Legality of the 2CAN

[Geek 2.0]

I'm interested in using the 2CAN on our robot this year, however, the rules state that ethernet-to-CAN interfaces need to be on Ethernet Port 2 (R64), whereas the 2CAN is meant to go in between the Wireless Bridge and the cRIO (as far as I understand). Does this make it illegal?

[Paul Copioli]

This is Mike Copioli, The 2CAN can connect to either port 1 or port 2 on the cRIO therefore it is legal for use this year when connected to port 2.

[Geek 2.0]

Does that take away the ability to use the camera? I would assume not, because it has an ethernet switch built in, but I just want to make sure.

[Paul Copioli]

Yes, you are correct, you will still be able to connect the camera or any other Ethernet device that is deemed legal.

-Mike Copioli

[woodk]

Is there going to be a functional update to the firmware, and example C++ code for how to use the 2CAN? If so, when can we expect it?

- Kevin

[Mike Copioli]

A plugin will be released shortly that will enable the cRIO to use the 2CAN as the CAN gateway in in the same manner as the black Jaguar plugin. An outfile will be provided at FIRST forge http://first.wpi.edu/FRC/frcupdates.html. I will post on CD when the plugin is released. A firmware update will be released at the same time.

[Akash Rastogi]

Mike,

I'm not too great with understanding this CAN stuff, but when the Jags are linked up, if a failure occurs in any of the Jags, does that effect the function of the others in the series? I'm not exactly sure how it works.

[Mike Copioli]

Originally Posted by Akash Rastogi

Mike,

I'm not too great with understanding this CAN stuff, but when the Jags are linked up, if a failure occurs in any of the Jags, does that effect the function of the others in the series? I'm not exactly sure how it works.

This is an excellent question. There is more than one answer. In order to address each case we will need to look at the different methods of failure. Lets start with the known failures that have been seen last year.

- The jaguar looses control in one direction.
looking at the schematic and layout of of the Jaguar you see that the CAN bus traces connecting the CAN connectors are continuous that is they run directly from one to the other without any interruption or component placement. They are continuous pieces of copper. In this failure scenario the CAN bus would not be affected.

- Jaguar losses power due to failure or improper wiring methods.
Since the CAN traces inside the Jag provide a pass through, this would not cause a loss of the bus.

- A CAN connector becomes disconnected from one of the Jaguars.
This is a complicated one to answer. In short this will cause a failure. However the failure could be isolated to the Jaguars that are connected downstream of the failure. Although the termination resistor has been removed from one end of the bus it does not guarantee failure especially on shorter buses. A possible preventative measure would be to use what is known as parallel bus or as Eric Vanwyck called it a "Vampire Tap". This type of connection requires more attention to cable length due to a property known as signal reflection. Basically all of the Jags and other CAN nodes would attach to a harness instead of being connected in series using the CAN connectors on the JAG. This is the type of connection used in the automotive, aerospace and other industries.

I hope this answers your question.

[Akash Rastogi]

Originally Posted by Mike Copioli

I hope this answers your question.

Definitely! Exactly what I wanted to know. Thank you.

[Mike Copioli]

A plugin is now available for the 2CAN.

http://www.chiefdelphi.com/forums/sh...highlight=2can