Active Brake

By default, the drivetrain is on coast where if you let go of the joysticks the robot will continue to move a bit.  Generally, this seems like the preferred way the community likes to control their robots, and people don't really like the feel of driving on brake or hold (which is a decision that's fully preference-based).  

Active brake gives you more control than these 3 states.  Active brake will run a P loop when you let go of the joysticks, giving you full control over how aggressive this is.  You can use it along with coast and have the kP be super low so you still feel like it's on coast but it'll only move so far.  

void initialize() {
  // . . .
  chassis.opcontrol_drive_activebrake_set(2.0);  // Sets the active brake kP. We recommend ~2.  0 will disable.  
  // . . .
}