Re: Serial to CAN Gateway in new Black Jaguars?
 

The CAN connectors are pass throughs, and do operate without power. The Jaguar does not act as a repeater.

CAN is nominally a daisy chain / trunked layout. What you are referring to is a "vampire tap", a short deviation from the trunk. The signal reflects off of the end of each of the taps, which can cause signal integrity issue if the tap is too long for the bitrate (when in the bitlength does the reflection hit)? If they are kept short and the bit rate is kept low, its a perfectly reasonable way to run a CAN bus.

We decided that it would be better to avoid the issue entirely and go with a purely daisy chained approach. This allows for a higher bit rate and is much easier to assemble and is cheaper. Also, I'm not entirely convinced that a tapped topology is more reliable; Who is going to make the wiring?

I'm not saying that tapped is universally inferior to daisy-chained. I'm just saying that it isn't appropriate for FRC.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Supply of the new Jag's wont be a problem...;) :D

Re: Serial to CAN Gateway in new Black Jaguars?
 

Hi folks,

I am happy to announce that TI and Digi-Key have rolled out the FRC2010 promotional price for the MDL-BDC (Jaguar) and the brand new MDL-BDC24 (Black Jaguar).

See you at Kick-Off in Manchester!

Jaguar Microsite - check now, check back after Kick-Off:
http://www.luminarymicro.com/jaguar

Digi-Key order link:
http://ordering.digikey.com/Promotio...mpetition.aspx

-Scott

Re: Serial to CAN Gateway in new Black Jaguars?
 

Thank you Scott.....I look forward to doing business with you again!

Re: Serial to CAN Gateway in new Black Jaguars?
 

Scott,

Can you tell us if the durability improvements that you guys added to the black jaguars are also included in the standard gray ones this year? Specifically the issues surrounding losing one direction on the Jags?

Re: Serial to CAN Gateway in new Black Jaguars?
 

Yes, that would be nice. I was wondering the same thing. I heard that because the black Jaguars can handle up to 24V, it should be better (but I don't know what the failure point in the old Jags was so this may or may not help).

Re: Serial to CAN Gateway in new Black Jaguars?
 

To add a question to the growing list here..

Since CAN is now available, does it mean we can exploit/use use encoders, and/or the Analog pins for a pot connected directly to the Jaguar?

I haven't been able to find a definitive yes or no. Hence I'm asking if anyone else has found out/determined?

Thanks

Re: Serial to CAN Gateway in new Black Jaguars?
 

In setting up our teams DS and such I noticed on the FRC updates page of WPI there is a link relating to the CAN network. The information was supposed to be available already but it isn't. I would take a guess that alot of the questions regarding its usage this year will be in there when it gets released.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Michael,
<R60> The control system is designed to allow wireless control of the ROBOTS. The Classmate PC, FirstTouch I/O module, cRIO-FRC, speed controllers, relay modules, wireless bridge, batteries, and battery charger shall not be tampered with, modified, or adjusted in any way

L. If CAN-bus functionality is used, limit switch jumpers may be removed from a Jaguar speed controller and a custom limit switch circuit may be substituted (so that the cRIO-FRC may read the status of the limit switches).

I will need to investigate this as I thought the limit switches were direct inputs to the speed controller micro. This rule implies that the CAN bus must read and process the status of the limit switches.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Al,

While that addresses whether limit switches may be connected to the Jaguars it does not address whether we may connect potentiometers to the analog input or encoders to the encoder input on the Jaguars.

<R68> says sensors or other custom electronics may be connected to the CAN bus, but does not say they may be connected directly to a Jaguar. This connection method is necessary to utilize the position or velocity control modes of the Jaguar.

Re: Serial to CAN Gateway in new Black Jaguars?
 

I previously recall someone mentioning that both pwm an CAN cables had to be connected to a jaguar for a heartbeat message. It sounds to me like this isn't the case.

My interpretation: Since a Jaguar is a CAN node on the CANBus....anything connected a port on the Jaguar is now on the CANBus.... which is allowed.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Tony and Kevin,
Our posts seems to raise more questions. I however read Sec. 8 as the only allowed inputs to a Jag are the limit switches. Other sensors that have a CAN bus interface are allowed to live on the bus to be used by the Crio to interpret and provide command to the bus. It would appear in the way the rules are written, that the Crio is to be the only command device for motor control. A quick glance through the Jag documents does not suggest that sensor inputs to the Jag are echoed out onto the bus. They are simply used by the internal controller to affect the output to the motor.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Although I can not speak for the GDC, my interpretation is that encoders and potentiometers are allowed to be used with the Jaguars. My recommendation is to:
1) Move forward under the Yes assumption
2) Have a back-up plan
3) Ask the question.

Re: Serial to CAN Gateway in new Black Jaguars?
 

You have at least received the Black Jaguar? Our team not! :mad:

Re: Serial to CAN Gateway in new Black Jaguars?
 

The connection of both CAN cables and PWM cables is only necessary if the CAN bus is being spoken to through an "untrusted" interface -- one for which a "trusted" driver is not being used. The definition of "trusted" here is more-or-less a driver that is certain to be obeying the enable/disable signals and can inform the Jags that it is doing so. If the Jags are not informed that the CAN messages can be "trusted" then it will require the PWM heartbeat.

At the moment, the only "trusted" driver that I am aware of is that which uses the serial port on the cRIO and assumes it is connected to a black Jag as a serial->CAN bridge. See http://firstforge.wpi.edu/sf/frs/do/....canjaguar/frs

All that said, the rule as written seems to deny the use of "untrusted" CAN. I obviously do not know if that was intentional.