Problems with high-resolution mice on STs?

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iggydrougge
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Problems with high-resolution mice on STs?

Postby iggydrougge » Sun Apr 30, 2017 1:53 pm

I have a habit of converting optical mice for Amiga use. In case the mouse uses a suitably old controller (many PS/2 era optical mice), I just tap the quadrature signals directly from the mouse. If it uses an unsuitable controller, I use a PIC with PS2M firmware to make a small adapter. On the Amiga, both kinds work fine, but when I try to rewire it for the ST, the mouse pointer starts moving erratically upon rapid movements — otherwise, it works fine.

Is this due to the ST using too small a counter for mouse movements — causing overflow on big movements — or is there a suitable fix I've overlooked?

czietz
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Re: Problems with high-resolution mice on STs?

Postby czietz » Sun Apr 30, 2017 2:47 pm

I encountered this as well with my firmware for converting PS/2 mice to Atari. I decided to cap the maximum speed of the mouse in the firmware. I think the main reason is that on the ST the mouse input signals are multiplexed with the keyboard matrix. Hence, the state of the quadrature encoders is only polled every 2 ms. If the quadrature signals change faster than that, the keyboard processor can't determine the movement of the mouse anymore.

joska
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Re: Problems with high-resolution mice on STs?

Postby joska » Sun Apr 30, 2017 2:50 pm

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iggydrougge
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Re: Problems with high-resolution mice on STs?

Postby iggydrougge » Mon May 01, 2017 12:58 am

Do you remember what value you put the cap at, czietz?

czietz
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Re: Problems with high-resolution mice on STs?

Postby czietz » Mon May 01, 2017 8:04 am

I didn't remember -- long time ago. But I looked it up in my firmware -- and I hope I got it right. As you surely know, there are four states of the quadrature signal. My firmware goes from one state to another at a maximum frequency of slightly less than 1 kHz, i.e. the individual signal lines themselves change less than 500 times per second. BTW: I remember, however, that finding a mapping of PS/2 mouse movements to Atari mouse movements that felt right was the most complicated task in programming the firmware.


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