Also, tooth count on one does not always equal tooth count on another, as it can be interpreted at 1x, 2x or 4x depending on the hardware. DOH appears to be using 2x, while Arkanoid uses 1x.
Sorry, you're losing me on this "hardware" thing... they both have identical hardware (a 2 led spinner) connected to the L and R of a jamma harness. To me, this means that there are the same number of pulses being sent to the PCB per revolution. As Doh does not jump more than one pixel at a time, I would argue that DOH uses 1x and Arkanoid uses 1/2x on the software side... 2x seems, to me, to indicate that DOH skips, which it doesn't.
A quadrature based optical device (spinner, mouse, trackball) can deliver up to 4x the number of apertures (teeth) in actual movement data. This is real data, not interpolated. But to get 4x, the hardware needs to be very fast, as the computations are more complex than the ones to get 2x the movement data, with 1x being the simplest.
Someone please correct me if I'm wrong, because this will skew the conclusions immensely, but from what I have heard discussed, the Arkanoid spinner has no logic on board and is just sending pulse data as any other spinner would. That means that there has to be a piece of hardware (with appropriate firmware) somewhere further up the chain that converts these pulses to movement data. The pulse waveforms are the same in both instances, but how they are interpreted is apparently different between the two machines. Because DOH has a smaller range of movement over the same travel of the Vaus, it indicates that more movement data is present and being acted upon than in Arkanoid.
Some of this research on Arkanoid was done by 2600 and u_rebel, and at the end of the day it was decided that Arkanoid used a 1x decoding based on the code of the ROM. When all of the numbers are crunched, (number of apertures, screen res, number of Vaus positions, ect) this adds up to 132 degree knob turn to 1 screen traverse. If DOH has a 66 degree turn to screen traverse, which is in line with your observation on the real hardware, then it stands to reason that the code in DOH is acting on twice the amount of movement data as Arkanoid, given that all other factors are equal.
What does this mean for us? If we know that Arkanoid needs a modern (4x decoding) spinner with at least 122 apertures, then we can assume that DOH requires one with 244 apertures minimum for absolute authentic gameplay. Christian was correct in stating that the
first version of the TurboTwist is below this number. That means that in order to play DOH at the 66 degree knob turn to screen traverse relationship, the MAME sensitivity level would need to be increased to 187%, which is fortunately within MAME's sensitivity scale, but increases the granularity of movement (skips every other on-screen position). In all fairness, it should also be mentioned that other spinner controls with apertures in the 48 to 50 range would require a sensitivity setting in the 500% area, which is twice what MAME allows, but even if it were possible, would cause the Vaus to jump 5 positions at a time.
The other option with either variety of spinner is to not introduce granularity issues, rather change the amount of movement required at the knob. WIth DOH, using a spinner with a 130 aperture encoder wheel at 100% (no position skipping) would change the knob range to 124 degrees, which is a little smaller than that of Arkanoid, which makes it playable, but not authentic. However a spinner with 50 apertures would require a range of 320 degrees (again, with no position skipping) which is almost one complete revolution to get the Vaus from one side of the screen to the other. As one would expect, there is a larger issue there.
The best approach to handle this situation, outside of buying a new spinner, would probably be to find an area in-between larger granularity and movement range that you feel you can live with.
Is the hardware truly identical or could the gearing be different?
Consider that the # of apertures passing by is what makes a difference (and sample rate of course)? For example, you could have a large wheel that spins at one rate, or have a very small wheel with less holes in it, geared such that it spins very fast and the result is the same # of apertures passing over the sensor...
Another possible variable, but my hunch is that they are the same. Re-tooling costs money and DOH is faster paced, so the original control is probably the same, just being decoded at 2x.
I am confused about what you are confused about....It seems that you figured everything out in that Doh uses 2x and Arkanoid uses 1x....And davieboynj has basically confirmed it by testing his boards.
I've been following the thread, but I'm not sure what else are you looking for?
I'm not confused or looking for anything else. I've been at that conclusion for a while. However, I think there might only be a handful of people reading this that even know what 1x and 2x mean in this context. It's my intention to bring other readers along for the ride so they understand what all this is about, and why it can be important. Without all of the numbers, there's no way to think about it. Putting the numbers together is what took the time (and I'm trying to be as accurate as I can
)
Sorry if I went back over what 2600 and U_rebel wrote. This has been in the editor for a while and I'm not going back and changing it
Also, I modified a couple of numbers after going back through my notes. This should be pretty accurate, but if someone finds otherwise, please feel free to jump in.
Thanks,
RandyT
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Topic: Spinner resolution and Revenge of DOH (Read 18250 times)
