The Garmin 327 transponder control output doesn't transmit the altitude encoder labels. Altitude Encoder data has to be provided to the FreeFlgiht XVR on a separate serial port input. The Dynon 180 output supplying altitude encoding data to the transponder should be used to provide altitude encoding data to the FreeFlight XVR.
To clarify what Isaac wrote, the Freeflight TC978 control head has a built-in digital encoder with a static pressure connector on the back of the controller. If you, like me, are not using a modern EFIS with serial altitude output this built-in encoder is an added benefit when installing the Freeflight control head since it can serve as a primary or secondary digital altitude source, with automatic failover switching of encoder signal in the case of a second encoder onboard. The TC978's altitude encoding signal not only provides altitude to it's own Freeflight LRU but also to the GTX 327 and any other onboard digital device that can use a RS-232 altitude source. I didn't realize this until I received my unit and inspected the TC978 controller finding the brass barbed static pressure fitting on the back. It's like a freebie. That's when I changed my plans of having the GTX 327 stand-alone, and instead made room for the TC978 controller on the panel so I could remove my Trans-Cal RS 232 blind encoder and use it somewhere else.
When I called Freeflight technical support they encouraged the installation of the TC978 as a matter of course. They also told me if I didn't install the TC978 (despite having a GTX 327) then I would have to install ADS-B out status annunciator lights somewhere on the panel (yuk). Combine this with having to install a maintenance serial port, personality module and and using an older laptop with a serial port running terminal software to configure the ADS-B parameters, it really does make everybody's life easier to go ahead and install the TC978.
On a related note, I opted to substitute an AT575-9 GPS antenna from an old Apollo GPS360 in place of the big 'ol honkin' RAMI AV-801 antenna that Freeflight includes with their units.
(Used AT atnenna. O-ring gasket temporarily removed during old silicon sealant clean-up)
That substitution of WAAS antennas is allowed per the installation instructions as they list the old Apollo GPS antenna part number as an approved alternate. The AT575-9 is lower profile, less drag and has a smaller footprint for tight spaces. Here is a photo I took of both antennas side by side, with the included Freeflight RAMI AV -801 GPS antenna on the left and the re-purposed Apollo AT575-9 GPS antenna mounted and sealed on an Aviat Husky wing root fairing on the right. The Husky, with it's interfacing structure, just didn't have enough real estate for the Freeflight RAMI antenna:
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One final note. My install is for the "out "only version TXL. I am a real believer in being able to choose or change my "in" source by using any of a myriad of portable "in" choices out there. All the while with options like built-in attitude AHRS and/or backup battery power (like GDL-39 3D etc...). Portable "ins" are also "dual band" pickup up both frequencies despite my out being UAT only. This separate in/out scheme allows the flexibility of being more future proof. And it's cheaper to only buy only one portable ADS-B receiver, especially if you own and fly multiple aircraft and take the "in" with you and pop it in place before engine start.
The FreeFlight UAT ADS-B unit with built-in WAAS GPS, when combined with an existing or used GTX 327 and a portable dual-band receiver is about as cheap a set up as is currently possible. Used GTX 327's are a bargain on the used market right now.
I couldn't find a better price on the TXL out unit than Walt's price above. It is exactly what I paid for the same unit.
Jim
