[C++] Use CAN Talons in RobotDrive

[1452-Leo]

We are using CAN for the first time and after a few hours of learning how to do it, wiring, and formatting the Talons, our drive code didn't work. I tried controlling each motor individually and it works perfectly, but we would like to use RobotDrive because we are using Mecanum wheels with a gyro. Here is the non-working code:

class Robot: public SampleRobot {
	Joystick driveStick;
	CANTalon leftFront;
	CANTalon leftBack;
	CANTalon rightFront;
	CANTalon rightBack;
	RobotDrive drive;
	Gyro gyro;
public:
	Robot() :
		driveStick(1),
		leftFront(1),
		leftBack(5),
		rightFront(2),
		rightBack(6),
		drive(leftFront, leftBack, rightFront, rightBack),
		gyro(0)
{}
	void OperatorControl() {
		gyro.InitGyro();
		gyro.Reset();
		while (IsOperatorControl() && IsEnabled()) {
			drive.MecanumDrive_Cartesian(driveStick.GetX(),driveStick.GetY(),driveStick.GetThrottle(),gyro.GetAngle());
		}
	}
};

And here is the working code (I used tank drive to make it easier):

class Robot: public SampleRobot {
	Joystick driveStick;
	CANTalon leftFront;
	CANTalon leftBack;
	CANTalon rightFront;
	CANTalon rightBack;
	Gyro gyro;
public:
	Robot() :
		driveStick(1),
		leftFront(1),
		leftBack(5),
		rightFront(2),
		rightBack(6),
		gyro(0)
{}
	void OperatorControl() {
		gyro.InitGyro();
		gyro.Reset();
		while (IsOperatorControl() && IsEnabled()) {
			leftFront.Set(-driveStick.GetY());
			leftBack.Set(-driveStick.GetY());
			rightFront.Set(driveStick.GetThrottle());
			rightBack.Set(driveStick.GetThrottle());
		}
	}
};

Does anyone know why this doesn't work? Thanks!

[viggy96]

Have you tried connecting the TalonSRXs via the PWM? That may alleviate your problem. Could also check if your TalonSRXs have the latest firmware.

Check here: http://crosstheroadelectronics.com/T...7s%20Guide.pdf

[ozrien]

Maybe grab the self test from the Rio web based configuration? Maybe its not in percent throttle mode. I don't have the implementation of robot drive in front of me but I think it just uses Set().

[James Kuszmaul]

What sort of problems are you encountering when you try to run the mecanum drive code? Does it simply not do anything at all, does it move the motors around but not in the way you expect, or something else? If the motors are running but the robot is responding how you expect, you should double check that everything is plugged into the right ports, that all the motors are turning the right direction, etc.

[1452-Leo]

Originally Posted by viggy96

Have you tried connecting the TalonSRXs via the PWM? That may alleviate your problem. Could also check if your TalonSRXs have the latest firmware.

Check here: http://crosstheroadelectronics.com/T...7s%20Guide.pdf

I updated all the Talons to 1.4 (the newest I think) and we're trying to use CAN instead of PWM. Using PWM would involve soldering the CAN wires which we don't want to do just yet.

Originally Posted by ozrien

Maybe grab the self test from the Rio web based configuration? Maybe its not in percent throttle mode. I don't have the implementation of robot drive in front of me but I think it just uses Set().

I actually did do this earlier, but I had no idea what is means. When in drive, they are set to "No Drive" but otherwise set to "Throttle." This seems like it could be the problem if I knew more about it.

Originally Posted by James Kuszmaul

What sort of problems are you encountering when you try to run the mecanum drive code? Does it simply not do anything at all, does it move the motors around but not in the way you expect, or something else? If the motors are running but the robot is responding how you expect, you should double check that everything is plugged into the right ports, that all the motors are turning the right direction, etc.

Motors are not doing anything at all, but works fine when not using RobotDrive.

[James Kuszmaul]

try calling
robotDrive.SetSafetyEnabled(false);
before the while loop in OperatorControl.
Edit: actually, try calling that in the Robot() constructor. It's possible that the Talons are getting disabled before you start running the robot but that they aren't getting properly re-enabled.

[1452-Leo]

Originally Posted by James Kuszmaul

try calling
robotDrive.SetSafetyEnabled(false);
before the while loop in OperatorControl.

I actually tried that earlier when I had some motor controllers set up wrong, but I forgot to try it again! I'll check back tomorrow and report if it worked or not.

[ozrien]

If you are seeing kNoDrive then most likely set is not being called. See software reference manual for more details.

[1452-Leo]

Originally Posted by ozrien

If you are seeing kNoDrive then most likely set is not being called. See software reference manual for more details.

Can I just call Set() once at the beginning of teleop or is there something I have to change in RobotDrive? Unfortunately, I can't test until Monday.

[TimTheGreat]

Are you calling Wait(.01) in your code? That may cause the code to do nothing.

[viggy96]

Could also try creating a new project. Sometimes projects get messed up. On the surface, it may not seem like it matters, but it could be worth a try.

I reccomend you switch from using the SampleRobot project to using IterativeRobot and try the code again.

