pic: cRIO CAN Jag
 

Re: pic: cRIO CAN Jag
 

Very cool. I'm crossing my fingers that this is a "go" for 2010...

Re: pic: cRIO CAN Jag
 

I like how they just left the head of the cable in the last jag (:

Thats really cool. daisy chained jag's look intimidating without those silly 3-color wires coming out of them.

Re: pic: cRIO CAN Jag
 

Does the idea of having (potentially) all of your speed controllers in series scare anybody else?

One would assume that the CAN pass through circuitry is sufficiently removed from the motor driver so that even a "blown" Jag wouldn't bring down the entire network. Even if that is the case it seems like this configuration could lead to a really tough time debugging your electrical system.

Re: pic: cRIO CAN Jag
 

Look at it closely. I'm pretty sure that's a termination resistor, something typically used to suppress signal reflections at the end of a high-speed bus like CAN.

Re: pic: cRIO CAN Jag
 

Eh, not really. CAN is reasonably fault tolerant. I'd be more afraid of a cable coming out or a device on the bus going "babbling idiot mode" than one Jaguar electrically disabling others.


Quoted for Truth. Standard CAN usually has 120 Ohm termination resistors on either end of the bus.

Re: pic: cRIO CAN Jag
 

THe only thing that worries me is all those RJ45 connectors in series.....you saw what happened to similar connectors on the DS this year when used in a competitive environment.

Re: pic: cRIO CAN Jag
 

Well, ideally your electronics would be in a low impact area on your robot, right?

-Nick

Re: pic: cRIO CAN Jag
 

Yeah, right :)

Re: pic: cRIO CAN Jag
 

Finding a low impact area is difficult to do in the situation where a 150lb robot going 12fps slams into your bot.

If anything we can do the clear nail polish thing again. It worked wonders on the IFI PWMs and it still works great on my R/C car.

Re: pic: cRIO CAN Jag
 

Unfortunately the RJ series connectors are inherently flaky....

Re: pic: cRIO CAN Jag
 

Please don't assume that because KwikByte chose to use an unacceptably inferior component that TI/Luminary did as well. RJ connectors come in many forms and many quality levels. If you squeeze cost out hard enough, any component can become a failure point.

Re: pic: cRIO CAN Jag
 

In my opinion, I hope they release the module before season so we have a few week to play with it. Even though none of our pwm's ever came out, I personally would feel better if we used CAN.

-RC

Re: pic: cRIO CAN Jag
 

What I like about CAN is removal of several PWM wires all traveling the same path and having to check which pin number it was in and verifying correct orientation on both ends several times during the build when things would get disassembled and reassembled. With CAN, 1 RJ45 cable from the cRIO from just the CAN bumper to the first device and then daisy chain from there. No need to verify orientation and keep the log of which pin to which device ... all that is in the code and addressing log.

How many times did your robot temporarily lose functionality after a re-build because a PWM was not inserted into the correct pin ...:ahh:

Re: pic: cRIO CAN Jag
 

Unfortunately, cost seems to be the primary design consideration for the RJ series since it's inception decades ago.

Hopefully Luminary has figured out how to make the system reliable....but my long experience with the connector series isn't good.

Re: pic: cRIO CAN Jag
 

Please cite your source ...


... and compare the 'flaky'ness to the 3 pin non locking PWM cables we've used in the past.

Re: pic: cRIO CAN Jag
 

My source is 35 years of playing with electronic stuff.

The PWM cables are not wired in series.....the CAN bus is a daisy chain. Any one poor connection can kill the rest of the chain.

Re: pic: cRIO CAN Jag
 

The saying 'You Get What You Pay For' comes into play with RJ connectors. If you want reliability you're going to pay for it.

Re: pic: cRIO CAN Jag
 

I hope some time and money is being invested in to the short commings of the jag. Next year we may be back on carpet and It's my opinion that the are several points of failure that could cause some serious problems when first teams start to abuse them. I would rather have a solid Hobby PWM jag that is robust than a weak can jag.

Re: pic: cRIO CAN Jag
 

From my rudimentary knowledge of CAN bus topology, I believe the Jags can be arranged in a ring, thus providing some connection redundancy. The Luminary folks at Championship thought this could be done as well. Does this make anyone sleep better?

