jskibo]

I always get confused reading these posts by you scientists

[archen]

I always get confused reading these posts by you scientists

Haha me too [emoji16]

Skickat från min LYA-L29 via Tapatalk

[bernard S]

mick   .. your software re RMI   was it sending the signals to unit   and unit sending signals to needles   or was software sending signals to needles ?

[mickc]

mick   .. your software re RMI   was it sending the signals to unit   and unit sending signals to needles   or was software sending signals to needles ?

Software sends the Arinc label & data to the interface board, and the board compiles it into the correct bit format, and sends it onto the RMI.
The board has 1 High Speed A429 and 2 low speed A429 transmitters.  HS is for the heading info, and the 2x LS buses are for the ADF/VOR bearing info. ADF1 & VOR1 share a bus, as do ADF2 & VOR2.
The waveform is the A & B channels for the High Speed bus.
Everything else is done by discretes, so the heading system is not operation until the left IRS is aligned etc, and the system can be switched to the right IRS if needed using the switch on the overhead like the real deal

[RayS]

Thanks everyone for your input. Now to find anything on CSDB and microcontrollers....

Ugh... I should have taken up underwater basket-weaving........

[mickc]

Ugh... I should have taken up underwater basket-weaving........

Completely understand where you are coming from.
One step forwards, then 3 backwards and 2 sideways

[bernard S]

mick   .. your software re RMI   was it sending the signals to unit   and unit sending signals to needles   or was software sending signals to needles ?

Software sends the Arinc label & data to the interface board, and the board compiles it into the correct bit format, and sends it onto the RMI.
The board has 1 High Speed A429 and 2 low speed A429 transmitters.  HS is for the heading info, and the 2x LS buses are for the ADF/VOR bearing info. ADF1 & VOR1 share a bus, as do ADF2 & VOR2.
The waveform is the A & B channels for the High Speed bus.
Everything else is done by discretes, so the heading system is not operation until the left IRS is aligned etc, and the system can be switched to the right IRS if needed using the switch on the overhead like the real deal

[bernard S]

i know that bit   i meant the core sim software

[mickc]

i know that bit   i meant the core sim software

P3D just sends the heading and navaid relative bearing variables which are extracted from Simconnect, and the Arinc board software turns it into A429 labels and data. Its a small exe that runs alongside the sim itself.

[kattz]

May I please join this conversation?

Just a question -

In my sim, I will (probably) only have four items to run ARINC429 for.  IRDU, chronometers x 2, RMI.

What is the best way to learn about ARINC?

Cheers.

Kev

[mickc]

May I please join this conversation?

Just a question -

In my sim, I will (probably) only have four items to run ARINC429 for.  IRDU, chronometers x 2, RMI.

What is the best way to learn about ARINC?

Cheers.

Kev

Start here

[kattz]

Thanks, Mick!