Gemini position?

[FlyPig]

Hello,

I've been back and forth with Mid-Continent and Garmin about my TruTrak Gemini (Bendix King xCruze 110) autopilot. It worked fine with only a single RS-232 wire from a Garmin 496...before my ongoing upgrade.

Now, with a Garmin GPS175 feeding it both ARINC427 (directly or through a GAD29) and RS232 directly, the Gemini appears to be happy with the GPSS solution it gets, but never "finds itself".

The GPS status of the autopilot DG never changes from red , no matter how I set the GPS out signal. I've also tried to give it an RS232 GPS signal from a GPS 20A, also to no avail. The manual says this indicates the unit isn't receiving a valid GPS signal.

The consensus with Garmin and BK (Mid Cont) is that this autopilot MUST have a 9600 baud RS232 signal and that the newer generation GPSs don't communicate this slowly.

What's the brain trust say? Thanks in advance!

Chris
2010 RV-7

 

[mburch]

Not sure what a Garmin GAD 29 would have to do with a Trutrak Gemini instrument, but your GPS 175 can certainly provide Aviation format data at the standard 9600 baud rate if you configure it to do so.

 

[BobTurner]

Hello,

The consensus with Garmin and BK (Mid Cont) is that this autopilot MUST have a 9600 baud RS232 signal and that the newer generation GPSs don't communicate this slowly.

What's the brain trust say? Thanks in advance!

Chris
2010 RV-7

On your GPS175 you have to configure the RS232out port you’re using to send data to the autopilot. Does it say ‘9600 baud rate’? If so then that’s not your problem. You also need to configure the ‘format’. Again, what does it say (NMEA, Aviation, etc). Is this listed as a format the autopilot can read?

 

[Longez]

Configuration for connecting a GPS 175 to a Gemini (xCruze 110) autopilot is a simple two step process.

GPS 175
Configure the RS -232 output connected to the Gemini to "Aviation Output 1". The GPS 175 automatically configures the baud rate to 9600 baud.

Gemini
Set the baud rate of the RS-232 input port to 9600 baud. As explained in the Gemini installation manual, it automatically recognizes and uses the Aviation output data from the GPS 175 when the baud rate is properly set.



If it still doesn't work, then check the RS-232 interface wiring.

Steve

 

[uk_figs]

Not sure I quite understand your situation (as you say you have both rs232 and arinc429 form the 175 to the gemini) but I have the gemini connected to a GNX375 (same navigator as the 175) via arinc429 and to my aera 760 via rs232 and the system works as expected, lateral nav from the 760 and lateral and vertical nav with coupled approached from the 375.

According to the gemini installation manual if the unit is receiving a 429 signal that will take priority over the rs232 input which seem to be the way it is working.

If I select a "direct to" on the 760 (internal) the AP will fly the GPS NAV track, if I then do a "direct to" on the 375 navigator the AP will switch to GPSS mode and fly that track and any resultant selected approach.

My 760 outputs the rs232 at 9600 baud and uses the NMEA & VHF Out setting (send frequency data to the SL30)

Hope this helps
Figs

 

[FlyPig]

Need NMEA

Thanks for the perspectives so far.

I have the RS232 out on the GPS175 configured to "Aviation" format but Mid Continent says it needs NMEA, which Garmin says isn't a format they use any more. The real problem may be Bendix and Mid-Cont not really trying to support the Trutrak and just guessing...?

It sounds like what the Garmin is putting out should work but I can't find information in how to configure the Gemini to read it. I've touched the screen to set up airspeeds, etc. but haven't come across anything explaining how to configure the input. I'd appreciate more on that.

 

[Longez]

To my surprise, the Gemini Installation Manual doesn't provide any guidance on setting baud rate.

Section 5.2.2 of the Gemini Operating Manual has the guidance I posted above on setting baud rate.

Steve

 

[TruTrakAndrew]

Aviation format works just fine and it is at 9600. So you need to set the Gemini to 9600…it was likely at 4800 for the 496.

If GPSS is working and serial is not, it *could* be that there is an issue with serial output on the 175. The 175 has been working with the Gemini in the past.

 

[FlyPig]

BAUD!

All,

As this story ends by setting the correct baud, I would like to thank you all for getting me on Trak (ha!) and add that though the Gemini gives ARINC priority for navigation it still NEEDS RS232 serial for position or it will not have context from which to reference the GPS steer. In other words it will stay in gyro mode and only allow you to horizontally command bank angle. So it's not either/or but rather both/and.

Tailwinds,
Chris

 

[uk_figs]

All,

As this story ends by setting the correct baud, I would like to thank you all for getting me on Trak (ha!) and add that though the Gemini gives ARINC priority for navigation it still NEEDS RS232 serial for position or it will not have context from which to reference the GPS steer. In other words it will stay in gyro mode and only allow you to horizontally command bank angle. So it's not either/or but rather both/and.

Tailwinds,
Chris

Not sure I understand this comment, on my setup the 375 only talks to the Gemini via arinc 429 and seems to work fine, flies 'direct to' lateral nav and fully coupled approaches. In a number of other installation wiring diagrams I looked at before wiring mine the 175 and 375 connection to the Gemini only connects the 429 output to the Gemini and I dont understand why you would need both a 429 and rs232 connection from the navigator. Maybe I misunderstand the comment.
Figs

 

[FlyPig]

Not sure I understand this comment, on my setup the 375 only talks to the Gemini via arinc 429 and seems to work fine, flies 'direct to' lateral nav and fully coupled approaches. In a number of other installation wiring diagrams I looked at before wiring mine the 175 and 375 connection to the Gemini only connects the 429 output to the Gemini and I dont understand why you would need both a 429 and rs232 connection from the navigator. Maybe I misunderstand the comment.
Figs

Or maybe I made a false assumption. The incorrect baud probably made the RS232 unrecognizable but allowed the ARINC only through the first door.

Thank again, folks!

 

[uk_figs]

Or maybe I made a false assumption. The incorrect baud probably made the RS232 unrecognizable but allowed the ARINC only through the first door.

Thank again, folks!

Apparently not, according to Andrew the Gemini needs the RS232 as the primary input and the 429 is secondary. It doesnt care where the 232 comes from so in my case it is coming from the Aera 760 so everything works fine. Guess I will add a RS232 from the 375 to the Gemini along with the 429 like you did and just use the 375 for AP control.
Learn something new every day.
Figs