Re: pic: cRIO CAN Jag
 

Yes, that would be good....

The thing about connectors is: Good connectors have both a positive mechanical connection for the housing (the housing halves cannot be pulled apart without first releasing something), and a positive pressure contact connection (the pin is encased in the socket). The PWM cables lack the housing lock, and the RJ series has only a single side contact.

Re: pic: cRIO CAN Jag
 

Wait, our robots have low impact areas? How did I miss this? :p

With all seriousness, daisy chaining these makes me want to mount my electronics on shock mounts.... Just in case, y'know?

Re: pic: cRIO CAN Jag
 

Well, in his presentation in Atlanta, Al Skierkiewicz mentioned that WildStang uses zip ties to secure their controllers to allow quick swapping. The controllers would not be as rigidly secured compared to using 4-40's and thus be able to absorb shocks.

Re: pic: cRIO CAN Jag
 

If you think the RJ-45 connectors are going to be a problem you can still use the 3-pin molex if you want to...

This year, we made a nice little electronics box near the end of build season because our electronics boards had begun to look like we'd planted a wire bush and it grew. We ended up with our electronics vertically mounted on 1/8" Lexan with another piece of 1/8" Lexan on the outside to shield them. The only connection problem we had was the ethernet cable coming out because we hadn't checked to make sure it clicked before we went on the field (we'd been doing some tethered debugging). All of our Jaguars were on 1/4" mounts with two Jaguars per mount, so they were able to flop around a bit. The whole thing provided enough rigidity for nothing to break and enough flexibility that no shocks were conveyed directly into any components. Same type of system should work well for RJ-45, because the two Jaguars per mount would be easy to attach to, and then you have the two cables going to and coming from that mount that you can tie down in cable ties.

I'm not really worried about these connectors. We used them this year to carry the signal from our encoders to our digital breakout board and we used the little phone line couplings to change over between wires so we could replace them in segments. Since we were using swerve drive, after a couple of trips around a rogue wheel, the hot glue we used to mount the coupling popped off, and one of the encoders lost the connector on its board (not the RJ-45). Never had any problems at all with the RJ-45 connectors. And considering the build quality of these Jaguars (never replaced one once this year), I think the connectors should be of a high enough quality that they'll serve you well as long as you take care of the cable properly and keep the Jaguars protected.

Re: pic: cRIO CAN Jag
 

We find using Velcro is perfect for mounting electronics. This year, our electronics panel was all carbon fiber made in our shop too, so it made mounting even easier.

Gee, low impact areas on FRC robots? That's an oxymoron.

-Nick

Re: pic: cRIO CAN Jag
 

Point of order: The 4-pole RJ series is an RJ-10*. Doesn't affect any other statements though.
Nope, the CAN Bus is a parallel protocol, without repeaters or gateways (generally). I would fully expect an unbroken signal path from input to output; the CAN Bus controller would hang off the side of those conductors, not in series with them.

CAN doesn't work well in series or daisy-chain, and that's not the way it is supposed to be used.

It works more like a Radio channel, where everyone hears everyone else, and indeed everyone must hear everyone else (including yourself) in order for the bitwise arbitration to work. (That is the method used to ensure that messages don't collide on a CAN Bus).

A 1 Mb/s CAN bus is a Class A bus, and definitely requires terminating resistors. Their optimal value depends partly on the chips being used, and mostly on the expected medium (type of wires).

There are many CAN Bus resources on the web, however for FIRST I don't think a detailed understanding of the physical layer will be necessary to use it at the application level.

*Also RJ-9 and RJ22 - I cannot tell from LM's data sheets which specific implementation of the 4p4c standard they have. I suspect they did it to take advantage of inexpensive (unreliable?) telephone handset cables.

Re: pic: cRIO CAN Jag
 

Thanks for the explanation, Don!

I guess I wasn't quite clear expressing what my concern was, and as usual got the terminology wrong because I'm not an expert on the subject. What I meant was that the wiring method had a bunch of RJ connectors in series. The signal has to go thru all the connectors in the chain before it gets to the end. If any fail, the signal won't get through to those past it. Is my understanding correct?

