Analog joystick resolution

[8bitAndy]

What is the maximum resolution you can read from one of the 5200 joystick axis?

[Rybags]

The resolution is limited by the hardware that reads the pots.  Pokey gives values 0-227.

Example of another computer is C64 where it gives the full 0-255 range.  But the paddles on the 2 machines aren't 100% compatible since C64 uses 500K pots and Atari uses 1M.

So Atari paddles on C64 will only use a fraction of the turning range and C64 paddles on Atari will only return a subset of the possible values.

[8bitAndy]

3 hours ago, Rybags said:

The resolution is limited by the hardware that reads the pots.  Pokey gives values 0-227.

Thanks for this info. I'm experimenting with a new controller for the 5200. Is there any guidance or conventions on a deadzone to use when using the joystick as a digital controller?

 

For example, if 0-113 are on the left side of the axis, and 114-227 are on the right side, is 113 considered "left" in a game like PacMan, or do games usually consider values around 113 to be null, and left isn't triggered until the value is 90 (for example) or below?

 

Or is this something each developer decides on their own?

[Rybags]

I've not had much to do with the 5200 other than using it via emulation.

Likely you'd want a dead zone in the middle and possibly also assume that some of the extreme values aren't available.

 

The dead zone I should think would probably cover at least 20 values.

[TGB1718]

7 hours ago, 8bitAndy said:

Or is this something each developer decides on their own?

This is down to the developer, I've seen some games where the "dead zone" is far too small and when hands off

there is movement on screen, depending what your doing I think the best bet is try different values and see how it

goes, remembering all joysticks are not equal so allow a small % for these differences

[drpeter]

Another critical consideration is how easy (or hard) you want to make it to trigger diagonal readouts if you are translating an analog joystick to an 8-way readout.

 

This can depend a lot on the mechanics of the game controls.  You don't want to tend to trigger diagonals when the player was intending an orthogonal and vice versa.

 

The original Atari 8-way joysticks were easier to trigger in orthogonal directions than diagonal and it was a particular skill to move directly from neutral to a diagonal position, which was required with precision in some platform games.

[Rybags]

The usual with digital at least is left/right is preferred and up/down occurs accidentally.

Implementation would be easy enough - just do the l/r processing first and if there is movement, increase the required threshold to detect u/d.

 

Of course it'd be nice to have user options for deadzones, thresholds etc but I can't recall any 5200 games that allow such things.

[Kr0tki]

On 11/30/2020 at 4:07 AM, 8bitAndy said:

 Or is this something each developer decides on their own?

Read the "PAM Package" technical document - it's a developer's guide used internally at Atari. It describes the techniques they were using.

[8bitAndy]

3 hours ago, Kr0tki said:

Read the "PAM Package" technical document - it's a developer's guide used internally at Atari. It describes the techniques they were using.

Great document, thanks for linking it.