Tuesday, December 6, 2016

Compatibility Issue Discovered Between Dynon SkyView And Garmin GTR 200 Radio

Have discovered a compatibility issue between the Dynon SkyView Touch and the Garmin GTR 200 radio installed in the DOG Aviation RV-12. Below is a detailed description of the issue and a workaround what works.  I felt Dynon support should be made aware of the issue and have notified them about the problem. If there is a solution forthcoming, I’ll return from the future with the info and edit this post accordingly. I’m guessing the solution will ultimately require a SkyView software update.

Before going into the “issue”, for the reader’s benefit, the aircraft/avionics configuration is a Van’s RV-12 outfitted with a Dynon SkyView Touch running version 14 software and a Garmin GTR 200 radio with the latest 2.7 firmware. The wiring and configurations are such that a list of airport frequencies can be displayed on the SkyView, the desired frequency can be pushed to the GTR 200 radio’s standby by pushing a button on the SkyView. Also, GTR 200 active and standby frequencies are displayed on the upper line of the SkyView’s display. The Garmin GTR 200 radio is wired to the SkyView’s serial port #4 and the device name of GTR 200 was selected for the serial port … all a standard Van’s RV-12 configuration. Additionally, I have wires running from switches on the control stick to the GarminGTR 200 radio’s discrete inputs 1 & 2 … one stick switch flip-flops the GTR 200's active and standby frequencies and the other stick switch cycles through the GTR 200’s COM user frequency data base.

A few weeks ago I decided to take advantage of the programmable COM user frequency database built into the GTR 200 and began entering all the pertinent frequencies for my home field and the CTAF (common traffic advisory frequency) frequencies for some the county airports within my assigned phase one flight testing area. I did not enter airport ID’s … instead, I used the actual name of the field such as Knox, Carroll, Wayne, Holmes, Clever, Downing, ect.

The "issue" I ran into is two pairs of airports shared the same CTAF frequency ... Wayne & Clever share one frequency, while Holmes and Downing share another. What’s the big deal you ask? Well, the name of the airport displayed on the GTR 200 radio was dependent on the order in which the airport name was entered into the COM user frequency database.

Example: Holmes was entered into the COM user frequency database before Downing and when cycling through the database and stopping on Downing, the GTR 200 would display Downing briefly then the name displayed would change to Holmes. This also happened when selecting Clever … Clever would display on the GTR 200 for a few moments and then the display name would revert to Wayne which shares the same frequency but was entered into the COM user frequency database ahead of Clever.
Here the COM user frequency database was cycled through to select Downing as can be seen in this photo … a few moments later, the name changes (see next photo).
As can be seen in this photo, without touching any buttons the name displayed in the previous photo on the GTR 200 radio has mysteriously changed from Downing to Holmes.

For the last week or so, I have been working with Garmin support via Email exchanges and looking at settings, etc. … all of which seemed to be correct. After verifying the settings were correct, one test Garmin support wanted me to perform was to power down the SkyView but leave the GTR 200 powered on and see if the names displayed correctly when cycling through the COM user frequency database … THEY DID!!! When I powered the SkyView back on, the names began changing again. This indicated the issue was actually being caused by the Dynon SkyView.

After another Email exchange, Garmin support suggested that I try changing the device name associated for serial port #4 from GTR 200 to SL40. I did that and it appears to have worked! The GTR 200 now displays the correct name for the selected COM user frequency in the database and the SkyView no longer mysteriously changes the selected name displayed on the GTR 200. Also, by changing the device name associated with serial port #4 to SL40, there has NOT been any loss of functionality … in that, the SkyView can still push frequencies to the GTR 200 radio’s standby and the active and standby frequencies selected on the GTR 200 display on the top line of the SkyView’s screen.

However, the same cannot be said for the airport name that the SkyView displays on the top line. For example: If the GTR 200 displays Clever 122.800  for the active frequency and Knox 123.050 for the standby, the top line on the SkyView  will display the correct frequencies for both the active and standby but does NOT display the name assigned to the frequency in the GTR 200’s COM user frequency database correctly. Instead, the SkyView changes the name to an airport code based on the frequency … resulting in a name code that may not correct as can be seen in the photo below.
One can see the Garmin GTR 200 radio’s active frequency is Clever 122.800 and the standby is Knox 123.050. However, when looking at the SkyView’s top line the Skyview displays an airport code of 3G3 for 122.800 and 15G 123.050 … the airport codes are incorrect for both those airports. However, 3G3 and 15G are valid airport codes for closer airports to the airplane's current position that share those same frequencies.

It appears to me as though the SkyView is looking at the current GPS position and selecting an airport name code based on the closest airport name corresponding to the selected frequency. I can live with the SkyView changing the name on its own display (rarely look at it anyway), but not on the GTR 200 radio … now that SL40 is selected, that is no longer an issue. As mentioned I don’t really look at the SkyViews top line showing the selected radio frequencies, so it is not a big deal that the airport name may not be correct from time to time. I would turn it off altogether … but should the display on the radio ever go on the fritz, the display on the SkyView can be used to see the frequencies the GTR 200 radio is being tuned to ... so the SkyView makes a great backup display for the GTR 200 radio.

Don’t know why the SkyView would mysteriously change the selected COM user database display name on the GTR 200 when the serial port is configured for GTR 200 … but it does for me. Sure glad changing the device name to SL40 solved the problem without a loss of functionality. I’m guessing this may not be unique to the RV-12 and will likely apply to any aircraft outfitted with a Garmin GTR 200 radio connected to a Dynon SkyView optioned to display com & display com in top bar.