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Ryan Witmer

Trakball research, request for assistance

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I'm trying to work out some details about the trakball controller, and I could use a little help.

 

Unlike some of the 5200 superfans here, I only have one 5200 console and one trakball. I've started working on a project that will feature trakball support (I'll just leave this here) and I'm trying to get a sense of the sort of controller values that the trakball sends.

 

My research on this hasn't turned up much, and what little I've found seems to be not quite correct. What I'd like, if anyone is able, is for some kind volunteers to run the Diagnostic Cart's POKEY adjustment test.

 

This test displays the values that are currently coming from each controller. I'm interested in what sort of numbers come from a trakball that isn't moving. I'm mostly curious about how consistent these values are across different controllers.

 

Thanks in advance to anyone who can help me out with this.

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My research on this hasn't turned up much, and what little I've found seems to be not quite correct. What I'd like, if anyone is able, is for some kind volunteers to run the Diagnostic Cart's POKEY adjustment test.

 

This test displays the values that are currently coming from each controller. I'm interested in what sort of numbers come from a trakball that isn't moving. I'm mostly curious about how consistent these values are across different controllers.

 

Thanks in advance to anyone who can help me out with this.

 

 

I had some time to check this out, the readings when the Trak-Ball is *still* are a constant value of 130 Horizontal and 130 Vertical. These values change rapidly as the ball is spun, though they return when the ball is at rest.

This is curious to me, as the Atari field service manual stipulates that when adjusting joystick controller potentiometers, the "center" values should be 112 on joy1 and no other values should exceed 124. Any thoughts on what accounts for this difference?

 

post-26843-0-77885800-1540501717.jpg

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Wow. That's kind of alarming. My trak-ball hovers around 114 when at rest. That's a huge variation.

 

Do you have any problems with drift on any of the trak-ball games? Those values just seem awfully high.

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Wow. That's kind of alarming. My trak-ball hovers around 114 when at rest. That's a huge variation.

 

Do you have any problems with drift on any of the trak-ball games? Those values just seem awfully high.

 

As long as the values don't change while the ball is stationary, there will be no drift.

 

ALSO: the 5200 Field Service Manual has a chapter dedicated to the CX-53. It has a pretty good (technical) explanation plus schematics. In addition, there is a FB Group called "Trak-Bombers" dedicated to the Atari Trak-Ball (*). Dan Kramer, inventor of the CX-52 and CX-22 Trak-Balls, is a member. You might try picking his brain some there.

 

(*) I founded the group but didn't pick the name, lol. My co-founder did.

Edited by DrVenkman
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As long as the values don't change while the ball is stationary, there will be no drift.

 

ALSO: the 5200 Field Service Manual has a chapter dedicated to the CX-53. It has a pretty good (technical) explanation plus schematics. In addition, there is a FB Group called "Trak-Bombers" dedicated to the Atari Trak-Ball (*). Dan Kramer, inventor of the CX-52 and CX-22 Trak-Balls, is a member. You might try picking his brain some there.

 

(*) I founded the group but didn't pick the name, lol. My co-founder did.

 

Pretty sure you or Dan picked that name....

 

https://www.facebook.com/groups/trakbombers/

 

 

Dan also worked on the controllers for the unreleased Atari 2700 RC Stella, the Atari 2800/Sears Video Arcade II, worked on the SECAM version of the 800XL, created the first glow light for the Gameboy, and was the first person to commercially fix Playstations. I'm probably missing a bunch. Oh, and also famously creating the CX22 and CX53 Trak-Balls. Had the 5200 continued, he would've finished up the 5200 Driving Controller and the Yoke Controller... :)

Edited by Lynxpro

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Dan told me that the Trak-Ball controller can be used as a DIGITAL input! That's all he told me.

 

So I'm doing some research as to how it can be done!

 

Test points 5-6-7 & 8 are for testing UP-DOWN-LEFT & RIGHT!

 

I want to try a couple ideas and see what works.

 

If I get it to work, I can easily mount a 9-pin jack on the back and be able to plug in any 2600 controller or wire it to be compatible with a Sega Genesis controller for using 2 fire buttons!

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Dan told me that the Trak-Ball controller can be used as a DIGITAL input! That's all he told me.

 

So I'm doing some research as to how it can be done!

