Re: Timing problem with serial port and/or cocoa drawing (please ignore!)
Re: Timing problem with serial port and/or cocoa drawing (please ignore!)
- Subject: Re: Timing problem with serial port and/or cocoa drawing (please ignore!)
- From: Hank Heijink <email@hidden>
- Date: Tue, 10 Oct 2006 16:44:35 -0400
Embarrassing moment here...
After double-checking the whole situation on the old computers (Mac
OS 9.2.2, Blue G3 with Keyspan SXPro card and PowerPC 7200 with same
system), it turns out the delay has always been there... I'm sorry, I
should have checked more carefully before posting. It is pretty much
certain that it isn't a cocoa problem, but a problem of the tablet
itself.
Again, my apologies! I hope I didn't waste anybody's time yet.
Hank
Hank Heijink
www.hankheijink.com
email@hidden
On Oct 10, 2006, at 4:10 PM, Hank Heijink wrote:
I've been trying to solve the following problem for a couple of
days now, and I'm stuck. I'm writing an application for research
purposes that involves reading coordinates from a big (3 by 5 ft)
digitizing tablet and projecting the tablet-controlled cursor on a
two-way mirror above the tablet through a ceiling-mounted Epson
projector. Eventually the cursor movement will be partly invisible,
rotated, scaled -- it's all about how people use visual feedback in
movement.
What happens is that the display cursor lags behind the tablet
cursor. If I move the tablet cursor at a steady pace (about 0.5 m/
s), the display cursor follows it at about an inch distance and it
catches up when I stop moving. I can't figure out where the delay
comes from... I hope it's just something stupid that I did, but I
can't figure it out.
<snip>
The tablet communicates like a modem with a serial port, and sends
coordinates at just over 160Hz. I've tested this on a MacBook
2.0GHz with the tablet connected to a Keyspan USA-28X serial-to-USB
converter, and on a Dual G4 450MHz with a Keyspan SXPro PCI Card.
The projector is connected to the MacBook with Apple's VGA
converter, and the G4 has two ATI Rage graphics cards.
We used to connect this tablet to a Keyspan SXPro card on Mac OS
9.2.2 on a blue G3, and that worked fine.
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