Serial to CAN Gateway in new Black Jaguars?
 

It appears that the new Black Jaguar Motor Controllers are capable of interfacing with either a standard serial port at at bit rate of 115.2 kbps, or a Controller Area Network (CAN) interface. See the data sheet available at: http://www.luminarymicro.com/products/mdl-bdc24.html (don't bother to register, just select "OPTIONS"). It seems that the Black Jaguar can act as a Serial to CAN gateway to all of the motor controllers in the system. This implies that a single serial port on the cRIO will be able to control all of the motors on the robot, getting rid of the pesky requirement for a $1000 CAN interface module on the cRIO. It also implies that a single Black Jaguar in the system can act as a CAN gateway to all of the older Tan Jaguars that we already have. This will give us access to to motor current and voltage, and the built in quadrature encoders. In the data sheet it actually says that the Black Jaguar "Directly interfaces to a PC serial port or National Instruments cRIO".

My question is to those cRIO people out there: Do we have access to the serial port on the cRIO, or is already being used for some other function (debugging or diagnostics) in the system?

If the serial port is available, I see no reason why everyone shouldn't be using the CAN interface this year.

Thoughts?

Re: Serial to CAN Gateway in new Black Jaguars?
 

In following the beta forums(as a team that helped out as part of one of the teams that was part of the labview beta and not a hardware beta test team) it sounded like the cRIO serial port is the planned way of interfacing with the new Jags and then the new jag would act like a bridge to the old jags. as of right now the serial port is only being used for diagnostic data if i understand correctly.

Again the thing to always keep in mind is that just because it is being tested as part of the beta this year doesn't mean that the GDC will actually allow the use of CAN for the competition this year.

Please anyone else please pipe up and correct me if i'm wrong on this.

Re: Serial to CAN Gateway in new Black Jaguars?
 

http://www.chiefdelphi.com/forums/sh...ad.php?t=78632
http://www.chiefdelphi.com/forums/sh...ad.php?t=79076

Re: Serial to CAN Gateway in new Black Jaguars?
 

The First forum has a couple threads discussing this. Note the comment about the can being run in untrusted mode requiring a PWM cable and can cable to each jag. Also of concern is that Digikey only has about 1000 black jags. With veteran teams only getting 2 in the kit, If every team ordered 2 jags then there would be a supply problem.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Could you give me a link to the posts on FIRST forums? I couldn't get anywhere searching "CAN", "Jaguar" or "untrusted". Thanks! Also, keep in mind, only one Black Jaguar would be necessary per robot to act as a Gateway to last year's CAN enabled TAN Jaguars. Digikey currently has 780 Black Jaguars (MDL-BDC24) in stock.

One more quick observation - the Black Jaguar CAN gateway makes the 2CAN Ethernet to CAN converter a more expensive solution than just purchasing a DB-9 female to RJ-11 adapter (http://www.trianglecables.com/modular-adapters.html) and using the serial ports to run/monitor the motor controllers.

Re: Serial to CAN Gateway in new Black Jaguars?
 

d et al,
Remember that although the jaguars had CAN last year, the rules did not yet allow it to be used. Please hold your ideas until kickoff when you will know for sure.
From a personal standpoint, a daisy chain loop of control signals does provide a single point failure for all/most/some robot function.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Also, remember that the Jaguar is a piece of TI's advertising strategy. Professional Electrical Engineers can use the Jag as a "getting started" evaluation kit for ARM core that powers it. Therefore, it is in TI's best interest to cram as much awesome as possible into it, even if the GDC doesn't want to enable the awesome.

The 2CAN has a couple of cool features that a serial enabled black Jag doesn't. It will be up to teams to decide whether or not they justify the cost.

We all have to wait to see what the rules allow, but I'm certainly excited.

*EDIT: Like bandwidth!

Re: Serial to CAN Gateway in new Black Jaguars?
 

TI's purchasing Luminary Micro never has made a whole lot of sense to me. It's not like TI didn't have the expertise to license the ARM core and program it themselves. I think that they are more focused on the power MOSFETs which is probably the largest part of the real cost of the Jaguar controller, rather than the microcontroller and associated programming.
http://focus.ti.com/general/docs/gen...ontentId=53265

That being said, they do make a big deal about the serial enabled nature of the Black Jag in the literature developed specifically for FIRST. I think that I'll buy a couple and the DB-9 to RJ11's and have one of my team members investigate the interface just on a hunch.

Thanks for everyone's input.

Re: Serial to CAN Gateway in new Black Jaguars?
 

It sounds like you think TI acquired LMI for the purposes of Jaguar. It didn't. TI's acquisition of LMI was for all of the microcontrollers (MCUs) that LMI developed and were selling (plus the eval kits plus the software that accompanied the eval kits, etc.). TI acquired a catalog MCU business that complements their existing MCU offerings (C2000 and MSP430).