Re: pic: cRIO CAN Jag
 

Considering that in most cases you'll be plugging in your CAN bus only once when you wire your robot, I don't see a concern with the RJ series connectors. Your land line telephones are also connected with RJ series connectors and they also take a fair amount of abuse, their connections have a fairly low failure rate in that environment as well as in network systems.

As a model railroader, we use a similar connection for our data bus standards for digital command control with very few problems. It should work well.

All I can say to FIRST is... "When CAN we play?" :cool:

Re: pic: cRIO CAN Jag
 

if Im reading the tea leaves correctly . . next year, I will admit Im much better at reading coffee grounds.


I just hope that they fixed the issue where if the jags sensed a 6v drop ( for any length of time) it would power down to protect itself( I can replace a bad jag, I cant replace a bad match).

Re: pic: cRIO CAN Jag
 

That sounds like a false dichotomy to me. Every indication is that the CAN bus was fully functional this year. Whether or not NI implements CAN hardware, NI or WPI write drivers for CAN, or the GDC allows CAN should be completely independent of the time Luminary Micro spends to improve the design. I haven't seen anything to indicate that Luminary Micro isn't taking the problems seriously.

Re: pic: cRIO CAN Jag
 

Erm ... power management?

Re: pic: cRIO CAN Jag
 

The 2009 game did not stress test the Jag. If First opens up the Can control there are very many issues that come into play with serialized control. With the Can control software pallete there are many ways First Teams could place the Jags into a very stressful situation. It would be nice to Know that the Jags are redesigned and robust before opening up the Can can of worms. The build season is short and the thought of battling controller failures and firmware issues should worry the people who will have to deal with product support. The motor controllers are a key piece to the system. They have to be rugged and reliable. I know everyone wants the Can stuff but, sometimes a conservative roll out can be in everyones best interest.

Re: pic: cRIO CAN Jag
 

"Clear nail polish thing"? please explain.
Thanx

Re: pic: cRIO CAN Jag
 

Clear nail polish can be used as a light glue just to hold the connector in place until you want it to come out. Unlike super glue, that last part still works.

Again, if opening up the CAN protocol worries you, use the PWM connector.

Re: pic: cRIO CAN Jag
 

This last point does need some consistent reminding even for me, more so since I am a veteran mentor since 2001. FIRST has given us options like we've not had before. Tone down the dooms day mentality a bit. There was a day when all we could use was PBasic and items found in the Small Parts Catalog. These are not bad products or vendors at all but when one now looks at the options we have:
Labview, C, Java
PWM, CAN "maybe"
AndyMark.biz, IFI Robotics, BaneBots, FRC Teams operating as LLC ...
Be cautiously prudent or dare to experiment with contingency plans::safety::

Re: pic: cRIO CAN Jag
 

As an additional point of interest:

Keep in mind that your program will need to send the data to a specific address on the CAN bus, so that means that each of your speed controllers will need a unique number... can you guess where this is going?

If you need to replace a speed controller on your can bus, you will need to do one of 2 things, either program your new speed controller with the old ones address, or determine the address of the new one (its not imprinted on it anywhere) and change your code.

Its one of those rock and a hard place problems.

Also, as a network engineer, and working in IT for 8 years now, if you use high quality connectors, and don't abuse them you shouldn't need to worry about those connectors. I have actually seen the cable come apart before the connector came out of the jack in the wall!
However If you buy your cables at the dollar / 50 cent / dumpster store good luck to you!

Re: pic: cRIO CAN Jag
 

Another separate thought.

The Jaguar controllers have built in PID control, allowing you to command the speed controller to do positive speed, positive positioning, or constant current control of your motors, as well as monitor the current, voltage, temp, etc it is currently outputting, VERY neat stuff... and only available on CAN bus... sign up for CAN bus today!!! Available anywhere CAN supplies are sold!

Re: pic: cRIO CAN Jag
 

This is by far one of the coolest posts I've seen in the past few weeks. That should be put on a poster or something.

