roboRIO Command Based Problems

[Ben Wolsieffer]

Originally Posted by King Nerd III

We do occasionally and randomly get an error that says something about MotorSafetyHelper.h not updating fast enough on line 117, but there are two problems. One is that MotorSafetyHelper.h has no line 117, and we start running it. Any ideas?

You are getting the MotorSafetyHelper error because you are not updating the motor outputs fast enough so the watchdog timer is expiring. If any execute method blocks for a long time, it will prevent all commands from running, therefore causing a watchdog timeout.

[King Nerd III]

Originally Posted by lopsided98

You are getting the MotorSafetyHelper error because you are not updating the motor outputs fast enough so the watchdog timer is expiring. If any execute method blocks for a long time, it will prevent all commands from running, therefore causing a watchdog timeout.

That's what we thought, but it doesn't happen every single time, which confused me. How would we fix that?

[Alan Anderson]

Originally Posted by King Nerd III

How would we fix that?

That depends on what is making it take too long. We can guess at possible causes, but unless you show us your code we can't give confident help.

Post your code, as Kyle suggested in his first response.

[King Nerd III]

Originally Posted by Alan Anderson

That depends on what is making it take too long. We can guess at possible causes, but unless you show us your code we can't give confident help.

Post your code, as Kyle suggested in his first response.

I added the DriveBase subsystem, and the drive command to the post. Tell me what you think.

[kylelanman]

 48void DriveBase::AutoDriveTurn(float speed, float angle){
 49         while(drive_gyro->GetAngle() >= angle){
 50                 fl_motor->Set(speed);
 51                 fr_motor->Set(speed);
 52                 bl_motor->Set(speed);
 53                 br_motor->Set(speed);
 54         }
 55 }

This function is going to cause you problems. This is called a "tight loop" and will consume all of your CPU power while blocking your main thread. Because there is no delay the CPU is going to execute the loop as fast as it possibly can. It will likely take the CPU to 100% and then start dropping control packets from the driver station. On top of that while you are in the loop none of your other commands or code in the main thread will be running.

The better way to do this that won't cause you problems is to use a command.

 32 class AutoDriveTurnCommand() {
 33 private:
 34     double mSpeed;
 35     double mAngle;
 36 public:
 37     AutoDriveTurnCommand(double speed, double angle) {
 38         mSpeed = speed;
 39         mAngle = angle;
 40     }
 41     void Initialize() {
 42         Robot::drivebase->DriveTank(speed, speed);
 43     }
 44     void Execute() {}
 45     bool IsFinished() {
 46         return Robot::drivebase->GetGyroAngle() < mAngle;
 47     }
 48     void End() {
 49         Robot::drivebase->DriveTank(0, 0);
 50     }
 51     void Interrupted() {
 52         End();
 53     }
 54 };

For this to work you will need to define a function in DriveBase called GetGyroAngle that returns the angle of the gyro.

[King Nerd III]

Originally Posted by kylelanman

 48void DriveBase::AutoDriveTurn(float speed, float angle){
 49         while(drive_gyro->GetAngle() >= angle){
 50                 fl_motor->Set(speed);
 51                 fr_motor->Set(speed);
 52                 bl_motor->Set(speed);
 53                 br_motor->Set(speed);
 54         }
 55 }

This function is going to cause you problems. This is called a "tight loop" and will consume all of your CPU power while blocking your main thread. Because there is no delay the CPU is going to execute the loop as fast as it possibly can. It will likely take the CPU to 100% and then start dropping control packets from the driver station. On top of that while you are in the loop none of your other commands or code in the main thread will be running.

The better way to do this that won't cause you problems is to use a command.

 32 class AutoDriveTurnCommand() {
 33 private:
 34     double mSpeed;
 35     double mAngle;
 36 public:
 37     AutoDriveTurnCommand(double speed, double angle) {
 38         mSpeed = speed;
 39         mAngle = angle;
 40     }
 41     void Initialize() {
 42         Robot::drivebase->DriveTank(speed, speed);
 43     }
 44     void Execute() {}
 45     bool IsFinished() {
 46         return Robot::drivebase->GetGyroAngle() < mAngle;
 47     }
 48     void End() {
 49         Robot::drivebase->DriveTank(0, 0);
 50     }
 51     void Interrupted() {
 52         End();
 53     }
 54 };

For this to work you will need to define a function in DriveBase called GetGyroAngle that returns the angle of the gyro.

Thanks for the tip, but that couldn't be what's causing the error with not updating fast enough. That method isn't even called in the code yet, plus ita autonomous and we only get the error in teleop. Thanks for the tip, though! I'll probably use that!

[King Nerd III]

I know this is an old thread, and I'm replying to myself, but yesterday we figured out the problem. In the Robot.cpp we were calling auto_command->End(); in the TeleOpInit Phase, but we had not given a specific command to auto_command, so when TeleOp was enabled it couldn't end the command and just died... At least that's how I believe we fixed it. Commenting out the auto_command->End() got rid of this problem, so we believe that's what it was.
Hope this helps!
Isaac