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GARMIN Interconnect Question

JDA_BTR

Well Known Member
I'm looking at the following components:
GTN 625 with separate GNC 255 COM/NAV
GDU 460/470 (one each)
G5

Looking through the drawings, the GNC 255 has one serial port to communicate with the rest of the system; I suppose it should be connected to the primary GDU? The drawings show a choice of any of the GPS-enabled items having a potential link to the radio. Is one the best?

Also, for the NAV side of the GNC 255.... Does the 460 or 470 have the ability to show DME, ILS/VOR, etc? How is the NAV radio data read back to the G3X system for use inflight? I think that it may not, but wanted to ask.... is the only way to get this done with a GTN650 having built in Nav/Com and more serial channels?

I see in the G5 docs that the VOR heading can be set with the G5 via a serial link, so I assume the same is true if the serial link is taken to the GDU 460 instead. That also implies the radio will send the VOR error for display back to the G5 or GDU 460 accordingly. Does that also apply for ILS? DME?
 
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I'm looking at the following components:
GTN 625 with separate GNC 255 COM/NAV
GDU 460/470 (one each)
G5

Looking through the drawings, the GNC 255 has one serial port to communicate with the rest of the system; I suppose it should be connected to the primary GDU? The drawings show a choice of any of the GPS-enabled items having a potential link to the radio. Is one the best?

Also, for the NAV side of the GNC 255.... Does the 460 or 470 have the ability to show DME, ILS/VOR, etc? How is the NAV radio data read back to the G3X system for use inflight? I think that it may not, but wanted to ask.... is the only way to get this done with a GTN650 having built in Nav/Com and more serial channels?

I see in the G5 docs that the VOR heading can be set with the G5 via a serial link, so I assume the same is true if the serial link is taken to the GDU 460 instead. That also implies the radio will send the VOR error for display back to the G5 or GDU 460 accordingly. Does that also apply for ILS? DME?

I think you're going to need a GAD 29 arinc box to port the nav functions of the GNC 255 to the G3X system. The G5 communicates over the CANBus in a G3X system.
 
Hello,

The GNC 255 doesn't need an A429 connection to provide VOR/ILS navigation to a G3X system including course selection on the PFD.

Just connect a single serial port connection from the GNC 255 to your PFD as shown on page 26-15 of the Rev. AB G3X Installation Manual.

We recommend you connect the MapMX serial interface from the much higher capability GTN 625 to the G5 serial port input like shown on page 62 of the Rev. C G5 Installation manual. Note that this same GTN serial output is also connected to the PFD.

With this installation, you could turn off both the GDU 460/470 displays and still fly an autopilot coupled LPV approach with the GTN 625 and G5, and of course fly an autopilot coupled flight plan entered on the GTN anywhere you like.

Thanks,
Steve
 
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Hello,

The GNC 255 doesn't need an A429 connection to provide VOR/ILS navigation to a G3X system including course selection on the PFD.

Just connect a single serial port connection from the GNC 255 to your PFD as shown on page 26-15 of the Rev. AB G3X Installation Manual.

We recommend you connect the MapMX serial interface from the much higher capability GTN 625 to the G5 serial port input like shown on page 62 of the Rev. C G5 Installation manual. Note that this same GTN serial output is also connected to the PFD.

With this installation, you could turn off both the GDU 460/470 displays and still fly an autopilot coupled LPV approach with the GTN 625 and G5, and of course fly an autopilot coupled flight plan entered on the GTN anywhere you like.

Thanks,
Steve

Steve, does he still need the GAD 29 for the GTN? Can he push frequencies from the G3X to the GNC 255?
 
Steve, does he still need the GAD 29 for the GTN? Can he push frequencies from the G3X to the GNC 255?

Hello Charley,

Yes and Yes.

Page 34-128 of the Rev. AB G3X Installation manual explains the radio tuning support provided for the GNC 255, and it is quite extensive and integrated for a G3X Touch system.

Thanks,
Steve
 
What is the difference between the MAPMX format 1, MAPMX Format 2, and CONNEXT?

When the drawings are compared between different install manuals, the serial ports overlap in the examples. You've mentioned one instance where the GTN serial port feeds both a GDU (I have two) and the G5 on the same MAPMX (format 1?) output.

After wiring the GNC 255 to the primary GDU, I look at the example page 26-26 in the G3X installation and see the same primary GDU serial port called out for a GDU-GTN interface withe same serial port as called out for the GNC 255.

I suppose I can just tailor the docs to change the serial ports to accommodate everything but it would be super helpful if the documentation put some choices in it so a lot of cross-reference wasn't needed.

Are there other places (like the GTN->GDU/G5) serial link where one serial output feeds multiple inputs?
 
On further review....

On the drawing for my PFD (GDU 460), I am finding that I need:
Ser1 -> GTX 45R for ADSB data
Ser2 -> Nav/Com from GNC 255
Ser3 -> CONNEXT from GTN 625
Ser4 -> MapMX from GTN 625 (625 also sends this to G4 SerRx same signal)

I also have a GDU 470 in my plan. Each GDU has 5 serial ports.
The CO detector needs one. Should it go to the second GDU?
What else?

Looking at the Fig 2-2 page 2-3 of Rev AB G3X install, I need RS-232 from GDU to GMC 307. Haven't found that elsewhere in the docs yet

And yes, I am working with Stein to put in a panel but even if he gives me a nice drawing I want to know how it all connects up so I understand it. I also want to make sure I get every feature included..... I'm planning to wire it myself.
 
What is the difference between the MAPMX format 1, MAPMX Format 2, and CONNEXT?

