Chief Delphi - CANJaguar

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Java (http://www.chiefdelphi.com/forums/forumdisplay.php?f=184)

- - CANJaguar (http://www.chiefdelphi.com/forums/showthread.php?t=100713)

kingkurry

20-01-2012 21:06

Re: CANJaguar

Yes I tried that as well. I declared 4 of them. Something along the lines of

SpeedController frontLeft = new Jaguar(1,1);
SpeedController rearLeft = new Jaguar(1,2);
SpeedController frontRight = new Jaguar(1,3);
SpeedController rearRight = new Jaguar(1,4);

To be honest, I am not entirely sure what the slot number on the chassis is supposed to signify, so i just used 1 because that seems to be what everyone used in the examples i have seen. For the channel number, I used the PWM slot number i connected each jaguar to on the digital side car.

Then I used the set method, passing in the throttle value from a joystick, to set the speeds. Then I passed the speed controllers into the tankDrive() method.

One more thing that i have noticed is that the the green diagnostic light in the driver station diagnostic console doesnt change color to blue when i move the sticks. It does, however, change color when i press buttons on the stick. Does this have any significance?

nickpeq

20-01-2012 21:17

Re: CANJaguar

Quote:

Originally Posted by kingkurry (Post 1110112)

If the code isn't working, try removing the slot number. Instantiate your Jaguars with only the PWM number. Also, I've never used "SpeedController x = new Jaguar(etc)". I believe I always use "Jaguar x = new Jaguar(blah)"... If that makes any difference.
And the dashboard is just like that. No real significance. It changes color only for button-presses.

Kodiak

20-01-2012 21:22

Re: CANJaguar

Quote:

Originally Posted by nickpeq (Post 1110123)

I do what nick does, works just fine for me, and for Java I think the Digital Side car module is on the second slot and for Labview the 4th one, maybe you have one of the modules wrong?

CodeYeti

21-01-2012 00:31

Re: CANJaguar

We had some problems with things getting initiated at the beginning of the year because some standards have changed with regards to the numbering of the modules. Your digital module should be in slot 2, and then you should just remove the slot number from the lines that instantiate the motors. Also, how to OTHER things connected to the sidecar work? I saw a person earlier today that had a faulty ribbon cable.

Mike Copioli

21-01-2012 10:14

Re: CANJaguar

Quote:

Originally Posted by dyanoshak (Post 1109992)

Bryscus is correct:

We found that 20' of cable, 100 ohm termination resistors, and ~16 Jags on a bus is a good limit for reliable operation. It may be possible to get more Jags, but the cable lengths will have to be shorter.

-David

David,

I have to disagree with you on this. According to CAN spec IS0 11898:1993(E) Table 15, the maximum cable distance for 1Mbit/second is 40 Meters not 20 feet.

We have also tested at distances much greater than 20 feet without issue using 120 Ohm's of termination on each end of the BUS.

FYI a termination resistor of 100 ohms is outside of the spec. Teams using 120 ohms resistors should have no issues related to signal reflection.

Bryscus

21-01-2012 21:52

Re: CANJaguar

Quote:

Originally Posted by Mike Copioli (Post 1110392)

From the getting started guide:

Total Cable Length
(maximum)
20 ft / 6.1m Tip: Start with this length of bulk cable and cut all
segments from it to ensure compliance.

Termination Resistance 100 At each end of the network.

Just quoting specs.

- Bryce

Kodiak

22-01-2012 01:22

Re: CANJaguar

Quote:

Total Cable Length
(maximum)
20 ft / 6.1m Tip: Start with this length of bulk cable and cut all
segments from it to ensure compliance.

Termination Resistance 100 At each end of the network.

Just quoting specs.

Hmm, it may be that 20 feet is the best length for the best outcome, but if you need more it may not be THE limit.

otherguy

22-01-2012 13:15

Re: CANJaguar

Quote:

Originally Posted by kingkurry (Post 1110112)

To be honest, I am not entirely sure what the slot number on the chassis is supposed to signify, so i just used 1 because that seems to be what everyone used in the examples i have seen. For the channel number, I used the PWM slot number i connected each jaguar to on the digital side car.

For 2012 I believe the Java methods referring to "Slot" numbers essentially mean the instance of the particular card you are trying to access. I think the same is true for how LabVIEW is identifying the modules. For example: in the 8 or 4 slot cRIO chassis the DIO module in slot position two would be identified to the program as "Slot" 1. A second DIO module in slot position 4 (on the cRIO II) or slot position 6 (on the cRIO) would be identified to the program as "Slot" 2.

