Advantage of CAN?

[nickpeq]

I can't seem to find much information on CAN Jaguars. I bet the information has been right in front of me, but it's about time for me to ask for help.
I've only worked with PWM Jaguars so far. I'd like to know what advantages CAN has over PWM. Do I have to use CAN to use Encoders? I see that the javadocs show a getRate() method for the Encoder class. Can I use that just as effectively without switching over to CAN?

[Cecil]

You can use the encoders using 2 digital inputs from the Digital Sidecar just fine, without using CAN.

As far as advantages, the main one that I personally like is no more zip tying PWM wires together to run them across the robot several times. With CAN, the Jaguars can be daisy chained together, making it look a lot cleaner and easier to find faults.

[The Lucas]

One often overlooked feature of the CAN is the ability to change from ccoast to brake mode on the fly. Every year it is a requirement for our robot drive to use brake mode in auto mode for precision and in coast mode during teleop so the driver doesnt flip the bot. Before CAN we had to waste 2 precious digital outputs and make annoying custom daisy chain cables to change the brake coast header. Now it is simply another CAN command.

[otherguy]

Originally Posted by nickpeq

I can't seem to find much information on CAN Jaguars. I bet the information has been right in front of me, but it's about time for me to ask for help.
I've only worked with PWM Jaguars so far. I'd like to know what advantages CAN has over PWM. Do I have to use CAN to use Encoders? I see that the javadocs show a getRate() method for the Encoder class. Can I use that just as effectively without switching over to CAN?

No you don't need to use CAN to use encoders. Using CAN would allow you to wire your encoders directly into your Jaguar instead of the cRIO.

If you plan on using any of the closed loop control features of the Jags, make sure you do your homework up front... people haven't had the best luck getting reliable closed loop control out of the Jags. [read more]

For more info on CAN check out my team's tutorial on the subject:
team2168.org/index.php/resources/electrical/210-can-jaguars

[duane]

Originally Posted by Cecil

As far as advantages, the main one that I personally like is no more zip tying PWM wires together to run them across the robot several times. With CAN, the Jaguars can be daisy chained together, making it look a lot cleaner and easier to find faults.

To further extend this description, CAN has positive locking connections. We've always experienced problems with getting PWM connectors to stay connected.

[juchong]

The biggest advantages we've noticed while using CAN have been current/voltage monitoring and feedback as well as the ability to use the jags directly with encoders. If it weren't for this feature, drive systems such as crab drive would be very difficult to pull off using the DIO on the cRio. Everything would be way too slow to be usable.

That being said, there are limits. If you have too many CAN devices on the bus and are not using a 2CAN controller, then you'll run into problems. But if you're working with 2 steering jags and a bunch of drive jags on PWM, the system is plenty fast. Another issue is being forced to understand what PID is and how it works. Many teams are not familiar with the underlying theory and find it difficult to work with the jag's built-in PID.

I also agree with Cecil, wiring is much easier too.

[Ether]

Originally Posted by juchong

the ability to use the jags directly with encoders. If it weren't for this feature, drive systems such as crab drive would be very difficult to pull off using the DIO on the cRio. Everything would be way too slow to be usable.

Is 10ms too slow to get responsive closed-loop control of wheel steering angle?