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SL30 Comm Failure - with Dynon Skyview only

Junglepilot

Junglepilot

Well Known Member
Just got everything wired and did a smoke test tonight.

First Garmin SL30. TX & RX fine over headets front & back with wife using a King handset.

Then turned on Dynon Skyview. Powered up fine. Configured fine. GPS worked. etc etc.

Then I looked over at the SL30 and I saw a message "COMM FAILURE". Hmm.

I turned off the Dynon, and almost instantly the Comm Failure message left and frequencies were displaying as before & back up. Turned Dynon back on and a few minutes later SL30 again says COMM FAILURE. HMM.

Thought it might be a power issue. Charged battery to 12.5v. However same results exactly with full battery.

Someone suggested on an older thread that maybe this is an issue with the SR232 serial connection. This makes some sense as that is the only connection between the two units. But that's a pretty basic connection. Double checked the schematic from my avionics guy. RX to RX, TX to TX, and AF ground connected. Unless I'm missing something.

Any ideas? Things to check? I'm almost certain it will be a simple solution. Believe the Garmin is fine. I think the Dynon connection is the issue.
 
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Jungle Pilot said:
Someone suggested on an older thread that maybe this is an issue with the SR232 serial connection. This makes some sense as that is the only connection between the two units. But that's a pretty basic connection. Double checked the schematic from my avionics guy. RX to RX, TX to TX, and AF ground connected. Unless I'm missing something.
Click to expand...
Unless I've read things wrong, you should have the SkyView TX wired to the SL30's RX and the SL30's TX wired to the SkyView's RX pins.

One transmits to the others recieve port. The way you have them wired, they're both transmitting serial data to the other's transmit port. ;)
 
That was one thought I had

Yes that was one thought I had. The SL30 sends data on TX and the Skyview receives on the RX wire and vice versa. Like "you talk (Transmit) and I listen (Receive)".

So you're saying for example the RS232 serial wire from SL30 marked "Transmit/TX" should be attached to the appropriate Skyview serial wire labeled "Receive/RX"?

Thanks.
 
TX -> RX

So I think your COMM Failure is your RS-232 wiring. In general for RS-232 the labeling of signals is always relative to the device the creates or uses them. TX would be an output and RX would be the input. That means you need to connect the TX(output) of one box to the RX(input) of the other, and vise versa.

I'm pretty sure this is your problem.
 
Thanks

Thanks everyone. That was it. Switched the serial TX & RX wires with their opposite from the SL30 serial wires from harness and COMM FAILURE message seems to have disappeared.

Dynon should cover this in manual IMHO.

For anyone else:

SL30 Serial TX -> Connect to Dynon Serial RX
SL30 Serial RX -> Connect to Dynon Serial TX

Thanks!
 
I love this forum!

Iwas having these symptoms together with th NAV data not getting to the PFD. After trying various set-up changes to no avail, I searched the forum and - voila!

A quick check of the connections revealed the rx/tx cross-wired (or NOT cross-wired as the case may be........)

Doh!!
 
SL-30 TO SKYVIEW

Sandy

''Dynon should cover this in manual IMHO.''

It is cover in the manual Sandy......
-------------------------------------------
 
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Not always intuitive ...

Until I talked to Carlos at GRT, I too did not realize that you wire the TX port on one device to the RX port on another. Otherwise, Seems awfully logical to match TX to TX and vice versa.
 
It's in the Dynon Manual (page 4-15 of the SkyView manual), and it's also in many other brand manuals as well (including the GRT and GARMIN interconnect diagrams). If you have an "avionics guy" telling you to hook the TX/TX and RX/RX then you should probably find a new avionics guy because that's one of the more basic tenements of both older and newer avionics.

I can see how it might be confusing to a neophyte, but shouldn't be for an experienced person.

Cheers,
Stein
 
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Not logical to match tx to tx or rx to rx if you know:

Tx = Transmit
Rx = Receive

Then it's logical to connect the transmit port of one device to the receive port of another

Then again, I spent many an hour in the early days of hombrew computers debugging serial ports.
 
I have to admit that I'd assume the TX port on one would logically have to be connect to the RX port on the other. I mean, that's the way information flows - transmitted from one and received on the other.
 
SkyView Serial Ground??

Help!
I am connecting SL30 serial to SkyView harness. I understand Rx/Tx now, very helpful, thanks!
New question: The SL30 has a pin for "serial ground" for the shield braid. The SkyView manual makes no mention of a serial ground. What should the serial ground be connected to at the SkyView harness? I am out of ground connections at the SV 37 pin harness connections.
Thanks for any help, it would be nice to get this right the first time... Maybe this is common knowledge, couldn't find it on search.
- Roger
 
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