-RC

Re: pic: cRIO CAN Jag
 

My first test of the CAN bus will be to make a CIM servo, with PID and a tough box

Re: pic: cRIO CAN Jag
 

Has anyone ordered the Design Kit?

http://www.luminarymicro.com/products/rdk_bdc.html

Re: pic: cRIO CAN Jag
 

Um, yes. I'm not sure what I was thinking, but if one connector fails, everything past that point has failed.I beg to differ. The Jaguars were indeed stressed this year - at least by our team - and were found to be rugged and reliable. Please tell us your experiences to the contrary.
That would be cool, very cool indeed. You might want to gear it down even further than a toughbox, but we'll cross that bridge when we get to it.

Re: pic: cRIO CAN Jag
 

At Atlanta, the luminary micro demo of the CAN bus was a wheel on a tough box

it was very neat to see a cim maintain a rate of 10 rpm even under heavy load

Re: pic: cRIO CAN Jag
 

Ok, I'm gonna get some n00b flack on this one, but what exactly am I looking at and how is it different than the setup we had this year??
I see the same components, & only with the addition of a telephone/modem/fax type cable added to the components similar to the way VEX uses to hook up controllers, I don't see much speculation that can come from this?

So... what's the big deal & all the fuss about?
And what the heck is CAN?
Just a little lost over here... I'm mechanical, not electrical! lol

Re: pic: cRIO CAN Jag
 

CAN is a method of communication that allows many devices to talk to each other. Think of it as ethernet, but much simpler.

PWM (as we use it) is a method of communication that allows one device to command another: One piece of information, one direction.

The advantage CAN provides is that more types of information can be sent, and it is bi-directional. This would potentially allow you to:

• Access the Jaguars back-emf and current measuring capabilities.
• Current and voltage control, rather than just duty cycle control.
• Internal PID loops
• Virtual Springs - Combine torque(current) control with built-in quadrature encoder/pot inputs.
• Active load-sharing: Have motors that share a tough-box balance their loads.
• Lots of other cool stuff.

Re: pic: cRIO CAN Jag
 

I don't agree with this, not one bit. This is like asking for the FAA-certified fly-by-wire controllers used on airplanes with the pricetag of a Jag. But hey, that's just my opinion. I've witnessed the beauty of CAN first-hand at some recent demos for work ... in the right situations it fulfills everything we ask it to, almost flawlessly. So here's my over-simplified -isms of the day. If we want to throw rapid current fluctuations and voltages changes through a motor controller that are outside the specs, it's not the manufacturer's fault. Furthermore, no matter how much the programming mentors gloat about it, software control cannot make up for bad power design without significant sacrifice to quality and/or goals.

A more probable -ism is that we shouldn't judge a motor by its size, but rather by the end results of the calculations we produce from it. CAN on!

Re: pic: cRIO CAN Jag
 

NItro had the same three motor controllers on it last year at NIWeek (first week of Aug 2008). Only back then, the plastics weren't on it. The CAN control was functional back then.

A couple of other clarifications.
1. The left-most CAN jack of the bottom Jaguar is indeed for termination. A 120 ohm resistor is crimped across the inner two contacts.
2. The CAN jack is nor RJ45, it is a 6 position 4 conductor jack (6P4C).
3. When replacing a Jaguar, an address does need to be assigned to it. This is a trivial process and can be done in seconds.

Re: pic: cRIO CAN Jag
 

Why would one order an RDK?

I don't think there is any need to order the RDK since it is intended for people/companies who want to use Jaguar as a basis of their own design. Any interesting component that is included in the RDK can be downloaded from the web site, purchased as an individual component, or made (the CAN cable).

Re: pic: cRIO CAN Jag
 

This can be done. However, the termination resistor will have to be placed elsewhere in the circuit.

Re: pic: cRIO CAN Jag
 

Done in seconds with what? And will what we use work for another team's Jaguars?

Re: pic: cRIO CAN Jag
 

You somehow initialize the re-addressing part of jags program (it will have to be part of your program on Crio) then you press the user button on the jags, first one will be addr 1, and so on

yes it will work on other teams, but you will have to re address all of them (as far as i know)

Re: pic: cRIO CAN Jag
 

Since they come from the factory as '1' it would be recommended to start with 2 and avoid 1. You are correct that the assignment sequence originates as part of some cRIO programming. Since the address is stored in non-volatile memory on the Jaguar, this needs to happen just once, but it can be changed if needed.

