SCX20 drops off network after a number of hours (no address claims anymore)

[merrimac]

Hi all,

I've got an SCX20 that has developed an issue that I did not notice before. The SCX20 has been installed since 2021. No issues before 2025. Full B&G system with a Garmin Cortex thrown in as well as CANboat + Signal K.

The symptom is that after about a day or two the device no longer periodically generates its address claim or product information. It does still produce heading and position data etc.

To try to fix this I let CANboat generate a PGN 59904 request for all devices to produce their address claim (PGN 60928) and product info (PGN 126996). The SCX dutifully obliges and does this like all other devices. However, after a (very long while) it sometimes stops doing this. I see no rhyme or reason to why, other than a possible memory leak in the SCX20. I can reset its part of the bus, but then all devices lose heading for a while which is not great.

Any ideas? I'm on firmware 2051601-01.04 (as reported by PGN 126996)

Is there a way to update the firmware other than with a Furuno MFD? I hate spending 2 or 3 boat units just to do this and then find out it doesn't help...

 

[Quitsa]

Are you sure that all of your wiring is still in good shape especially the power tap for the NMEA 2000 backbone? My experience is that the SCX-20 is pretty sensitive to transient voltage drops. Sometimes my SCX-20 would drop off the network when I start my Diesel engines and not reconnect because the battery combiner will close briefly and the house batteries will share the starter loads. I have to shut the power to the electronics and restart and then the SCX-20 reappears. Now I make sure to start one of the engines first even though the issue does not always appear.

 

[merrimac]

Yes, the NMEA bus is fed from a separate big Lithium battery just for the nav stuff, the rest of the boat is 24V.

If power was the issue it would occur at a more random interval, but it never happens on the first day of sailing.

 

[Quitsa]

This question may reflect my ignorance. If the SCX-20 is producing all of its data PGNs for heading, position, attitude, and so on, when you note the issue, why does it matter if it is not transmitting the product related PGNs?

A power issue could be caused by another device on the NMEA 2000 network, which would not necessarily be random although it is hard to see why it would occur only after a couple of days. Is the drop cable to the SCX-20 very long? I am sure that is one reason mine is sensitive to voltage. It is mounted up on the sunshade for my tower and has a longer than recommended drop.

 

[merrimac]

It is not claiming an address anymore and it also stops sending its product information. Other devices use this, rightly so, to understand what they are listening to. It has nothing to do with product specific PGNs.

 

[merrimac]

Also, although some devices were swapped out, this is on the other side of the bus and this side has its own power tap using an Actisense QNB-1. It only contains 3 primary devices: the NMEA gateway, the SCX20 and a B&G WS320 wind wand (using a short cable, it connects to the wind sensor wirelessly.) but I suppose I could try disconnecting the SCX and move it closer or measure the voltage at the device itself. In the end maybe build a separate network for testing and run on the backup GPS and compass for a while...

The thing is this has been happening both with a fully loaded network (~ 20 devices) and with just 3, at night at anchor as well as during the day both moving or lying still. Temperature has been all over the place as well.