I need to output GPS-250 data to GTX-327 transponder to enable the feature that automatically switches the transponder from Stby to Alt. Can I pickup the GPS transmit data from an open serial TX port on Skyview ver 2.6 or do I have to have to actually splice into the TX line from the GPS-250?
GPS data out to GTX-327
- Thread starter dbdurrett
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rfazio1951
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I have a Garmin GTX-327 and it switches from standby to alt automatically when it senses the plane is off the ground. You can set it to do that in the configuration pages of the unit. You can download the installation and configuration manual from garmin.
mmarien
Murray M.
The GTX327 will switch modes if it receives ground speed from a GPS device or the squat switch state changes. The Skyview doesn't output any GPS information according to the current manual. The GPS-250 is a position device only so I suspect it's only outputing NMEA position data and not speed or routing. If it does, it too fast (38400 baud) for the GTX327 (9600 baud).
You might get the GTX327 to switch if you connect another GPS device that outputs NMEA data to a serial port. The GTX327 has two serial ports. The second (pin 2) is RX only. If you connect the first port (TX and RX) to the Skyview it will sent altitude data to the GTX327 (Mode C) and display data from the GTX327 on the top line of the SV display. You have to specify ICARUS data in both the Skyview and the GTX327. The GTX327 may switch modes if it receives GPS ground speed from a NMEA sentence from a GPS device on port 2.
I say might as I haven't tried it. I'm going to connect my GPS495 serial out to the GTX327 serial RX on port 2 but I won't be flying until next spring so can't test it until then. How is your's connected Richard? and what does it use to sense that it's airborne? GPS ground speed or the squat switch?
You might get the GTX327 to switch if you connect another GPS device that outputs NMEA data to a serial port. The GTX327 has two serial ports. The second (pin 2) is RX only. If you connect the first port (TX and RX) to the Skyview it will sent altitude data to the GTX327 (Mode C) and display data from the GTX327 on the top line of the SV display. You have to specify ICARUS data in both the Skyview and the GTX327. The GTX327 may switch modes if it receives GPS ground speed from a NMEA sentence from a GPS device on port 2.
I say might as I haven't tried it. I'm going to connect my GPS495 serial out to the GTX327 serial RX on port 2 but I won't be flying until next spring so can't test it until then. How is your's connected Richard? and what does it use to sense that it's airborne? GPS ground speed or the squat switch?
rfazio1951
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I went back and read my manual. It senses liftoff by the squat switch. I don't know that it can use GPS data to sense lift off? It accepts GPS data to include in it's output?
There are differences in how this works depending on the firmware you have.
Some have reported that it will turn on via GPS but not off or vice versa (can't remember which) and others have claimed it works fine.
At least a couple I have heard of have given up getting that to work and just went with an air switch connected to the pitot line and connect that switch to the squat switch input on the xponder.
There was some talk here in the past on what switch to use.
There was also a bunch of talk about what format the transponder was expecting to see. I think it ended up with the xponder requires AVIATION format not NMEA to get this to work.
Some have reported that it will turn on via GPS but not off or vice versa (can't remember which) and others have claimed it works fine.
At least a couple I have heard of have given up getting that to work and just went with an air switch connected to the pitot line and connect that switch to the squat switch input on the xponder.
There was some talk here in the past on what switch to use.
There was also a bunch of talk about what format the transponder was expecting to see. I think it ended up with the xponder requires AVIATION format not NMEA to get this to work.
mmarien
Murray M.
This should work according to this post on VANS forum 
http://www.vansairforce.com/community/showthread.php?t=15795
Does anybody have the latest software update for the GTX327. Mine is 2.02 and it doesn't airborne sense or interface with SV - other than receiving pressure altitude.
http://www.vansairforce.com/community/showthread.php?t=15795
Does anybody have the latest software update for the GTX327. Mine is 2.02 and it doesn't airborne sense or interface with SV - other than receiving pressure altitude.
mmarien
Murray M.
I had the firmware on my GTX327 updated to the latest version while I was doing my annual. The GTX327 Port 1 RX/TX is connected to SV Port 1 RX/TX. I connected the second GTX327 serial RX line to my GPS495 TX. Two things happened. It now displays status on the Skyview top line and I noticed that it switches to ALT when it detects that I'm airborne. Haven't seen it switch to STBY when I land yet.
The GPS495 TX feeds NMEA data to SV and the GTX327 and VHF data to my iCOM210 so it's a three way split on the TX line.
Haven't seen it switch to STBY when I land yet.The GPS495 TX feeds NMEA data to SV and the GTX327 and VHF data to my iCOM210 so it's a three way split on the TX line.
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Just a note (and I think you understand this) that we only display status from external transponders. We don't issue any commands to them at all.
mmarien
Murray M.
True. The GTX327 is using the NMEA data from the GPS495 on the second RX port to determine airspeed and switches to ALT when it thinks it's airborne. I think if I wait long enough the GTX327 will switch to STBY on the ground. The manual says there is a programmable delay.
SV TX -> GTX327 RX(1) Icarus pressure altitude
SV RX <- GTX327 TX(1) Status
+-> GTX327 RX(2) NMEA airspeed (squat function)
|
GPSMAP 495 TX --+-> SV RX NMEA NAV data
|
+-> iCOM210 VHF frequencies
The GTX327 could probably use SV NMEA data output also. The $GPVTG sentence has speed. I still have two open SV TX ports.
SV TX -> GTX327 RX(1) Icarus pressure altitude
SV RX <- GTX327 TX(1) Status
+-> GTX327 RX(2) NMEA airspeed (squat function)
|
GPSMAP 495 TX --+-> SV RX NMEA NAV data
|
+-> iCOM210 VHF frequencies
The GTX327 could probably use SV NMEA data output also. The $GPVTG sentence has speed. I still have two open SV TX ports.