Garmin G3X RS232 Question

[markhensman]

Hi. I have a G3X touch system in an RV8 with a GNX 375 and a G5 for backup. The GDU 460 is connected to the GNX via 2 RS232 wires (Connext and MAPMX). There is also 2 ARINC connections between the GNX and GAD 29. All LRUs are CAN connected. Everything works great.

I’m trying to connect the G5 to the GNX via RS232 but I can’t get MAPMX as an option and therefore no connection. I’m guessing because MAPMX is already being used by the GDU connection? Is there a solution/workaround to get everything working?

Thanks, Mark

 

[asicer]

If everything works great, then what is it you're trying to accomplish? What additional capability do you expect to get by connecting the GNX directly to the G5?

 

[MooneyDriver78]

I would think the G5 would connect to the G3X?

 

[asicer]

I would think the G5 would connect to the G3X?

Me too, hence the question. The GNX is already connected to the G3x via 2xRS232 + 2xARINC429 and the G3x is connected to the G5, so not sure what else is to be gained.

 

[markhensman]

Apologies for not being clear. All works great except for no NAV info presenting on the G5. I can’t get it to connect through RS232 because MAPMX is not available as an option. No connection for NAV info (specifically) is coming through the can bus. G5 needs to connect directly to the navigator for that to work (it seems to me?). Things like altimeter setting and heading work fine on the G5 (from the G3X and CAN?), but NAV info from GNX is missing, it doesn’t get that info via the G3X, the G5 just shows an empty compass rose with a functioning heading bug - no course arrow or deviation bar. That is where my problem is…

 

[will44s]

The install manual shows a single mapmx serial from the navigator being split to the g5 and g3x like this. If the mapmx input format isn't available on g5 it is because the output format on the g5 isn't baud rate compatible.

 

[will44s]

The lack of Mapmx may not be your problem, if the order of Nav sources in the g3 isn't configured right it will present the same problem.

 

[nauga]

I’m trying to connect the G5 to the GNX via RS232 but I can’t get MAPMX as an option and therefore no connection. I’m guessing because MAPMX is already being used by the GDU connection? Is there a solution/workaround to get everything working?

You don't mention any details of the wiring, but MAPMX is not available on all the RS232 ports on the GNX375. I had to juggle the wiring on my 375 to get the right ports to the right places - including MAPMX to a G5. Do you have an install manual for the 375?

Nauga,
pinned

 

[markhensman]

I didn’t realise it it was possible to split the output, I have all the manuals and thought I’d seen everything in them! Thank you, I’m sure that will solve my problem. On the GNX side only ports 1 and 2 can do MAPMX, but it’s either/or, not both. Splitting would be the only way to send the Nav data to both G3X AND G5. I will give that a go and report back. I’m very grateful for the help. Thank you.

 

[nauga]

On the GNX side only ports 1 and 2 can do MAPMX, but it’s either/or, not both. Splitting would be the only way to send the Nav data to both G3X AND G5.

D'oh...You and @will44s are absolutely correct. I just looked at my wiring diagrams and see that I split the signal (a few years ago, in my defense) to get MAPMX to a G5 and Aera 660. Now I remember the frustration when I found out it was either, not both. Sorry for adding to the confusion.

Nauga,
wired

 

[markhensman]

D'oh...You and @will44s are absolutely correct. I just looked at my wiring diagrams and see that I split the signal (a few years ago, in my defense) to get MAPMX to a G5 and Aera 660. Now I remember the frustration when I found out it was either, not both. Sorry for adding to the confusion.

Nauga,
wired

Thanks man, I’ve scratched a hole in my head over this already. I’ve just searched all the Garmin manuals for a reference to splitting the signal and found nothing except for in the case of 2 G5s. I’m sure it will work as @will44s and yourself say it will, makes perfect sense…

 

[will44s]

I'm not a garmin expert but I think the Mapmx to the g5 only provides gps data and not navigation data. This is a substitute to not using an antenna to the g5.
I tested my setup by disabling the rs232 and all the navigation data was still displayed, must be coming thru the arinc connections via can.

Triple check your gad 29 channels in the g3 configuration, also gps needs to be source 1 or it won't work correctly.

 

[markhensman]

I'm not a garmin expert but I think the Mapmx to the g5 only provides gps data and not navigation data. This is a substitute to not using an antenna to the g5.
I tested my setup by disabling the rs232 and all the navigation data was still displayed, must be coming thru the arinc connections via can.

Triple check your gad 29 channels in the g3 configuration, also gps needs to be source 1 or it won't work correctly.

That also makes sense because I don’t have an antenna on the G5. The only antenna is on the GNX. (The course arrow only appears on the G3X when there is GPS signal). It could be that everything is working correctly now as you say, I just need either GPS (via G5 antenna) or MapMX to the G5. I’m not sure how to tell if Nav info is arriving at the G5. There was a tiny magenta bug on the heading tape on the G5. That should be it?

 

[markhensman]

I did the splice and everything is now communicating as it should. Thanks for the help!