The Jaguar speed controller is a design example of how to use one of the MCUs in a brushed DC motor control application.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Luminary doesn't own the ARM processor. ARM does:
http://www.arm.com/products/licensing/

I could license the core and (with enough funding) become a fabless production house tomorrow. TI wants to sell silicon and the best way to do that is MOSFETs.

No sense in buying a processor that they will have to license through ARM anyway. imho.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Does the Jaguar RJ-11 port speak RS232? I thought those were CAN ports; CAN protocol is not compatible with RS232 on several levels without some intelligence in-between.

Am I misunderstanding something here (I frequently do)?

Re: Serial to CAN Gateway in new Black Jaguars?
 

One of the two RJ11 ports has speaks RS232 on two of the previously-unused lines. Therefore, that port can either extend the CAN chain, or act as a bridge.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Looking at a new black plastic Jaguar from the front (connectors) the right connector is 6P4C and is for CAN only and the left connector is 6P6C and is for CAN and RS232. The inner four contacts on both connectors are the exact same. The outer two contacts on the left connector are RS232.

On a grey plastic Jaguar, both connectors are 6P4C and are CAN only.

Re: Serial to CAN Gateway in new Black Jaguars?
 

You can find semi-full descriptions of the new CAN and how it is used on the First Beta Forums here:

http://forums.usfirst.org/forumdisplay.php?f=1260

This is one of the things the first teams have been beta testing: you will find forum posts, presentations, and descriptions on how they work.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Sounds like a done deal. I'll bet that there is one of these in the KOP:
http://www.computercablestore.com/Mo..._F_PID948.aspx

As well as some of these:
http://www.dataaccessories.com/rj11.html

Communications protocol is here:
kamocat.com/Jag/SW-RDK-BDC-UG-4201.pdf

As far as CAN being a liability because of single point failure (as opposed to independent PWM line), I'm sure that no one has built in redundant motors so the net result on a cable failure would be the same between CAN and PWM.

Good thing about CAN is that you can monitor motor voltage and current and hence computing a running energy expenditure tally would be quite simple.

Energy = Power*Time = Voltage*Current*Time

Suggesting that this year's game may be about keeping track/minimizing energy resources in pursuit of a more general goal. This allows FIRST take a quantum leap in relevance.

Re: Serial to CAN Gateway in new Black Jaguars?
 

This depends on what motor is connected to the controller with the failed cable. If a drive motor PWM fails, odds are it's the same, but if a manipulator PWM fails then the robot could still drive with PWM, but with CAN you're dead in the water.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Actually, there are some very significant differences between the failures. If you lose a PWM cable used in the traditional configuration (and honesty, there are probably very few teams that have NOT had a PWM that came loose or someone forgot to plug back in at one point or another), at most you lose one motor. In almost every case, the robot is still operable, although with reduced functionality. If you lose a CANbus cable, or have a single device at the head end of the bus catastrophically fail, you can lose access to every motor connected to the bus.

The risks associated with these two options are substantially different. Whether the risk profile is a reasonable trade given the benefits that come with the use of a CANbus configuration is something that each team will have to assess for themselves. Based on your tolerance for risk and your ability to take advantage of the added capabilities of CAN, this trade-off may or may not make sense (personally, I think that for most teams it certainly will make sense, and I would expect to see a lot of teams using the CANbus configurations this year - they just need to understand the risks of doing so).

-dave




-

Re: Serial to CAN Gateway in new Black Jaguars?
 

You can also add fault tolerance in you code/wiring, and with the flip of a switch go from CAN to PWM as a fail safe mode.

Re: Serial to CAN Gateway in new Black Jaguars?
 

I'm not sure it will be quite that easy - no one except the can-beta teams have played with the CAN code that has been written for this year.

In addition, remember that CAN will not be officially supported (even if it IS legal to use).

Re: Serial to CAN Gateway in new Black Jaguars?
 

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

D,
Dave has covered the single point failure response so I won't add to that. Computing energy usage as you suggest may be a little more difficult than you expect. Current spikes and voltage dips occur in short pulses that require frequent monitoring in order to be accurate. To spend a great deal of time gathering data and totaling the same may actually reduce your effectiveness in driving and accomplishing game goals. Should your samples occur at the rising or falling edge of a pulse and you were to calculate energy remaining on such data, you can imagine the result. Dependent on the load, motors draw full stall current each time they start. That current may be sustained over several brush commutations dependent on the motor in use or it may be present for a significant length of time. At any rate, there are other variables that come into play which would interfere with your calculations that are not monitored by the can bus. The most significant in my mind is battery temperature and it's effect on internal battery resistance and output current capability.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Since the A/d converters for the Voltage & Current sensing are embedded in the MCU, and since they are sampling at 15Ks/s (see data sheet), and hoping that the design engineers applied appropriate lowpass filtering before the A/D converters, I don't thing that the erratic nature of voltage & current will be a significant factor. I did notice that the accuracy of reading voltage is +/-.3V and +/-1A, meaning the accuracy in power measurement in 0.3 Watts, but this should be insignificant given the average power consumption of the robot would be approx 300W.