 

Test points 5-6-7 & 8 are for testing UP-DOWN-LEFT & RIGHT!

 

I want to try a couple ideas and see what works.

 

If I get it to work, I can easily mount a 9-pin jack on the back and be able to plug in any 2600 controller or wire it to be compatible with a Sega Genesis controller for using 2 fire buttons!

 

He may be busy. Track down BigO on here. He knows a thing or two about the Trak-Balls...

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I've been studding the 2600 CX-22 Trak-Ball schematic trying to figure out the Joystick/Trak-Ball switch and see what that does but the schematic doesn't show it!

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I've been studding the 2600 CX-22 Trak-Ball schematic trying to figure out the Joystick/Trak-Ball switch and see what that does but the schematic doesn't show it!

 

Summon BigO. He's the other Trak-Ball expert with what he's been able to do with them, mod-wise...

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I had some time to check this out, the readings when the Trak-Ball is *still* are a constant value of 130 Horizontal and 130 Vertical. These values change rapidly as the ball is spun, though they return when the ball is at rest.

This is curious to me, as the Atari field service manual stipulates that when adjusting joystick controller potentiometers, the "center" values should be 112 on joy1 and no other values should exceed 124. Any thoughts on what accounts for this difference?

 

IMG_6823.jpg

Im thinking this may be due to the potentiometer under the console cover. If Im remembering correctly it should be turned a little counter-clockwise

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Wow. That's kind of alarming. My trak-ball hovers around 114 when at rest. That's a huge variation.

 

Do you have any problems with drift on any of the trak-ball games? Those values just seem awfully high.

 

 

 

I had calibrated the console I used, the POKEY adjustment was dialed in at a perfect 112 Horizontal and Vertical readings for joysticks. The Trak-Ball doesn't show any problems with drift whatsoever, interestingly enough. When playing Missile Command, the reticule is dead center of screen at the start of every wave, I have full range of the screen north south east west without any erratic jumping or dead spots. Movement is fluid and accurate.

As the Trak-Ball is a digital device, perhaps it's unaffected by the analog centering circuitry? Interested to hear what others have to say on this too.

I have a few other Trak-balls, I will plug those in too and see if the readings are any different. Will hit up Dan Kramer as well :0)

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As long as the values don't change while the ball is stationary, there will be no drift.

 

Is the Trak-Ball simply ignoring the centering circuitry? Mine doesn't have any apparent calibration problems in game play, despite the horizontal and vertical readings being off in the Pokey test.

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I tried to see if the trak-ball games self-calibrate by caching a "rest" value to compare against, and so far I can't figure out what it's actually doing. I've tried starting various trak-ball games while spinning the ball like mad during every point that I believe it might check for a center value, and I can't seem to throw it off.

 

I suppose what might be happening is that the center value can be read when the controllers are disabled. The way you detect the type of controller is by disabling the controller ports are trying to read a value. Joysticks give a very specific value when you do this, while the trak-ball does... something else.

 

It's still a mystery to me.

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Allan posted Dan Kramer's 5200 trak-ball guide here if you have not already seen it:

 

http://atariage.com/forums/topic/125406-8-bit-conversions/?p=3306094

 

Oooh, that's nice. Thanks a lot.

 

Between this thread, some of this documentation, my own experiments, and some time thinking in the shower, I think I might have this whole thing figured out.

 

I plan to rewrite the trak-ball code in my current project to test out some of this stuff. I'll post a demo ROM here at some point and it would be great if some folks could test it out to make sure my understanding isn't totally broken.

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Alright, that was quicker than expected.

 

Attached is a very early build of my latest project. It's configured for two players, and should recognize a trak-ball for either/both players. Here's a screenshot so you know what you're dealing with:

 

Magical Fairy Force, October 26th, 2018

 

The trak-ball is detected on startup, so you'll need to have it attached the whole time. I haven't implemented "reset technology" like all the kids use these days, that comes later.

 

Player 1 is on the bottom, player 2 on the top. You should be able to move either player around with the trak-ball. On my system, it feels really good, but as has been demonstrated, different controllers work differently.

 

I really just want to make sure that there's no drift, and that the controls feel good in general. I still have tweaking to do, and you can just ignore the joystick controls right now. I already know that those are way too sensitive.

 

A big thanks to anyone who has time to test this. I really want to nail this trak-ball stuff.

fairy_force.bin

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