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720 "Spinner Joystick"- I'll let you know

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PL1:

--- Quote from: J_K_M_A_N on February 01, 2023, 05:27:14 pm ---So, in theory, if the position disc was missing teeth, would the guy on the screen jump to the up position when the calibration disc hit its position? I am just wondering how it would actually calibrate if the position disc is off for whatever reason.

--- End quote ---
Yes, the skater will align to "up" when the calibration signal is triggered.
- IIRC, you can confirm this in MAME v0.142 or newer versions where the "Machine Configuration" menu option of controller type includes "real".  Not sure what other settings to adjust to get the snap alignment, but there was a related thread about it here.

The position disc works just like a spinner.
- It outputs relative position changes. i.e. two steps clockwise, 5 steps counter-clockwise
- When the game board boots up, it doesn't know what direction the joystick is pointing until the calibration disc triggers.

The calibration disc is mounted so the tooth is aligned with the calibration optos when the handle is in the 12 o'clock position.
- This provides an absolute position.  i.e. When the calibration optos trigger, the joystick is passing through the 12 o'clock position.  Now that it knows where "up" is, any changes from the position wheel are relative to that "up".


--- Quote from: J_K_M_A_N on February 01, 2023, 05:27:14 pm ---Or does it only calibrate on a specific screen?

--- End quote ---
It calibrates throughout gameplay.

Every time the joystick handle passes through the 12 o'clock position, the slots on the calibration disc pass through the calibration optos, triggering a calibration signal that tells the game PCB to turn the skater to face 12 o'clock.


--- Quote from: J_K_M_A_N on February 01, 2023, 05:27:14 pm ---I would think, once it knows which way it up, it would not need to calibrate again as it would be programmed for that encoder wheel.

--- End quote ---
Remember that the encoder wheel outputs relative position changes, not an absolute position.
- If the spinner alone could hold calibration, there would be no need for the calibration disc.

I suspect that part of the problem also has to do with how the game logic applies the directional angle and speed (a vector) to the grid-like layout of the playfield.
- Add in the possibility of jitter or backlash on the position encoder wheel and it makes sense that Atari would add the calibration disc.


Scott

J_K_M_A_N:
So, if it calibrates every time, what would happen if your position disc was messed up. Like if it was missing teeth or you replaced it with one with a different TPI. A 90% turn could register as a 50% turn and when you hit 100%, it would snap to straight up.

I guess what I am thinking is, the position disc itself must be somewhat close. Otherwise, if you don't hit straight up, it could keep getting off more and more (thinking about the downhill part...it has been a long time since I played).

Obviously, in real game play, you are going to hit straight up quite a bit doing all the spins. I am thinking more in technical terms. Completely pointless other than my own curiosity of how things work. Feel free to ignore me.  :dunno

PL1:

--- Quote from: J_K_M_A_N on February 01, 2023, 11:47:35 pm ---So, if it calibrates every time, what would happen if your position disc was messed up. Like if it was missing teeth or you replaced it with one with a different TPI. A 90% turn could register as a 50% turn and when you hit 100%, it would snap to straight up.

--- End quote ---
If the encoder wheel is damaged/broken, repair it using the correct part.   ::)

Wrong size teeth will cause the optos to not work.




--- Quote from: J_K_M_A_N on February 01, 2023, 11:47:35 pm ---I guess what I am thinking is, the position disc itself must be somewhat close.

--- End quote ---
It is very close, but isn't perfect so the calibration disc gives a little nudge when needed.

The only time you're likely to see a large calibration adjustment is on the very first time after booting the system.


Scott

J_K_M_A_N:
I find that pretty interesting. Thanks for taking all that time to explain it.

J_K_M_A_N

KenToad:
It seems like no one has gotten active autocentering to work properly in 720 on MAME and it looks like the controls are mapped incorrectly by the MAMEDEVS, at least in MAME .237. You cannot map a non-analog control to be an autocenter button and, when you map buttons to autocenter inc or dec, that just makes your skater rotate towards the 12 o'clock position when you press those buttons, rather than snapping to that position like it seems like it should.

I don't know. Maybe it is correct and the skater just slowly corrected toward the 12 o'clock position whenever the autocentering notches were triggered. Are we really even certain that it is an active calibration? I watched the game get calibrated on John's Arcade Youtube channel and it seems like the calibration disc is just telling the system where 12 o'clock is during calibration. If there is active calibration during gameplay, it's not obvious.

There's nothing in the 720 arcade manual talking about active calibration. Does anyone have a definitive answer to this question, maybe a good explanation of how it works in game and how MAME is emulating that?

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