Another advantage of CAN is this mode (from the Black Jag data sheet):

"Position Control Interface
This set of commands is used to configure and operate the motor controller using position control mode. The motor control position commands consist of enable/disable of position mode, setting the motor position, setting the PID loop control parameters and setting the source for detecting position. Position control is managed through the use of an externally attached optical encoder combined with the motor controller’s encoder inputs or through the use of a potentiometer."

So it looks like the CAN interface can make the CIM (or whatever) motor, attached to an position encoder or potentiometer, operate as is it were a servo: the user can command the angular position and the Jag will close the servo loop to seek to the desired position.

Re: Serial to CAN Gateway in new Black Jaguars?
 

D,
I was referring to the amount of data that would need to pass through the buss from each controller and the CRio. Those reading this thread should also remember the switching frequency of the controller is 15kHz and is not synchronized with other controllers. Pulses of high current do last considerably less than the rep rate for switching and data samples in some cases. Also designers need to correlate data with discharge rates on the battery. High current demands reduce the capacity of the battery significantly but with the variable nature of a match, one can only guess at the effect on battery life vs. current usage.
I can give you some data on first hand observation over years of play. Some teams will completely drain a battery in a two minute match (2009 excluded). Some teams will draw down the terminal voltage of the battery enough to interrupt voltage supply to the gaming adapter and/or the Crio causing some loss of game play while systems reboot. Some designs are more critical of battery operation and some designs will produce loads in excess of 400 amps in turns on carpet. All designs will draw near max current in a pushing match or when a driver is lodged against the field borders. There exists enough resistance in most designs to discount power readings at the controllers from being used to predict battery life.
And finally, Al's Rule of Thumb for robot design (derived from observation)...If your robot can't play at least two matches on one battery, your mechanical design and/or driver strategy needs some rethinking.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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

Absolutely.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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 :eek:!

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

Re: Serial to CAN Gateway in new Black Jaguars?
 

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

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?

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.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Trusted mode and untrusted mode are no longer necessary. The current Jaguar firmware expects a "token" when sent a throttle request via CAN. This token is generated by the cRIO. If the CAN frame setting throttle does not contain the token the Jaguar sets its output to 0. This latest implementation allows teams to create there own CAN nodes without having to use PWM cables and allows teams to generate CAN frames over Ethernet.

-Mike Copioli

Re: Serial to CAN Gateway in new Black Jaguars?
 

My interpretation of that is that the Jaguars can only receive signals over one medium or the other (CAN or PWM). I believe that this means they can both be used, like CAN for a primary controller and PWM signals as a backup if for instance your Black Jaguar dies and you no longer have a convertor. That would still allow for operation of other motors if you can detect the loss of signal.

Just my interpretation, I would suggest a Q&A be posted about this point thought if this is actually going to be used.

Re: Serial to CAN Gateway in new Black Jaguars?
 

I think the rules are pretty clear. CAN or PWM - choose one.

As Mike said, the "both" option is vestigial and not legal for 2010. This is actually a boon, the "both" option is ugly to be honest.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Team Update #1 has clarified the issue of connecting sensors directly to the Jaguar inputs.

It is now legal to connect sensors or custom circuits to the Jaguar inputs per rule <R68-H>

Current mode ... or any mode other than voltage
 

Has anyone got current mode to work on the jaguars?

Or any other mode other than voltage?

I got it running from a PC using the bdcomm (I think its called) app. However, the c++ code supplied only supports voltage mode. I've been trying to modify it to add other modes, but no success yet.

- Kevin

Re: Current mode ... or any mode other than voltage
 

What does current mode do?
I know that the jaguar can adjust the amount of current drawn through pulse-withing the motor power, but is it running at full speed during that time?
I have only tried experimenting with the voltage control mode at this time, but the low speed control (over CAN) seems to be much better then before.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Kevin,
The Jaguar controls average current by pulse width modulation but the pulses can only go between 0 volts and the battery terminal voltage (12 volts nominal.). Are you thinking of current sense? That is available through the CAN bus. There is a series resistor built into the Jaguar and the voltage drop across that resistor can then be used to calculate current through the device.

Re: Current mode ... or any mode other than voltage
 

Current control mode allows users to servo the output of the Jaguar to a given current. PID gains can be set to change the Jaguars response to changing conditions. The maximum current that can be obtained if finite and determined by several factors including the maximum output voltage and duty cycle of the Jaguar.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Are the black jags (MDL-BDC24) legal this season. Where is this referenced? and what are the advantages.

Re: Serial to CAN Gateway in new Black Jaguars?
 

Under this rule for starts...
<R42> Items specifically PROHIBITED from use on the ROBOT include:

D. Motor speed controllers other than Innovation First, Inc. “Victor 884” speed controllers or Luminary Micro/Texas Instruments “Jaguar” (MDL-BDC or MDL-BDC24) speed controllers,

You will also find reference to the Black version needing to be the first in line when using the CAN bus.