CAN troubles with Black Jaguars

[Levansic]

I have a little follow-up on our original discovery and fixes. Tonight, I was setting up a new 2CAN, and only had one of our 2012 KOP black jaguars connected, when I noticed that my status readings dropped to all zeros.

Up until this point, this unit was always the first in the chain, and acted as the serial to CAN bridge. After fixing the RJ-11 port, I hadn't had any connectivity issues. I had to repair both of the ports in the second 2012 KOP black jaguar, but I thought this one was OK.

I wiggled the cable (4-conductor CAN-only) in the RJ-12 port, and I got intermittent status on the web dash board. So I popped the cable out of the RJ-12 port, and I see that pin 3 and pin 5 wires are almost flat, as I described above. I disconnected the power, did my tweezer trick on both of the wires, and hooked everything back up.

The result was rock-solid communications over that port.

How did I miss this? Well, this was the unit I used to bridge all of the others with, when I fixed the others. Pin 1 and 6 were fine, giving a good serial connection. With small cable runs and only two nodes on the bus when I was testing, I didn't see any termination issues. I'm sure that if I used this unit to connect four or more jaguars using the serial bridge, we probably would have had maddening missing termination issues as this port jiggled. The constant connection to this bridging jaguar (over serial) would have masked this problem and pointed to the next in the chain or the last in the chain.

In summary, I now know that 100% of our CAN ports (RJ-11 & RJ-12) on our 2012 black jaguars had quality issues that prevented them from working reliably out of the box. You have to test all ports in pure CAN communication, so that you make sure that your bus actually is terminated on both ends. The fix is easy, if you are careful and patient. If you are afraid of breaking the ports, recruit a dentist as a mentor.