joystick problems?

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joystick problems?

Postby samplefiend » Wed Jul 21, 2010 7:28 pm

Hiya everyone,

Forgive yet anothger query but I got my hands on some joysticks from ebay recently and have been trying them out with some games. The joysticks seem to work fine - control is nice and the fire buttons work great. One thing i've noticed though is that playing with joysticks instead of keys seems to create a lot of background noise in some games.

Devil Assault works without any noise for example. Danger Ranger & Katerpillar Attack make no noise when the stick is to the left but if you move it to the right the noise gets louder. Donkey King and Time Bandit make noise most of the time regardless ...

I've also got a dragon quickshot stick and the same thing happens with it too.

any ideas folks?

cheers again

craig xxx
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Re: joystick problems?

Postby munkeyboy » Sun Aug 01, 2010 3:59 pm

Hello Craig,

The Dragon uses PIA0 to control joystick and also audio source selection (as well as other things). There is a reference to this in Dragon User August '84 page 45 under the title "Busily buzzing".
I can only guess that some software makes use of the PIA in a different way to others?
My electronic knowledge is limited to say the least, I can't see how it could but does anyone know if this can be resolved with a hardware fix?

Regards, Gareth
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Re: joystick problems?

Postby jmk » Mon Aug 02, 2010 7:53 pm

That sounds vaguely familiar... When I was programming Glove I found that exact same problem with clicks getting louder as I moved the joystick down or right. It didn't happen under emulation (then, not sure about now) just on the real thing.

I think it's something to do with the joystick taking longer to read when pushing down or right because of the way analogue joysticks work.

I made sure I switched off the 6-bit output (bit 3 of $FF23 reset and I cleared the output ($FF20) just in case) whenever I wasn't outputting any sound and that seemed to fix it, so it's probably a software issue with particular games.
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Re: joystick problems?

Postby zephyr » Wed Sep 01, 2010 2:41 pm

This problem occurs when games use the BASIC ROM joystick routine. Unlike the CoCo's, the Dragon's joystick routine does not disable audio.
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Re: joystick problems?

Postby zephyr » Thu Sep 02, 2010 12:44 am

You can get round this problem quite easily if you have a Dragon 64, or Dragon 32 with a 64K memory upgrade. I have written a small program which copies the BASIC ROM to RAM, and applies a patch to the joystick routine so that it disables audio in the exact same way as the CoCo. This program will stop the clicking sound occurring on most games. Just load, and EXEC the attached 'JOYFIX' before loading your game from disk or cassette.

Regards,
Steve

EDIT: Attachment removed.
Last edited by zephyr on Fri Sep 10, 2010 10:58 am, edited 1 time in total.
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Re: joystick problems?

Postby zephyr » Mon Sep 06, 2010 2:45 pm

This improved version has the following changes:

(1) Main patch code moved to unused bytes at $9FF8.
(2) Hardware initialisation routine patched to help prevent games from switching the computer back to 32K mode.
(3) RAM test routine patched to prevent ROM in RAM being overwritten if a game were to cold restart the computer.
Attachments
joyfix2.zip
(2.96 KiB) Downloaded 62 times
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Re: joystick problems?

Postby zephyr » Mon Jan 10, 2011 12:02 am

samplefiend wrote:Devil Assault works without any noise for example. Danger Ranger & Katerpillar Attack make no noise when the stick is to the left but if you move it to the right the noise gets louder. Donkey King and Time Bandit make noise most of the time regardless ...

I fixed all of these games, except for Time Bandit (The bug wasn't present in my copy), and uploaded them to the Uploads section of the forum.

Regards,
Steve
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Re: joystick problems?

Postby samplefiend » Mon Jun 13, 2011 4:36 pm

hi again steve,

many thanks for the file and for fixing the fixed dragon games i'd mentioned. it's great to play with the volume loud and not get distracted by the joystick interference!

keep up the great work,

craig xxx
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Buzzing joystick dependent sound

Postby Rolo » Thu Oct 10, 2013 7:36 pm

I'm having the same old problem now, patching CoCo-images for the Dragon multi-cart:
Some of the CoCo-programs have that joystick-dependent noise, since Dragon Color Basic does not, like CoCo, switch off audio, when it reads the joysticks' axis. That's easy to see comparing the assembly listings of CoCo and Dragon. I made tests with a patched "Polaris.rom", where I divert the jumps and switch off audio myself (jsr $bac3), before I jsr [$a00a] into the regular routine and finally rts back into the program. This is better, but nothing like a clean sound. Is there better way :?:
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