I think this deviates from what "Slot" meant in the past: the actual physical position the card was at (i.e. slot 4 of 8 for previous years was the slot for the first DIO module)

Again this is just what I remember from beta test, and what I've observed from my testing. If I'm wrong, let me know so I can avoid headaches down the road. :o

Mike Copioli

22-01-2012 14:54

Re: CANJaguar

Quote:

Originally Posted by Bryscus (Post 1110879)

The 'Getting Started Guide' is not the CAN spec, IS0 11898:1993(E) is.

kingkurry

22-01-2012 15:20

Re: CANJaguar

Quote:

Originally Posted by nickpeq (Post 1110123)

I just tried instantiating the jaguars without a slot number. This didn't work either. This is the code I have been trying. I have also tried all the code that I commented out, still without results

Code:

package edu.wpi.first.wpilibj.templates;





import edu.wpi.first.wpilibj.IterativeRobot;

import edu.wpi.first.wpilibj.Joystick;

import edu.wpi.first.wpilibj.RobotDrive;

import edu.wpi.first.wpilibj.Solenoid;

import edu.wpi.first.wpilibj.Timer;

import edu.wpi.first.wpilibj.Watchdog;

import edu.wpi.first.wpilibj.SpeedController;

import edu.wpi.first.wpilibj.Jaguar;



public class RobotTemplate extends IterativeRobot {

    RobotDrive robot;

    Joystick left;

    Joystick right; 

    Jaguar leftFront;

    Jaguar leftRear;

    Jaguar rightFront;

    Jaguar rightRear;

    

    public void robotInit() {

        Jaguar leftFront = new Jaguar(1);

        Jaguar leftRear= new Jaguar(2);

        Jaguar rightFront= new Jaguar(3);

        Jaguar rightRear= new Jaguar(4);

        

        robot = new RobotDrive(leftFront,leftRear,rightFront,rightRear);

  

        //robot = new RobotDrive(1,2,3,4);

        left = new Joystick(1);

        right = new Joystick(2);

        System.out.println("RobotInit() completed.\n");

    }

    

    public void disabledContinuous(){

        leftFront.set(1);

        //robot.tankDrive(1,1);

        

        

    }

    

    public void disabledPeriodic(){

        leftFront.set(1);

        //robot.tankDrive(1,1);

    }



    public void autonomousPeriodic() {

        leftFront.set(1);

        //robot.tankDrive(1,1);



    }

    

    public void teleopContinuous(){

        leftFront.set(1);

        //robot.tankDrive(1,1);

    }



    public void teleopPeriodic() {

        //robot.tankDrive(left.getThrottle(),(-1*right.getThrottle()));

        leftFront.set(1);

        //rightFront.set(right.getMagnitude());

        //robot.tankDrive(leftFront.get(), rightFront.get());

        

        //robot.tankDrive(left, right);

        //robot.tankDrive(1,1);

       

        

        //System.out.println("left:"+left.getThrottle());

        //System.out.println("right:"+right.getThrottle());

        //System.out.println("LMAG:"+ left.getMagnitude());

        //System.out.println("RMAG:"+ right.getMagnitude());

        //System.out.println("LRAD"+left.getDirectionDegrees());

        //System.out.println("RRAD"+right.getDirectionDegrees());

        

        System.out.println("Tank Drive");

    }

    

}

As you can see, I have tried to create a robot drive specifying the pwm outputs, then driving it with tankDrive(2,2)

I have also tried creating jaguar objects and setting their speed manually. Again this did not work.

I even took a multimeter to my sidecar, testing each of the signal pins in both the 3 pin PWM and the 3 pin Digital I/O. No matter what code I tried, the signal pins never presented any current.

What do you guys think the problem could be? My code looks fine right? Could it be the ribbon cable connecting the cRIO to the sidecar?

Bryscus

22-01-2012 17:02

Quote:

Originally Posted by Mike Copioli (Post 1111252)

The 'Getting Started Guide' is not the CAN spec, IS0 11898:1993(E) is.

Mike,

This wouldn't be the first time a device isn't fully compliant with a spec. One thing I've learned in the industry is that if you design a system to the spec of a bus and not that of a part you'll get burned every time - SPI, I2C, EBI, you name it. The reason microprocessors have so many options for these buses is that parts are so varied.

