CAN and Jaguars, any limits?

[krieck]

Reducing speed control messages where possible is a great idea, and I'm going to look into trying this.

In the case of our robot with 11 Jags on the bus however, we were seeing failures while the robot was initializing. In other words, some of the code was timing out when we first constructed the CANJaguar objects. The only traffic on the bus at this time should have been initial messages connecting to the Jags. No speed control yet.

Testing our terminating resistor is another avenue of attack, but in our case we saw the same problem on two entirely different configurations: our competition bot and also our experimental rig built from two other bots. I'm still at the same conclusion that ten CAN Jaguars is our maximum (at least when using the serial connector).

[Jefferson]

We use C++.
After posting that comment, I did some digging and found a post from bob.wolff68 with some examples from the Janksters. Here it is:

http://www.chiefdelphi.com/forums/sh...87&postcount=2

Nice, easy implementation of tasks there. Got it running last night to monitor a digitial input that was changing too quickly for the command to reliably catch.

[brennonbrimhall]

Team 20 has had lots of ups and downs with CAN over the last two years too.

From a programming standpoint, CAN commands are routed through several different plugins from the cRIO to the Jags themselves, depending on what language you use. Some teams with really awesome software mentors have developed their own drivers for CAN. Maybe that's a route you want to pursue?

[Mike9966]

Well, this is anecdotal in nature, but after our competition at 10000 Lakes where we removed 3 of the jags from the CAN bus and put them on PWM, the other 8 worked very well.
Our bot drove well, and was responsive.
I would like to revisit this someday with better diagnostic tools available, but for now, I'm just going to say that for us, the max number of jags on the bus will be 8. More than that will have to go on PWM.

Thanks for all your thoughts everyone, and if I am able to better analyze this someday, I'll be sure to let you know the results.

Mike