You only need to change the id if a Jaguar is moved to serve a different purpose for which the id is different.

Re: pic: cRIO CAN Jag
 

Scott,

I was interested in ordering the RDK in order to find out how to address the Jag's firmware. I'm sure we would be interested in your experience with this system.

Re: pic: cRIO CAN Jag
 

You can register and then download the jag software. In there you'll see abilities that the can bus can provide. The NI and WPI interface on the CRIO has not been released as far as I know.

Re: pic: cRIO CAN Jag
 

What do you mean 'address'? Update? Modify? Understand?

As Gdeaver points out, you should grab the materials included with the RDK. The same documents are downloadable from the Luminary Micro (now TI) web site. These will likely go a long way in addressing your questions.
(see http://www.luminarymicro.com/products/rdk_bdc.html).

FYI, the RDK comes with the following components...
1. A modified Jaguar. The only modification from the stock FIRST units is that the JTAG header is populated. This allows for firmware download and debug. Firmware download can also be done over CAN but debug cannot be done over CAN.
2. An interface board for debug (MDL-ADA2). This converts the small connector on Jaguar with the evaluation board (which also serves as a USB-to-JTAG interface).
3. A LM3S2965 eval board with preloaded CAN console software.
4. A small motor.
5. A small power supply is included.
6. A CD with firmware, schematics, BOM, gerbers, CAN console application, etc.
7. LM3S2965 to Jaguar CAN cable.
8. A cable that connects the LM3S2965 board and MDL-ADA2 board.

So, if you really wanted to do your own enhancements to Jaguar (say as a senior project for a EE degree - but not for FIRST legal use) you could:
a. Download the CD documents.
b. Use a stock Jaguar and solder in the header (the part number is documented in the BOM from (a) ).
c. Purchase #2 and #3.
d. Make your own #7.

Re: pic: cRIO CAN Jag
 

It looks so... PRETTY!!!!
No more PWM cables to create spaghetti.
No more PWM cables to get caught in sprockets.
No more $5 PWM cables.
No more too short $5 PWM cables.
No more too long $5 PWM cables.
No more PWM cables to make me cuss.
No more PWM cables to just come unplugged because they want to.
No more PWM cables that decide to unplug to get stuck on the 40A connections feeding the power to accelerate our robots from 0-10FPS in 1.0s flat.
No more PWM cables!!! Muaahahah!!!

Oh, but I guess a lot of the same problems exist for CAN. :yikes:

It will be a good year when this happens. This is how the real world PLC systems operate, so it's good to learn.

Re: pic: cRIO CAN Jag
 

Funny you mention an EE senior project...

For my EE senior design project, me and my group constructed a master-slave robotic arm system. The big slave arm mimicked everything the small master arm did. We used Jaguars for the motor controllers, utilizing their CAN capabilities and built in position handling.

Here is a link to several pictures and a few videos of our project (Robby was one of my group members):

http://www.robbymorrill.com/464.htm

The pictures that pertain to this thread (several pictures down the page) are not too good at showing the CAN cables. The CAN cables are zip-tied to PWM style cables that we used to connect analog encoders to the Analog ports on the Jaguars. They were very easy and cheap to make. We bought 4 conductor phone cable, 4C6P phone jacks, and a cheap crimper from Fry's, and they worked perfectly.

Here is a basic outline of our project:

1. Small master arm uses 10-turn potentiometers to measure joint angles.
2. Custom PCB using LM3S5747 (control board) measures the pots, performs necessary calculations, and sends position data to the Jaguars through CAN bus. It also controls the gripper servo.
3. Jaguars connected to control board through the can bus; daisy chained.
4. Analog absolute encoders (MA3 encoders from US Digital) connected to Jaguar's analog port (by way of a voltage divider to step 5V down to 3V for the Jag).
5. Jaguars hold position using the encoder feedback and the desired position based on the PID (Proportional - Integral - Differential) constants. (the PID constants were set by the control board via CAN)
6. 4 Globe motors and Fischer Price motor connected to 5 Jags and one VEXplorer gripper (ran out of time for our custom designed gripper).

