Skyview NMEA output

[paulrkuntz]

I have an ACK E-04 ELT in my airplane, which will accept RS 232 NMEA navigation input. The new Skyview 3.2 firmware provides RS 232 NMEA data on a serial port, so I decided to hook it up. So today I configured previously unused serial port 2 for NMEA Basic output, 9600 baud. I left serial port 2 input at None. The GPS was at that point working fine. I have two displays, so I configured both displays the same way.

Then I wired the two display serial 2 lines in parallel and connected them to the ELT RS 232 lines. I wired the Dynon serial output to the ELT serial input and vice versa. The only other connections are +12 volt and ground connections in the shielded wire going to the 4-pin ELT connector.

After completing the wiring, I powered up the system and now I'm getting Position Fail with the big red X on the Skyview displays. Checking GPS fix status on the configuration screen I see:
GPS Source: POS 1 - Active
Fix Quality: No data

My plane is in my hangar, but the GPS has been working consistently before now. Are these symptoms consistent with weak satellite signals? The weather did deteriorate while I was working on the installation today, so maybe it's just coincidence that this happened after hooking up the NMEA ELT output, but I'm suspecting that something changed that has caused the GPS to stop working.

Any suggestions?

 

[paulrkuntz]

Further information on my previous post:

I hadn't looked at this detail before, but currently I'm seeing:

Skyview display one --
Serial Port 1 (Dynon 262 transponder):
transmit counter increasing rapidly
navigation data increasing about approximately 0.5 Hz
Serial Port 2 (NMEA to ACK ELT):
Serial in device: none
baud rate: 9600
Serial out device: NMEA Out (Basic)
data counters: all fixed at zero
Serial Port 5 (Dynon SV-250-GPS):
Serial in function: POS 1
Serial out device: none
Navigation data increasing at approximately 0.5 Hz
All other data counters fixed at zero

Skyview display two:
Serial Port 1 (Dynon 262 transponder):
transmit counter increasing rapidly
navigation data increasing about approximately 0.5 Hz
Serial Port 2 (NMEA to ACK ELT):
Serial in device: none
baud rate: 9600
Serial out device: NMEA Out (Basic)
transmit counter: increasing by an increment of 124 every second
all other counters fixed at zero
Serial Port 5 (Dynon SV-250-GPS):
Serial in function: POS 1
Serial out device: none
Navigation data increasing at approximately 0.5 Hz
All other data counters fixed at zero

It's interesting that the serial output to the transponder looks the same on both displays, while the serial port 2 transmit data counter is incrementing on only one display. The serial port 5 transmit and receive counters are fixed at zero on both displays, and both displays are increasing the nav data counter at 0.5 Hz.

 

[dynonsupport]

There's no relationship that should have caused the SV-GPS-250 data to stop being received when you hooked up serial port 2.

Behind the scenes, when there are multiple SkyView displays (and serial wiring is as specified - paralleled to all displays), the displays will "take turns" transmitting to serial devices. You have no direct control over with display is the one doing the transmitting.

So, to try to isolate the trouble a bit:

1. Try powering down one SkyView display - push and hold Button 1.

Does the transponder start working, does the map start working?

2. Try powering down the other SkyView display and powering up the one that was off.

Does the transponder start working, does the map start working?

 

[dynonsupport]

And FYI, a big red X means that no GPS data is being received at all, while a flashing "?" means that we have data, but it indicates no lock.

So in your case, there is no data getting to us from the GPS at all, not just an issue of you being in the hangar with no satellite lock.

Also worth trying is setting your configuration back to the settings from before with no NMEA out configured to see if it works. This will tell you if it's a software thing or a hardware issue.

 

[paulrkuntz]

I've already tried both suggestions.  That is, I tried it with each display being the only one powered up, and I tried returning the serial port configuration to its former state.  You answered my primary question, which was what the red X and Position Fail means.  

I am now thinking that somehow in the course of routing wires to the ELT to connect the NMEA data, which involved removing wire ties under the cockpit floor (by feel), I clipped a wire or perhaps pulled a wire out of a butt splice in the GPS cable.  Would this cause the observed symptoms?  If so, can you identify the most likely wire break out of the four wires in that bundle?

 

[dynonsupport]

Cutting the black, orange, or grey-violet wire on the GPS puck would all cause this exact issue, so there isn't a way to narrow it down more. It's not the grey-orange wire if that helps at all

 

[paulrkuntz]

To put it another way, can I determine from the symptoms or from the Skyview configuration menus if I have a GPS wire break, and which wire is broken? Or do I have to bite the bullet, rig up a continuity tester and start probing my wire bundle?

 

[paulrkuntz]

Sorry, I missed your answer. Thanks, I'll dig into it when I get back to working on my plane later this week.

 

[jakej]

DS - I've seen the same symptoms on a dual SV-GPS setup by an other installer.  My fix was to install a connector about 1 ft from each Gps puck, do a continuity test to that point for SV & then swap antennas for  troubleshooting.  Turns out that there was some damage (no visual evidence) right at the puck.

HTH

Jake J

 

[paulrkuntz]

I'm finally getting around to reporting resolution of my problem. The key was a Dynon moderator reply back in October confirming that a cut wire could cause the symptoms that I was observing. I checked the wiring under my cockpit floor and sure enough, I found that I had clipped a GPS wire when cutting the ends off some wire ties. It was one of the three wires that were suggested as the likely culprits. After splicing the cut wire, the GPS immediately started working and I got a good test of the NMEA signal to the ELT. Thanks again for great support, Dynon!