What happens if you play Pengo or Mr Dos Castle and other such games with track-ball?

[Giles N]

Will it just not respond?

 

Or just be very difficult to use to control?

[+Ryan Witmer]

I can answer this from a technical perspective, since I had to learn how the trak-ball works for my current homebrew project.

 

The normal Atari joysticks are basically the same as a pair of paddles.  You read a position value from each axis.  That value in is the range of 0 to about 220 or so.  Games typically set boundaries on this range where it decides "that's far enough, you're pushing left now" and react to the values that way.

 

The trak-ball also reports these numbers when you read it, but in this case the number indicates how fast the ball is spinning in a given direction.  The "rest" value varies from trak-ball to trak-ball, and there's a way you can get the rest value from the controller.  When the controller is read, the farther the numbers are away from the rest value, the faster the ball is spinning.

 

The problem is that the values from the trak-ball don't wander very far from the rest value.  They will usually be in the zone that a joystick would consider "centered" and you'd have to spin the ball really fast to get the sort of numbers a joystick game is looking for.  Because of this, games need slightly different code for handling the two types of controllers.

 

So, to sum up:  For most joystick games, the trak-ball will do next to nothing because you can't spin it fast enough to register as joystick movement.  If your particular trak-ball's rest value is really high or really low, you might get some movement in one direction, but not much more.

[Giles N]

6 minutes ago, AverageSoftware said:

I can answer this from a technical perspective, since I had to learn how the trak-ball works for my current homebrew project.

 

The normal Atari joysticks are basically the same as a pair of paddles.  You read a position value from each axis.  That value in is the range of 0 to about 220 or so.  Games typically set boundaries on this range where it decides "that's far enough, you're pushing left now" and react to the values that way.

 

The trak-ball also reports these numbers when you read it, but in this case the number indicates how fast the ball is spinning in a given direction.  The "rest" value varies from trak-ball to trak-ball, and there's a way you can get the rest value from the controller.  When the controller is read, the farther the numbers are away from the rest value, the faster the ball is spinning.

 

The problem is that the values from the trak-ball don't wander very far from the rest value.  They will usually be in the zone that a joystick would consider "centered" and you'd have to spin the ball really fast to get the sort of numbers a joystick game is looking for.  Because of this, games need slightly different code for handling the two types of controllers.

 

So, to sum up:  For most joystick games, the trak-ball will do next to nothing because you can't spin it fast enough to register as joystick movement.  If your particular trak-ball's rest value is really high or really low, you might get some movement in one direction, but not much more.

Ah, I see, thanks!