[viggy96]

This should work, but as I don't have a bot with TalonSRXs, I can't confirm this, but you could try it. I have used the IterativeRobot class.

class Robot: public IterativeRobot
{
private:
	LiveWindow *lw;

	CANTalon leftFront = new CANTalon(1);
	CANTalon leftBack = new CANTalon(5);
	CANTalon rightFront = new CANTalon(2);
	CANTalon rightBack = new CANTalon(6);

	RobotDrive drive = new RobotDrive(leftFront, leftBack, rightFront, rightBack);

	Joystick stick = new Joystick(1);

	Gyro gyro = new gyro(0);

	void RobotInit()
	{
		lw = LiveWindow::GetInstance();
	}

	void AutonomousInit()
	{

	}

	void AutonomousPeriodic()
	{

	}

	void TeleopInit()
	{

	}

	void TeleopPeriodic()
	{
		drive.MecanumDrive_Cartesian(stick.getX(), stick.getY(), stick.getThrottle(), gyro.getAngle());
	}

	void TestPeriodic()
	{
		lw->Run();
	}
};

[1452-Leo]

Originally Posted by viggy96

This should work, but as I don't have a bot with TalonSRXs, I can't confirm this, but you could try it. I have used the IterativeRobot class.

How would this be different than the code I started with? Iterative basically just adds a function to be called at the beginning, but doesn't really change what is actually going on in the program.

[1452-Leo]

Ok I got it working! It's kind of an unusual workaround, but it works fine for us. Basically, create 4 fake motor controllers on unused PWM ports, and pass those to RobotDrive. From there, set the values of the real motor controllers to the values of the fake ones. Here is part of the code we used:

CANTalon *leftFront = new CANTalon(1); //Real ones
CANTalon *leftBack = new CANTalon(5);
CANTalon *rightFront = new CANTalon(2);
CANTalon *rightBack = new CANTalon(6);

TalonSRX *PWMlf = new TalonSRX(0); //Fake ones
TalonSRX *PWMlb = new TalonSRX(1);
TalonSRX *PWMrf = new TalonSRX(2);	
TalonSRX *PWMrb = new TalonSRX(3);	

void TeleopPeriodic()
{
	drive->MecanumDrive_Cartesian(driveStick->GetX(), driveStick->GetY(), driveStick->GetZ(), gyro->GetAngle());
	leftFront->Set(PWMlf->Get());
	leftBack->Set(PWMlb->Get());
	rightFront->Set(PWMrf->Get());
	rightBack->Set(PWMrb->Get());
}

[ozrien]

The problem looks like it's motor safety tripping. I reproduced the symptom with a similar project. Either the robot hits the motor safety trip once it boots up, or it fires during disable-to-enable transitions. When this happens the driver station will throw the MotorSafetyHelper assert (Section 16.14 in Talon SRX software reference manual), and the self-test will report "No-drive ".

I bet if you just called m_robotDrive->SetLeftRightMotorOutputs(0,0) in the disabled loop, that will keep feeding the motor safety object often enough to prevent your problem.

Or alternatively just TURN OFF the feature with...
m_robotDrive->SetSafetyEnabled(false)

Using dummy PWM objects seems like a drastic workaround.

Here's what I tested. If you comment out DisabledPeriodic(), you can reproduce the problem.

#include "WPILib.h"
class MecanumDefaultCode : public IterativeRobot
{
	CANTalon lf; /*left front */
	CANTalon lr;/*left rear */
	CANTalon rf; /*right front */
	CANTalon rr; /*right rear */
public:
	RobotDrive *m_robotDrive;		// RobotDrive object using PWM 1-4 for drive motors
	Joystick *m_driveStick;			// Joystick object on USB port 1 (mecanum drive)public:
	Gyro gyro;
	/**
	 * Constructor for this "MecanumDefaultCode" Class.
	 */
	MecanumDefaultCode(void) : lf(3), lr(1), rf(4), rr(5),  gyro(0)
	{
		// Create a RobotDrive object using PWMS 1, 2, 3, and 4
		m_robotDrive = new RobotDrive(lf, lr, rf, rr);

		/* alternatively you can disable safety features if you are not source-level debugging.
		 * uncomment this line to disable safety features. */
		//m_robotDrive->SetSafetyEnabled(false);

		// Define joystick being used at USB port #0 on the Drivers Station
		m_driveStick = new Joystick(0);
	}
	void TeleopInit()
	{
		gyro.Reset();
	}
	/** @return 10% deadband */
	double Db(double axisVal)
	{
		if(axisVal < -0.10)
			return axisVal;
		if(axisVal > +0.10)
			return axisVal;
		return 0;
	}

	void DisabledPeriodic(void)
	{
		/* while we are disabled, keep calling robotDrive's
		 * set routine to keep feeding the safety helper */
		m_robotDrive->SetLeftRightMotorOutputs(0,0);
	}
	/**
	 * Gets called once for each new packet from the DS.
	 */
	void TeleopPeriodic(void)
	{
		/* grab angle */
		float angle = gyro.GetAngle();

		/* printf for debugging - leave commented so it does affect performance. */
		//std::cout << "Angle : " << angle << std::endl;

		/* use angle with mec drive */
		m_robotDrive->MecanumDrive_Cartesian(	Db(m_driveStick->GetX()),
												Db(m_driveStick->GetY()),
												Db(m_driveStick->GetZ()),
												angle);

		/* my right side motors need to drive negative to move robot forward */
		m_robotDrive->SetInvertedMotor(RobotDrive::kFrontRightMotor,true);
		m_robotDrive->SetInvertedMotor(RobotDrive::kRearRightMotor,true);
	}
};
START_ROBOT_CLASS(MecanumDefaultCode);