No Mode C

[rv7alamb@sasktel.n]

My RV7A is equipped with a single Skyview screen and four Garmins; a GTX 327 transponder, a SL30 nav/comm, a GMA 340 audio panel and a GDU 370 GPS. I have 20 hours on the aircraft and only have one outstanding snag. I can’t get the GTX 327 to show a mode C altitude. I am fairly certain the Dynon Encoder Converter is wired correctly. I tried every combination I can think of setting up the serial ports. Have I missed the right combination? Is there something else?
Thank you
David Lamb

 

[dynonsupport]

Do you actually have a Dynon converter between the SkyView and the 327? You don't need one, and it's a lot easier to wire and troubleshoot the single wire connection without the converter than it is to deal with the 15 wires you need with the converter.

 

[rv7alamb@sasktel.n]

I think in answer to your first question the answer is Yes.
I am not too sure what you mean when you say “you don’t need one?”
I have the Dynon Converter wired into Serial Port 1 on the SkyView display DB37 as per revision K - Figure 85–Encoder Converter Module Electrical Connections on page 14-12. I then configured Serial Port 1 as per the instructions immediately below Figure 85.
SERIAL # IN DEVICE: NONE
SERIAL # IN FUNCTION: NONE
SERIAL # IN/OUT BAUD RATE: 1200
SERIAL # OUT DEVICE: DYNON CONVERTER

The GTX327 is wired into Serial port 4 - Port 4 RX to GTX pin 20 and Port 4 TX to GTX pin 19. This, I think, complies with the wiring info available? What I am not too sure of is the setup for the GTX Serial Port? I have tried a number of iterations and can’t seem to get anything to work.

SERIAL # IN DEVICE: ?
SERIAL # IN FUNCTION: ?
SERIAL # IN/OUT BAUD RATE: ?
SERIAL # OUT DEVICE: ?

Is there another way to wire it all that I missed? I hate the thought of tearing my panel apart to get in and rewire! Is there a configuration that will work the way it is currently wired?
Thanks
David Lamb

 

[Brantel]

Yeah, what you missed is that with a G327, you don't need the Dynon converter at all. And more importantly, you don't need both the Dynon converter connecting the EFIS to the 327 and another serial connection between them. You only need one or the other.

The suggestion is to only use the serial connection when you have a transponder that talks serial. With this single connection, the transponder can get everything it needs from the EFIS.

I would go thru the pain to get it wired correctly.

 

[mmarien]

You need to get rid of the converter and all the wiring (pins 3-12) except:

SV Port 4 TX (pin 10) to GTX327 pin 19 and SV Port 4 RX (pin 9) to GTX327 Pin 20. GTX Pin 25 should connect to a SV GND wire. See figure C2 in the GTX327 manual and pretend that the GNS480 is Skyview. Ignore all the pins below that on the diagram. On the Skyview setup Port 4 for Icarus out. I think you have a choice of Icarus 10ft or Icarus 100ft.

If you want the transponder to display on the Skyview top line, then set the GTX327 serial port 1 to REMOTE. On the Skyview I think you can pick the GTX327 IN on port 4.

The only other wires on the GTX327 besides pin 19 and 20 is pin 15 connected to power and pin 13 should be grounded. If you connect GTX327 Pin 1 and 15 to the same power, the GTX327 will come on when you apply power.

See this post: http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1311029115

 

[rv7alamb@sasktel.n]

Hi Murry,

Thank you very much for your input. I just came from the airport. I changed the appropriate settings in the SkyView and the GTX 327 and all indicators are that I have resolved the problem. The wiring I have done with the Encoder includes all the settings you described so I think I'm OK.
The weather looks like it is clearing up and I should be able to go flying this afternoon. Hopefully all is well!
Thanks again
David

 

[rv7alamb@sasktel.n]

Thanks again to everyone. I went flying today and the Mode C is working fine.

Warmest Regards
David Lamb

 

[mmarien]

Good work. Happy flying. See you at CRF5 some Sunday for breakfast.