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Atari trackball clean up & trackball mode?


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Trackball mode will send the pulses from the two encoder wheels plus direction signals to the four direction inputs of the controller. The horizontal pulses go to left and direction signal to right. The vertical pulses go to down and direction to up. The game has to count the pulses and calculate rotation speed and use the direction signals to determine which direction the ball is rolling. The only game I know of that came with support for that mode was the 400/800 version of Missile Command. Press Ctrl-T for trackball mode. Some games have been hacked to support it like Centipede for both the 400/800 and 7800.

 

 

edit: I mixed up the modes. corrected explanation.

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The advantage is in how the game handles the input. The joystick mode works by pulsing the different directions at a rate that's proportional to the ball speed. Like you were momentarily pushing the joystick. This is going to make the movement jerky at low speeds and might not have fine speed control depending on how the software reads the joystick.

 

In trackball mode, I'm guessing they changed to a speed/direction signal just to simplify reading the trackball. The main difference is that the game is expecting a trackball controller and is written to read these signals and calculate an accurate speed which can then be used to accurately control motion of the on screen object.

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Trackball mode will send the pulses from the two encoder wheels plus direction signals to the four direction inputs of the controller. The horizontal pulses go to left and direction signal to right. The vertical pulses go to down and direction to up. The game has to count the pulses and calculate rotation speed and use the direction signals to determine which direction the ball is rolling. The only game I know of that came with support for that mode was the 400/800 version of Missile Command. Press Ctrl-T for trackball mode. Some games have been hacked to support it like Centipede for both the 400/800 and 7800.

 

 

edit: I mixed up the modes. corrected explanation.

 

 

SLIME does too, surprisingly.

 

I still can't figure out why Atari didn't hammer the shit out of programmers to get them to use the TB. It's a great controller and vastly under-utilized by the 8-bits.

 

Of note, a couple of super-talented 2600 coders have rewritten 2600 titles to use true Trak-Ball mode in some classics: Missile Command (available on cart from the AA Store), Centipede, Millipede, Reactor, SW:The Arcade Game and one or two others. You might hit up the 2600 Forum for more info.

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Not quite. Atari made at least four different 2600/7800/A8-compatible Trak-Ball variants, in two different models, the CX-22 and CX-80. Early CX-22's have an external TB/Joystick mode switch, later versions do not (but the switch can be added). The first versions of the CX-80 output the same pulse train as the CX-22, but later versions were made ST Mouse-compatible for use with ST computers, evidently.

 

This is all discussed extensively in the 2600 forum thread I mentioned above, complete with 2600 code to determine which version is connected. That's actually rather important for CX-80 owners, who can't easily tell which version they might own.

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See my write up on the trackball that I restored. I explain the four types of trackballs.

https://fieldmouseprojects.wordpress.com/2016/06/30/part-1making-an-interface-for-atari-trackball-to-ti-994a/

Come to think about it, I don't know if I have the ST compatible or not. I probably need to check out that 2600 post.

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