TCP data from AIS/GPS drops out periodically

[Ryban]

I've notice this problem in OpenCPN where every 30s or so, the GPS position is temporarily lost for a few seconds, and then returns. It's only mildly annoying, but I feel like it shouldn't be occurring at all.

See this video for an example, which also is showing the NMEA debug window:
https://youtu.be/Yt1keDM_ub4

• AIS unit is an ACR AISLink CB2 sending AIS targets and GPS data over TCP.
• AIS unit is connected via WiFi to a router.
• Router is connected with an ethernet cable directly to the mini PC running OpenCPN.
• All other connections in OpenCPN are disabled during this testing

It looks to me like the AIS unit is sending data every 1s -- maybe that's too frequent for some reason?

[nohal]

It looks to me like there is no data received at all for 10s between :46 and :56, in which case the position is obviously timing out and reappears as soon as new data is received at :56.
The reason for that may be pretty much anything (But I somewhat doubt OpenCPN based on what I see in the video). To completely discard fault on OpenCPN side, you may download PuTTY from https://www.chiark.greenend.org.uk/~...ty/latest.html and set it up like on the attached screenshot. You should see a constant flow of NMEA0183 messages in the window that appears, if it ever stops for a few seconds, something else in your system is at fault.

[Ryban]

That's a good idea, I'll do that when I'm over at the boat tomorrow.

[fxykty]

Send data using UDP instead of TCP?

[Ryban]

I'll try that too. When I was on the boat today I connected to putty and the data came in continuously without periodic interruption -- but I only watched it for a few minutes. It was dropping out every 20-30s while we were sailing today in OpenCPN, so the issue definitely persists.

I'll try UDP too. One thing that might also be relevant is that when I can't seem to get both my magnetic compass data (coming in on NMEA0183 through a USB dongle) and the TCP data from the AIS/GPS at the same time. Enable the TCP connection seems to prevent the NMEA0183 data on the COM3 port from coming in after about 20 seconds. I also noticed that enabling/disabling connections and checking "show NMEA debug window on/off will sometimes fix this particular issue, at least temporarily. However, this issue with the GPS is independent of the COM port data, as it has always been present before I was even attempting to bring that data in.

The other thing I could try is sending the data to my SignalK server that is running on the same device, and instead having SignalK send the data over to OpenCPN.

[rgleason]

Ryan, just a reminder, it never hurts to filter Out stuff you do not need or want, from within Opencpn, under Connections.

Originally Posted by Ryban

I'll try that too. When I was on the boat today I connected to putty and the data came in continuously without periodic interruption -- but I only watched it for a few minutes. It was dropping out every 20-30s while we were sailing today in OpenCPN, so the issue definitely persists.

I'll try UDP too. One thing that might also be relevant is that when I can't seem to get both my magnetic compass data (coming in on NMEA0183 through a USB dongle) and the TCP data from the AIS/GPS at the same time. Enable the TCP connection seems to prevent the NMEA0183 data on the COM3 port from coming in after about 20 seconds. I also noticed that enabling/disabling connections and checking "show NMEA debug window on/off will sometimes fix this particular issue, at least temporarily. However, this issue with the GPS is independent of the COM port data, as it has always been present before I was even attempting to bring that data in.

The other thing I could try is sending the data to my SignalK server that is running on the same device, and instead having SignalK send the data over to OpenCPN.