Trig TT-22 with GRT HX

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jnewsum1
Posts: 31
Joined: Sun Mar 02, 2014 2:49 am

Trig TT-22 with GRT HX

Post by jnewsum1 »

If I have a GRT Safefly 2020 GPS module connected to my Hx EFIS for GPS navigation data, will the HX transmit ADS-B GPS data to a Trig TT-22 xpndr via the RS-232 serial link from the HX to the TT-22 that transmits control and alt encoder data to the TT-22?

Or do I need to make a direct connection from the Safefly 2020 GPS to the Trig TT-22 for ADS-B compliant GPS position data?

Figure 2-5: GRT Trig Adapter Wiring Diagram, in the GRT Trig TT-22 installation supplement specifies in Note 2: "that a GPS connection to the TRIG serial adapter is not needed" but what isn't clear to me is if this applies when the TT-22 is being used provide ADS-B Out.
Bobturner
Posts: 437
Joined: Mon Mar 11, 2013 6:34 pm

Re: Trig TT-22 with GRT HX

Post by Bobturner »

If you read all of note 2 it goes on to say ‘connect a 2020 compliant gps here’. Confusing, but yes, your answer is that for adsb out you need a direct connection (rs232) from your gps to pin 5 on the adaptor. Don’t forget a ground connection, too. The reason for this is that the adsb position specifications are so tight that even a small internal delay going from gps to EFIS to transponder cannot be tolerated, plus there’s a lot more data than just position being sent out. While you are at it, make sure pin 13 (‘power on’) of the adaptor is grounded. I think this is supposed to be done internal to the adaptor but it doesn’t hurt to double check. If it’s not grounded internally just run a jumper to a ground pin.
I have this system (except I use a 420W for the gps) and it has worked flawlessly, along with a Skyradar D2 for adsb-in, connected via USB to the Hx and via wireless network to an iPad running WingX.
jnewsum1
Posts: 31
Joined: Sun Mar 02, 2014 2:49 am

Re: Trig TT-22 with GRT HX

Post by jnewsum1 »

Thanks Bob, you confirmed my suspicions on needing the direct connection from the GPS to the Trig on pin 5. I reread the SafeFly GPS install manual again and this connection is defined in Trig TT21/TT22 wiring and configuration section. The wording of Note 2: was confusing to me. Needing a ground on pin 13 (power on) of the Trig is also good info. I will make sure to confirm whether the adapter does it internally or not.
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