The first video doesn't show much arm movement except for the wrist, but you can kind of see the arm move close to the end. At that point we were working on tuning our PID constants. That was probably the last time we had the arm working really well with PI (no D). While working on D we began to see a lot of nasty oscillations in the shoulder joint. This joint used to be an RS545 motor with a Banebots 256:1 P60 gearbox. Despite Banebots hardening the shaft and the sun gear, it still deformed, creating a lot of play in the gearbox. The PID oscillations and the play in the gearbox lead to the motor eventually smoking an hour before the senior design competition! We replaced it with a Fischer Price motor (thanks 2158!) and only turned on P. Every video after that shows only P (still pretty good I might say).

We won first place in the University of Texas EE Senior Design Competition!

There were many difficult parts to the project; designing a robotic arm from scratch in Solidworks, designing a PCB, etc. Jaguar made it possible to focus on other things because the position handling was pretty much taken care of for us. We used one RDK-BDC (Reference Design Kit) to get started talking to the Jags with CAN, but all the rest were regular MDL-BDCs like we got in the kit this year. Setting the ID was very simple: send out an ID set message from the control board, press the user button on the Jag that you want to set as that ID number, presto, the ID is updated.

I'll try and get some better pictures of the Jags and the CAN cables if people are interested.

Thanks for letting me show off my project :)

Let me know if you have questions,
David

Re: pic: cRIO CAN Jag
 

i just noticed in the picture that there is a split cord at the base of the cRio, one side goes to the jags and the other goes to an enclosure, is that another termination resistor?

Re: pic: cRIO CAN Jag
 

The CAN connectors are RJ11's, not RJ45's. RJ11's are the same as used in wired telephones. They have 4 pins. The above comments still apply however.

See: http://www.evalkits.com/files/BDC_Datasheet.pdf page 8

Re: pic: cRIO CAN Jag
 

Good eye. The NI catalog describes an accessory for the cRIO CAN module that is exactly that, a cable assembly which includes a termination resistor.

Re: pic: cRIO CAN Jag
 

It looks like it could be made easily, how much does NI sell it for? (We will probably get one in the kit though)

Also what module # is in the cRIO?
I know that the jags can do 1mb per second comms, and there is a 1mb module but there is the possibility of us having the slower comms, (Though i don't believe that we will ever need to have that much data throughput)

Re: pic: cRIO CAN Jag
 

Yes, but that shouldn't be surprising. The CAN bus uses 2 termination resistors, ideally located at each end. Both termination resistors are 120 ohm. Neither the Jaguar nor NI-9853 (*) provide internal termination since they make no assumptions regarding the bus topology nor where they are placed.

(*) This module was used by NI on NItro.. but I would not make any assumptions about this. NItro is a technology demonstration vehicle.

Re: pic: cRIO CAN Jag
 

The cable pictured is not available from NI. It was a small custom build for NItro. It is a small piece of 9 conductor ribbon cable with 4 flat ribbon DB-9 connectors crimped on it. One DB-9 is used for connecting to the Jaguars, one for connecting a termination resistor, one to connect to the NI CAN module, and the final for connecting a CAN bus analyzer. The parts are cheap and no soldering required.

A comment on the bus bandwidth.. the number of packets per second you can get on CAN depends on a number of factors. If you consider a 29-bit message identifier (as used by Jaguar) and average bit stuffing, on a 1 Mb/s network, you can get >12,800 1-byte packets per second and >9,300 4-byte packets per second. I bet that some crazy team will be complaining in a year or so about the need for more CAN bandwidth :). The nice thing about CAN is that there are no collisions, so you know when it is busy the data still gets through.

Re: pic: cRIO CAN Jag
 

I just wish that first would tell us that we can use the CAN bus in 2010 :rolleyes:

Re: pic: cRIO CAN Jag
 

Though at atlanta, the luminary micro and java people said that the Fpga image was gettting too large and they (WPI) would have to take some functionality out to get CAN in