NAV/COM tuning with CNX80/GNS480

[N21HV]

I am getting close to the end of my electrical integration of my HDX system. I got my primary radio (CNX80) to talk to SV over ARINC interface where I can see the GS, LOC, etc show up correctly on the SV. I also have the serial connection connected between COM1 on CNX to COM1 on SV. I cannot, however see the COM frequency show up on the top bar, nor I can tune the radio through SV. Going into maintenance mode on CNX, I can see that some commands come through when I type in COM frequency on the top bar on SV so data appears to be going to CNX.
I suspect there is some settings I need to change on CNX to have it accept external commands.
Has anyone got this to work and is able to share your settings?

 

[ploucandco]

The GNS480 has internally an SL30 as NAV/COM.
The RS232 input/output of the SL30 is connected to a RS232 port of the microprocessor board of the GNS480. That commands the NAV/COM frequencies. So as this RS232 of the internal SL30 is already used, you cannot change frequencies externally.

What you can do is "monitor" the exchanges and so use the output of the internal SL30 (connector P7.5 of the GNS480 and P7.5 as GND) and tie it to the RxD+GND of a Skyview COM.

Normally, this way, you will get the Radio frequency information. You will not be able to tune-up the Radio on the GNS480.

 

[N21HV]

Interesting... The ground maintenance screen for CNX80 shows that COM1 RX can be set to SL30 mode. That seems to imply that it can receive SL30 commands. Installation manual 1.2.2.6 also states that the ports can be used to receive serial data. Furthermore, in section 2.8.10.1, the same manual talks about how the RS232 port can be used to transfer COM/NAV frequencies. (See attached image for reference.)

The test screen also shows that the commands are coming across so it implies that the pin 4 (COM1 Rx) is connected to some kind of intelligence inside the CNX80.
I posted on CNX80 users group to see if anyone has the remote tuning working to see if this above information can be verified (or refuted).
Hiroo

 

[ploucandco]

So these ports are for connecting an external SL30 that can receive NAV/COM data+DME distance from the GNS480.
Not what you want...
According to your first message, you want Skyview to read/tune the COM frequency. With the info that I gave you, you can read the COM frequency but not tune it.