Serial Wires and Other Stuff

[PaulR]

I'm working on a wiring "book" for my plane so that it's a little easier to wire and work on down the road. With that in mind, I'm doing single page drawings in cad of each "system". I recieved my SL-30 this week and I think I have the Comm side of it correct to the PM3000 but when working on the nav side I have some questions.
Equipment in panel includes SL30, D100, D120, PM3000, GTX327, 496.

I believe that the "Serial Tx" wire from the 496 goes to the "Serial Rx" pin on the D120 and if I want to "push" freqs. to the SL-30 it also goes to the "Serial Rx" on it. Correct? The serial lines can be hooked up to more than one thing for different purposes?

Second question is the Garmin and Dynon wiring plans don't show these RS-232 wires to be shielded. Is that correct or am I missing something.

I am really enjoying the wiring. I comfortable with the power, switching and grounding, it's this serial and audio that I'm really studying on.

Anyway, thanks for the help.

[vlittle]

Hi Paul.
My recommendation is to use shielded wire for the serial lines.

Normally, RS-232 signals are noise immune, although they may radiate some noise. In the case of the 496, however, it does not drive the proper RS-232C voltage levels, so it's signal is less immune to interference.

Therefore, the shielding helps. It's ok to hook up 4 loads to the Garmin (I've done it), but if you have problems it may be necessary to install a level converter. If you think you need one, let me know via PM. At one time I used to sell them and I may have a few circuit boards in stock.

Vern