[Coco] Joystick jitter in OS9

[CoCoList for Color Computer Enthusiasts]

CoCoList for Color Computer Enthusiasts wrote:
>
> Got a question for you guys,
> Does anyone know a good method of removing the "joystick jitter" in OS9 L2?
> In certain postions, my (black Tandy) joystick or deluxe color mouse will start "jumping" about 3 or 4 pixels, back and forth. It will occassionally do this while trying to position it on an item.
> I can loose some resolution, that's not an issue as I'm already skipping about 6 or 7 pixels on a 640x192 screen to get full screen access. I do not need "pixel by pixel" resolution.
> I could possibly trim it to every 4 or 5 chars (8 pixels per char horiz, 7 vert) if needed. It doesn't seem to jerk vertically. I haven't noticed if it does this with the Hi-Res interface as I've had it disconnected lately.
> This is not a major issue... it just "bugs" me.
> I'm using C for programming and the mouse read is the standard mouse packet system call.
>
> Anyone got any ideas?
>
>
> Bill Pierce
> "Today is a good day... I woke up" - Ritchie Havens

Bill,

Unless you have tested your joystick with an ML routine in Basic and found there 
is no jitter, give some thought to the pots having deteriorated with age.

I have some jitter with my deluxe joysticks and have found that that same jitter 
can be seen with an ohm meter. That means the routines that read the pots are 
not bad but the pots themselves are bad.

If these pots are wire wound and not carbon tracks, you could try cleaning them 
with a deox spray. I can't tell by looking at them what type they are.

About the only thing you can do via software is either calculate an average 
reading or do what Basic does. Basic will look at 10 readings and report the 
result when two match or if none match use the last reading.

Robert
robert.gault at att.net