[linuxboy]

[quote=RyanN;1168414
We have also been testing CAN out a bit, and found some unsettling results.

If you have an intermittent connection where a CAN devices does not appear on the CAN network, the whole CAN network will drop out, and the digital side car will not work. The thing is that the robot remains connected the entire time.
[/QUOTE]
I imagine the Digital Side Car not working is not a result of the CAN device dropping out, but rather, the error handling when a CAN device drops out is expensive and therefore watchdogs start tripping because loops aren't going fast enough and packets are processed quickly enough and suck.

[quote=RyanN;1168414
This was not the cause of our problem as we went back to PWM during Bayou, but I can see teams complaining about no communication due to this.
[/QUOTE]
Again, expensive error handling means the cRIO stops processing communication packets with the DS, and there for it "loses comms"
[quote=RyanN;1168414
We originally had 4 CAN-enabled Jaguars, IDs 2, 3, 4, and 5. ID 5 was the last in the chain, and had the terminator resistor installed. We wanted to test 8 Jaguars over the RS-232 to see how well it worked. Well, we assigned IDs 6, 7, 8, and 9 to the drive motors. When we plugged it all back in, nothing worked. We found out that when we extended the network, that the Jaguar with ID 5 had a bad RJ-45 port. To work temporarily, we rearranged the cables to make that Jaguar the last in line, and it all worked again.

So that's another idea that I had as far as troubleshooting.

We can't use the 8 jags though... I'm not sure if we reached the limit of RS-232 driving CAN, but we were getting tons of CAN timeouts, and Drive Motors not being called fast enough warning (in teleop). I analyzed the timing of Telop, and found that it ran every 10ms on average, but 60ms to 500ms spikes were not uncommon (where we saw the timeouts). When this occurred, we would also glitch/jerk.
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So, since the last Jag in line's other RJ-12 (RJ-45 is 8p8c I think, whereas the CAN plugs on the jaguars are 6P6C and 6P4C) port was bad, the terminator couldn't terminate, therefore it was like having no terminator. This wouldn't be an issue in a shorter chain since there isn't as much need for a terminator (I don't know why) but in a longer chain, it would cause timeout errors, and again, the error handling is expensive, so it would slow down the loop.