pic: cRIO CAN Jag

Picture taken in Austin, Texas Convention center in the exhibit area for the American Society of Engineering Education. NI had a booth similar to the one in Atlanta but their demobot no is using CAN addressing with the cRIO via the module pictured. The booth attendant could not / would not comment on the possibility of this module being included in the FRC 2010 kit of parts. Speculate away if you like.

Very cool. I’m crossing my fingers that this is a “go” for 2010…

I like how they just left the head of the cable in the last jag (:

Thats really cool. daisy chained jag’s look intimidating without those silly 3-color wires coming out of them.

Does the idea of having (potentially) all of your speed controllers in series scare anybody else?

One would assume that the CAN pass through circuitry is sufficiently removed from the motor driver so that even a “blown” Jag wouldn’t bring down the entire network. Even if that is the case it seems like this configuration could lead to a really tough time debugging your electrical system.

Look at it closely. I’m pretty sure that’s a termination resistor, something typically used to suppress signal reflections at the end of a high-speed bus like CAN.

Eh, not really. CAN is reasonably fault tolerant. I’d be more afraid of a cable coming out or a device on the bus going “babbling idiot mode” than one Jaguar electrically disabling others.

Quoted for Truth. Standard CAN usually has 120 Ohm termination resistors on either end of the bus.

THe only thing that worries me is all those RJ45 connectors in series…you saw what happened to similar connectors on the DS this year when used in a competitive environment.

Well, ideally your electronics would be in a low impact area on your robot, right?


Yeah, right :slight_smile:

Finding a low impact area is difficult to do in the situation where a 150lb robot going 12fps slams into your bot.

If anything we can do the clear nail polish thing again. It worked wonders on the IFI PWMs and it still works great on my R/C car.

Unfortunately the RJ series connectors are inherently flaky…

Please don’t assume that because KwikByte chose to use an unacceptably inferior component that TI/Luminary did as well. RJ connectors come in many forms and many quality levels. If you squeeze cost out hard enough, any component can become a failure point.

In my opinion, I hope they release the module before season so we have a few week to play with it. Even though none of our pwm’s ever came out, I personally would feel better if we used CAN.


What I like about CAN is removal of several PWM wires all traveling the same path and having to check which pin number it was in and verifying correct orientation on both ends several times during the build when things would get disassembled and reassembled. With CAN, 1 RJ45 cable from the cRIO from just the CAN bumper to the first device and then daisy chain from there. No need to verify orientation and keep the log of which pin to which device … all that is in the code and addressing log.

How many times did your robot temporarily lose functionality after a re-build because a PWM was not inserted into the correct pin …:ahh:

Unfortunately, cost seems to be the primary design consideration for the RJ series since it’s inception decades ago.

Hopefully Luminary has figured out how to make the system reliable…but my long experience with the connector series isn’t good.

Please cite your source …

… and compare the 'flaky’ness to the 3 pin non locking PWM cables we’ve used in the past.

My source is 35 years of playing with electronic stuff.

The PWM cables are not wired in series…the CAN bus is a daisy chain. Any one poor connection can kill the rest of the chain.

The saying ‘You Get What You Pay For’ comes into play with RJ connectors. If you want reliability you’re going to pay for it.

I hope some time and money is being invested in to the short commings of the jag. Next year we may be back on carpet and It’s my opinion that the are several points of failure that could cause some serious problems when first teams start to abuse them. I would rather have a solid Hobby PWM jag that is robust than a weak can jag.

From my rudimentary knowledge of CAN bus topology, I believe the Jags can be arranged in a ring, thus providing some connection redundancy. The Luminary folks at Championship thought this could be done as well. Does this make anyone sleep better?