GPS-175 & GNC-215 preferred connection to Skyview HDX (w/ ARINC429)

[cbretana]

The GPS-175 obviously has to use the ARINC-429 to connect to the HDX, and the GNC-215 does conform to the SL-30 protocol, so it likely can use one of the HDX serial ports to connect to the HDX. The ARINC-429, however, has two inputs, (A & B), and the GNC-215 also has a ARINC-429 output so it should be able to connect to the Skyview HDX through the ARINC as well. Are both of these choices equivilent?

I just read that most recent release of the Skyview software implements the capability to inject (send) COM & NAV frequencies from Skyview, (on the HDX), to the GNC-215 standby frequencies. Is this capability implemented across both the SL-30 and the ARINC-429 connection approaches ??

 

[cbretana]

Had an informative conversation with Dynon support engineer Jessica on this issue.
Bottom line, except for certain specific scenarios, use serial (RS-232) port for the GNC 215.
1. The GNC-215 features that require using the ARINC-429 also require that it is the only COM transceiver in the plane, or is set up as the primary one, and the Dynon VHF COM transceiver has much better features that also require it be the primary transceiver.
2. Obviously, if you have already used all 5 serial ports on the HDX, you need to use thw AIRINC-429 interface.
3. Another scenario where you might need to use the AIRINC is if you don't have the latest (ver 17.3) release of the Skyview software. This has to do with a bug in older releases, (fixed in 17.3), that only manifests when connected over the serial interface.

 

[cbretana]

Well, I received more info on this (related to the last option mentioned above), from Jessica (Dynon Technical Support Engineer).

The background here is that Garmin used to have a CDI INDICATOR TYPE selection on the legacy GNC 255A/B units. This format was crucial for the previous Dynon Serial interface because we required the GNC 255 to be configured for CDI INDICATOR TYPE: NONE. This config allowed the CRS needle to be utilized from the GNC 255 without issue.

When Garmin released the GNC 215, they removed that config menu and the device defaults to a serial indicator type. Using the existing Dynon GNC 255 config with the GNC 215 resulted in the course needle not being present, unless you first updated the CRS through the GNC 215 CDI menu OBS adjustment. This would get the needle to show up on the SkyView display, and it would continue to work as long as you only updated the CRS/OBS on the GNC 215 and NOT the SkyView display. As soon as you would update the CRS on the SkyView, within 3 seconds the connection would break and GNC 215 would report OBS course lost.

The solution for this was for Dynon to change our software to support the serial interface with the GNC 215. This is what we did. But we did not roll back and replace the existing GNC 255 configuration.

Software versions prior to 17.3 require the combination of the RS-232 serial interface + the ARINC 429 navigation interface. What we have not tested is ARINC only. That may not provide all of the information like the tuned nav frequency in the HSI SOURCE box. Some of that data comes through RS-232.

The difference is in the configuration. Normally the GNC 255 would be configured for SERIAL IN DEVICE: GNC 255 A/B, and the SERIAL IN FUNCTION set to NAV 1. When you use the SERIAL + ARINC interface with the GNC 215, you still configure the GNC 215 on the serial port as a GARMIN GNC 255 A/B under SERIAL IN DEVICE. But you set SERIAL IN FUNCTION to NONE. You do this because the NAV 1 function comes through the ARINC instead.

On 17.3 and above, the serial communication change has been made and the Garmin GNC 215 is officially selectable from the serial in device list. When the serial in function is set to NAV 1(2,3,4) (On 17.3+) the serial-only interface will work correctly.

Everything below 17.3 requires the ARINC to avoid running into the communication error with serial only.