Document enable/disable functionality for PIDController widget

[sciencewhiz]

The PIDController widget for SmartDashboard/Shuffleboard has an enabled boolean property that isn't supported by the new PIDController class. While it was very important to be able to disable the old PIDController since it automatically wrote to the motor, it is still helpful to pass the enabled flag to user code for while tuning with LiveWindow.

[cttdev]

With the new PIDController, the user is left with calling the calculate() method in their robot loop. I think it should be left to the user to implement an enable/disable toggle for the controller(perhaps using a SmartDashboard boolean) as they are the ones calling it, transitively they are the ones declaring when the output will be written too. This would also allow for the user to customize what the happens to the output when the controller is enable/disabled.

[Starlight220]

If this is settled, this issue should be closed.

[calcmogul]

We could add an example of the SmartDashboard boolean thing to frc-docs.

It's worth noting motors automatically disable in disabledPeriodic(). Users could just disable when changing the PID constants then reenable. Integrators would still run if the controller is in robotPeriodic(), but that was an issue with the old PIDController too.

[Daltz333]

Transferring to frc-docs. Should document how users can implement this.

[jasondaming]

I am confused as to what documentation is needed here. Is it why the boolean went away or how it can be added back? or what?

[Daltz333]

The new PIDController is ran via the calculate() method. We should provide an example of how to replicate the old functionality (enabling/disabling via dashboard) with the new PIDController. This can be done via a simple boolean toggle on the dashboard.

There are options that we have discussed and decided against:

• Duplicate PIDController Widgets (One for New PIDController and One for Old PIDController)
  • We aren't necessarily against this, but it really requires someone to open a PR in Shuffleboard, Smartdashboard, and WPILib providing a way to expose whether its a new PIDController or old PIDController, so it's non-trivial.
• Bring back the "enable" boolean, we decided against this as it violates the design of the new pidcontroller as being periodic and continuous.

I don't completely remember on the decision making for this as it was in one of our meetings several months back, so @calcmogul may be able to weigh in a bit more.

This issue is open to document replicating the enable/disable functionality via a NT boolean toggle box.