Serial to CAN Gateway in new Black Jaguars?

[Gdeaver]

I believe that the serial-CAN implementation does not allow on the fly choice of Can or PWM. The PWM cable provides a heart beat since the jags are operating in untrusted mode. Also my understanding is that there is a different C-RIO FPGA image for can vs PWM control. There are some good threads on Chief Delphi and the First Beta forum on the CAN situation. Also, Luminary Micros have documentation that can be downloaded. 1 week to go until the kick off. Much should be reveled then. In the mean time if a team is considering using CAN, do some homework now. If the serial rate is 115k then there could be update rate concerns especially if there are many jags on the bus. It's not the bit rate alone, Have to consider latency issues. I can remember Dave giving a warning about serialized communications last year when the new controller was being speculated on. I would definitely head his warnings. The serial and Ethernet Can solutions both allow experimentation with out the C-RIO and the driver station by directly communicating with a PC. This brings up safety concerns because there is no E-STOP button in the loop. BE SAFE.

[s1900ahon]

Originally Posted by Gdeaver

Also my understanding is that there is a different C-RIO FPGA image for can vs PWM control.

Same FPGA image. The cRIO FPGA is unaware of CAN.

BE SAFE.

Absolutely.

[Kingofl337]

In C and Java all you need is to kill the Instance of CANJaguar and Construct PWMJaguar. You will also have to let your code know not to use the advanced features in fail safe mode. I will double check with Brad to see if this will work.

Edit: Also on Al's note, I'd go as far to say if you can't run your robot for 4 minutes on a battery it may spell trouble. especially with the MK batteries. If your team grabs a weak battery and your on the edge of power consumption you may find yourself dead on the field at a critical point. It stinks to loose a key match to a weak battery.

[Tom Line]

Originally Posted by Kingofl337

In C and Java all you need is to kill the Instance of CANJaguar and Construct PWMJaguar. You will also have to let your code know not to use the advanced features in fail safe mode. I will double check with Brad to see if this will work.

Edit: Also on Al's note, I'd go as far to say if you can't run your robot for 4 minutes on a battery it may spell trouble. especially with the MK batteries. If your team grabs a weak battery and your on the edge of power consumption you may find yourself dead on the field at a critical point. It stinks to loose a key match to a weak battery.

Regarding the weak battery - it depends.

During overdrive, many teams were pushing the batteries VERY hard. So hard that during the practice matches, they were dieing at the end. This includes a number of top teams. I had the luck to watch the battery voltage on one of the world champion teams during a regional competition, and at the end of the 4 minute period they were in the 6's and 7's voltage wise while trying to hurdle.

I know we would never have made it through 2 matches without performance degragation. We started to lose simultaneous lift + drive ability after 3 minutes. (4 cims + 2 fish running near stall during the lift + turn).

That's why we rank all of our batteries on a battery tester (the one Al recommended I believe) and only use the top ones at regionals.

[dmcguire3006]

This thread has gone incredibly off-topic, which is good because I have learned a lot that would never have occurred to me otherwise (mostly about batteries in competitions). I would like some specific information on battery testers, such as manufacturers and costs. I think qualifying your batteries before a competition is an excellent idea. Does Al still recommend this one:
http://www.westmountainradio.com/CBA_ham.htm

Thanks again for the all of the valuable info.

[Tom Line]

That is the one we bought. It seriously opened some eyes when we used it - batteries that we thought we ok tested horrible, and a battery from 2+ years ago tested as our best !

Very helpful and highly recommended. I never did thank Al for the great recommendation.

[Al Skierkiewicz]

Originally Posted by dmcguire3006

Does Al still recommend this one:
http://www.westmountainradio.com/CBA_ham.htm

Thanks again for the all of the valuable info.

Yes.
West Mountain also sells a higher current device for those who wish to test at really high currents. I would recommend a high current test be carried out only once or twice a season. We also save the battery tests to a file and overlay the battery with a new test next season.

Please remember that even under the best conditions, the manufacturer specs the battery at 400 charge/discharge cycles. I would guess under our use, that is 300 for teams with the two match or better usage and 200 or less for those that drain a battery in one match.

[ajlapp]

Are the CAN connectors on the Jaguars able to pass data through if they have no power. Are they simply unions or is the Jaguar doing something with the info?

From my experience with automotive CAN bus layout, we always have a main trunk with a terminator. Each CAN device then has a direct link to the trunk...nothing is daisy-chained. Would this help eliminate failure concerns, excluding losing the main Black Jaguar or the trunk line?

[EricVanWyk]

Originally Posted by ajlapp

Are the CAN connectors on the Jaguars able to pass data through if they have no power. Are they simply unions or is the Jaguar doing something with the info?

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

Originally Posted by ajlapp

From my experience with automotive CAN bus layout, we always have a main trunk with a terminator. Each CAN device then has a direct link to the trunk...nothing is daisy-chained. Would this help eliminate failure concerns, excluding losing the main Black Jaguar or the trunk line?

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.

[www.divsys.com]

Supply of the new Jag's wont be a problem...

[utlinebacker]

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

[Jon236]

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

[Tom Line]

Originally Posted by utlinebacker

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

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?

[Eugene Fang]

Originally Posted by Tom Line

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?

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).