- Bryce

dyanoshak

22-01-2012 17:37

Re: CANJaguar

Quote:

Originally Posted by Mike Copioli (Post 1110392)

Yes, that is what the CAN spec says. However, I am talking about what we specify for Jaguar.

They differ in the following ways:

CAN Spec states 40 meter cable lengths using twisted pair cable
- Jaguar uses non-twisted modular cable
CAN Spec states 120 ohm terminators
- TI specifies 100 ohm terminators for the following reasons:

The concern is with bit timing, not signal reflections.

Ideally each Jaguar would be configured with its own specific bit-timing parameters (parameters that define when the CAN module samples the bit). These parameters depend on a lot of factors including location on the bus, bus impedance, the number of drivers on the bus, etc.

In this specific application (FRC) a lot of those factors are unknown. What works for one setup may not work as well for another. During our testing of Jaguar we found that as the number of Jaguars increased and the cable lengths got longer, some Jaguars would not sample the bits correctly. We saw that the bus was taking longer to transition from the dominant to recessive states fast enough when every CAN driver on the bus was driving dominant.

We were able to successfully improve the timing by lowering the resistance of the terminator to 100 ohms. The lower resistance helped pull the CANH and CANL to the recessive state much faster. We also found that minimizing the cable lengths between the Jaguars helped a bit too.

The bottom line:

TI specifies 100 ohm termination resistors and ~20' total of cabling. This differs from the official ISO specification for CAN, but should ensure that teams have the best experience with the Jaguar when using CAN.

-David

Mike Copioli

22-01-2012 21:38

Re: CANJaguar

Quote:

Originally Posted by dyanoshak (Post 1111370)

Yes, that is what the CAN spec says. However, I am talking about what we specify for Jaguar.

They differ in the following ways:

CAN Spec states 40 meter cable lengths using twisted pair cable
- Jaguar uses non-twisted modular cable
CAN Spec states 120 ohm terminators
- TI specifies 100 ohm terminators for the following reasons:

Dave,

Our findings tell a different story. I would be happy to share them with you.

otherguy

23-01-2012 01:19

Re: CANJaguar

Quote:

Originally Posted by kingkurry (Post 1111276)

I just tried instantiating the jaguars without a slot number. This didn't work either. This is the code I have been trying. I have also tried all the code that I commented out, still without results

Code:

package edu.wpi.first.wpilibj.templates;





import edu.wpi.first.wpilibj.IterativeRobot;

import edu.wpi.first.wpilibj.Joystick;

import edu.wpi.first.wpilibj.RobotDrive;

import edu.wpi.first.wpilibj.Solenoid;

import edu.wpi.first.wpilibj.Timer;

import edu.wpi.first.wpilibj.Watchdog;

import edu.wpi.first.wpilibj.SpeedController;

import edu.wpi.first.wpilibj.Jaguar;



public class RobotTemplate extends IterativeRobot {

    RobotDrive robot;

    Joystick left;

    Joystick right; 

    Jaguar leftFront;

    Jaguar leftRear;

    Jaguar rightFront;

    Jaguar rightRear;

    

    public void robotInit() {

        Jaguar leftFront = new Jaguar(1);

        Jaguar leftRear= new Jaguar(2);

        Jaguar rightFront= new Jaguar(3);

        Jaguar rightRear= new Jaguar(4);

        

        robot = new RobotDrive(leftFront,leftRear,rightFront,rightRear);

  

        //robot = new RobotDrive(1,2,3,4);

        left = new Joystick(1);

        right = new Joystick(2);

        System.out.println("RobotInit() completed.\n");

    }

I believe you have a scope problem.
You instantiate your jaguars as class variables (green lines), then create four new jaguar variables within the robotInit() method (red lines). You're not initializing the class variables as you may think. Basically you're telling the program that within the robotInit() class it should use the local copies of those Jag variables (red), instead of the ones the rest of the program knows about (green). Any reference to the Jag variables outside of the robotInit() method will refer to the ones that aren't initialized (green), and since they aren't initialized they won't be sending commands to any motor controllers.

Remove the "Jaguar" text thats highlighted red and that should fix your problem.

Read up on scope: http://sip.clarku.edu/tutorials/java/java.html#scope

Kodiak

23-01-2012 02:11

Re: CANJaguar

Quote:

Originally Posted by otherguy (Post 1111672)

Yup, he is right, you having that is like pretty much trying to make two jaguars of the same variable name, and in any programming language you can't simply do that.

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