When the drawings are compared between different install manuals, the serial ports overlap in the examples. You've mentioned one instance where the GTN serial port feeds both a GDU (I have two) and the G5 on the same MAPMX (format 1?) output.

After wiring the GNC 255 to the primary GDU, I look at the example page 26-26 in the G3X installation and see the same primary GDU serial port called out for a GDU-GTN interface withe same serial port as called out for the GNC 255.

I suppose I can just tailor the docs to change the serial ports to accommodate everything but it would be super helpful if the documentation put some choices in it so a lot of cross-reference wasn't needed.

Are there other places (like the GTN->GDU/G5) serial link where one serial output feeds multiple inputs?

Hello JDA_BTR,

Yes, the installation manuals show one example of a serial port connection from one device (like the GNC 255) to a display, but don't show all possible combinations.

The first 5 serial ports on each of your GDU 460/470 displays can each be configured to connect to a wide array of devices such as GMC 305/307, SL30, SL40, GTR225, GNC255, GDL39/39R, GNS/GTN navigators, TIS traffic devices, GTX 45R/345 ADS-B receivers, third party autopilots, GTS 8XX active traffic system, GEA24 and GSU25 backup data buses, electronic circuit breaker, CO detector, lightning detector, and more. It wouldn't be possible for us to show all of these connections and never "overlap" in the example wiring diagrams.

The 6th serial port on each of your displays is on the P4601 and P4701 9 pin connector and is always configured to be a backup data bus for the GEA24 and GSU25 as shown on page 25-18.

For your system the GTN 625 serial port connected to the PFD and G5 is configured for MapMX Format 2 as explained on page 26-26. We would use a separate serial port on the GTN to provide a dedicated connection to the G5, but the GTN only allows one serial port to be configured for MapMX Format 2, so the transmit line on that GTN serial port is connected to the serial port input on both the PFD and the G5. This is the only serial port in your system for which a serial port is connected to two places.

Your CO detector may be wired to either GDU.

Oh, and we do have email and telephone customer support (see below) anytime you need to discuss specifics for your system.

Thanks,
Steve
 
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CONNEXT...
If I have a GTN625 with no Com/Nav, is a serial connection for CONNEXT needed to the PFD or MFD? If needed, which is best?
 
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Different drawings show different things too.

Should the GSU25 backup serial port go to the PFD, or the GTX45R? Seems the GTX is a better choice since that keeps ADSB going even on a CAN bus or PFD failure? The GTX would be getting GPS via ethernet in that mode still.

Should a serial GTN->GTX link be provided for backup even when an ethernet is cabled in?
 
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CONNEXT...
If I have a GTN625 with no Com/Nav, is a serial connection for CONNEXT needed to the PFD or MFD? If needed, which is best?

Hello JDA_BTR,

Yes, the Connext interface shown between PFD1 and the GTN on page 26-26 of the Rev. AB G3X Installation Manual is needed for the GTN 625 if you want to be able to push flight plans from the PFD1 display or from an external portable device Bluetooth connected to PFD1 to the GTN.

This is purely an optional feature and not needed to use the GTN and fly IFR if you don't want to install this RS-232 connection.

Thanks,
Steve
 
Different drawings show different things too.

Should the GSU25 backup serial port go to the PFD, or the GTX45R? Seems the GTX is a better choice since that keeps ADSB going even on a CAN bus or PFD failure? The GTX would be getting GPS via ethernet in that mode still.

Should a serial GTN->GTX link be provided for backup even when an ethernet is cabled in?

Hello JDA_BTR,

The GSU 25 ADAHRS to GTX 45R transponder interface is a single RS-232 interface and is shown on page 26-22 of the Rev. AB installation manual. This interface has absolutely nothing to do with a GSU 25 backup data path.

The GSU 25 RS-232 backup data path to a display (PFD1 recommended) is shown on page 26-9. There is no such thing as a GSU 25 backup data path to a GTX.

The Ethernet interface between the GTN and GTX 45R shown on page 26-22 is a bi-directional link that both provides ADS-B+ data to the GTX 45R enabling it to provide ADS-B Out and provides ADS-B traffic/weather data from the GTX 45R to the GTN.

We don't recommend both the Ethernet interface and an RS-232 interface to get GPS data from the GTN to the GTX and haven't tested that, but it might work.

Just follow those two wiring diagrams on those two pages and you can't go wrong.

Thanks,
Steve
 
Hello,

The GNC 255 doesn't need an A429 connection to provide VOR/ILS navigation to a G3X system including course selection on the PFD.

Just connect a single serial port connection from the GNC 255 to your PFD as shown on page 26-15 of the Rev. AB G3X Installation Manual.

We recommend you connect the MapMX serial interface from the much higher capability GTN 625 to the G5 serial port input like shown on page 62 of the Rev. C G5 Installation manual. Note that this same GTN serial output is also connected to the PFD.

With this installation, you could turn off both the GDU 460/470 displays and still fly an autopilot coupled LPV approach with the GTN 625 and G5, and of course fly an autopilot coupled flight plan entered on the GTN anywhere you like.

Thanks,
Steve

Dear Steve. I need to connect a GNC 255 to G3X GDU 460, I cannot find page 26-15 of the Manual. Is there any installation guide or manual for this interconnection ? Thanks !
Maximo.
 
Dear Steve. I need to connect a GNC 255 to G3X GDU 460, I cannot find page 26-15 of the Manual. Is there any installation guide or manual for this interconnection ? Thanks !
Maximo.

Maximo,

See page 27-25 of the current Rev. AP G3X Touch Installation Manual.

Steve
 
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