G3x Touch and GTR225 communication issue

[Sportquattro]

Evening all,

I have a problem which has us baffled and are hoping you one of you knowledgeable folk can shed some light on the possible solution.


In my aircraft I have a G3X Touch system comprising a 10” GDU, along with a Garmin GTR225 Comm Radio. We recently removed the previous Intercom system and now use the intercom that is in-built to the GTR225. The radio and Intercom all work fine, however since the changes we now can no longer flip-flop the Comm frequency on the G3X touch GDU. I would ask if anyone with knowledge of this sort of stuff can come up with any suggestions as to what the problem could be, the following may be able to help pinpoint the potential issue:

1. Changing the standby frequency on the GTR225 changes it on the G3X GDU as it should do.
2. Flip-flopping the frequency on the GTR225 changes the standby frequency to the active frequency as it should do
3. Changing the standby frequency of the G3X GDU does NOT change it on the GTR225
4. Trying to flip-flop the standby frequency on the G3X GDU to make it active has no effect.
5. The Station name no longer appears under the frequency on the GTR225 whereas it used to
6. The GTR225 is set to communicate with the G3X system via RS232
7. The GTR225 is set to use RS232 and is set for NMEA
8. The G3X is set to use the RS232 on Port 3 at 9600 baud and set as “Garmin VHF COMM” (see below)
9. The COM Radio configuration page in the G3X GDU shows the active frequency (see below)
10. Of note the G3X System does not seem to recognise what radio we have despite it receiving the radio frequencies from the GTR225 and all the CAS alerts sounds working in headsets (see below)

We believe that as the GTR25 is sending frequencies to the G3X GDU and the CAS alerts etc are all working fine and are audible in headset that clearly there must be some sort of communication between the G3X GDU and the GTR225, however the fact the G3X system does not seem to identify what specific radio we have and the inability to send frequencies from GDU to GTR225 suggest some sort of configuration issue rather than a wiring issue but we are stumped as to what.


Any suggestions to what could be the issue, that would be much appreciated.


Nige

 

[mburch]

I would investigate the RS-232 connection from the GDU (out) to the GTR (in).

 

[JDA_BTR]

I have rev AQ of the G3X installation manual, which is not recent. But on page 35-153 there is a table that describes your situation as the GTR-255 not having the software version 2.10 or higher. So maybe look and confirm that your GTR-255 is version 2.1 or higher. Then of course make sure the radio RS232 speed is set the same as the G3X, and so forth -> but that's prob okay since you can send the freq from radio -> G3X.

The manual also says: "
On-screen com radio control is supported by the following RS-232 formats: Garmin VHF Comm, Garmin VHF Nav/Com, and MapMX. The specific radio functionality that can be controlled using an RS-232 connection depends on the features supported by the software version used by the com radio"

You said your radio was set to NMEA? That isn't one of these three formats....?

 

[JDA_BTR]

I looked in my GTR-225 install manual and it does show NMEA as your best choice on the unit.... so verifying the software version is the best offer I have for you.

 

[Sportquattro]

I looked in my GTR-225 install manual and it does show NMEA as your best choice on the unit.... so verifying the software version is the best offer I have for you.

Yes the software is version 2.10 what baffles us is that everything seems to work bar the flip flop from G3X to the radio, and that the G3X doesn't identify what radio we have. I have emailed Garmin G3xpert and await their reply, hopefully soon. Really hoping its configuration not wiring issue.

 

[HarryL]

I would suggest you check that Pin 16 (RS232 IN) on P2001 of the GTR225 is in fact connecte to the GDU. Sounds like the wire may have broken or pin pushed back during your intercom changes.