Richard,
We've got an RS232 joystick which is currently moving a pedestal quite
nicely.
I have not done the initial work on it so can't remember the specifices, but
I believe it sends digital commands. Also, it was not too expensive, but I
can't remember the price, but can find out.
So, BOTTOM LINE, if you'd like more info on our use of this joystick. Let
me know and I'll refresh my memory (which I need to do anyway since have to
integrate all this soon).
Janet Estabridis
Electrical Engineer
NAWC Code 473E00D
Building 31440 Room 1017
China Lake, CA 93555
[EMAIL PROTECTED]
(760) 939-2896 FAX (760) 939 -3075
> -----Original Message-----
> From: [EMAIL PROTECTED] [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, May 31, 2000 1:34 PM
> To: Basham, Richard R
> Cc: Andrew Price; '[EMAIL PROTECTED]'; Tomasz Motylewski;
> [EMAIL PROTECTED]
> Subject: Re: [rtl] RTLinux and joystick
>
>
> I very much expect that a USB joystick would solve the problem. The game
> port
> is a casette tape period device.
>
> On Wed, May 31, 2000 at 12:28:02PM -0700, Basham, Richard R wrote:
> > I am not familiar with your desired final product but I would mention
> that joysticks usually have resistive potentiometers and therefore could
> be used to feed the input to an ADC board. This would probably get around
> some of the hardware/driver issues associated with the inexpensive I/O
> architecture of the game port. Obviously, this reduces the generic PC
> portability and increases the complexity.
> >
> > I wonder how using the game port differs from the same joystick with
> USB? Anyone?
> >
> > Just a thought,
> > Rich
> >
> > > ----------
> > > From: [EMAIL PROTECTED][SMTP:[EMAIL PROTECTED]]
> > > Sent: Wednesday, May 31, 2000 10:04 AM
> > > To: Andrew Price
> > > Cc: Tomasz Motylewski; [EMAIL PROTECTED]
> > > Subject: Re: [rtl] RTLinux and joystick
> > >
> > > On Wed, May 31, 2000 at 02:56:56PM +1000, Andrew Price wrote:
> > > > I ran a very small real time application whose sole purpose was to
> > > > toggle
> > > > a bit of the parallel port every 100us.
> > > >
> > > > In the long term I will use this to schedule events etc etc..
> > > >
> > > > The application I am working on also has need for the joystick.
> > > >
> > > > When I ran up the current joystick driver for linux, and in
> particular
> > > > the
> > > > joystick driver for the microsoft (cringe) sidewinder it caused the
> > > > system
> > > > to lock up. If I slowed the rate of the real time process. to one
> toggle
> > > > every 2ms
> > > > the joystick operates normally.
> > > >
> > > >
> > > > I used the example program for latency testing for the parallel port
> > > > along with
> > > > 'jstest' an example that is packaged with the current joystick
> driver
> > > > for linux.
> > > >
> > > >
> > > > Can anyone explain why the high rate of the real time process
> affects
> > > > what the joystick,
> > > > a common garden variety process is doing?
> > >
> > > A quick look at the sidewinder driver shows this amusing comment:
> > >
> > > /*
> > > * js_sw_read_packet() is a function which reads either a data packet,
> or an
> > > * identification packet from a SideWinder joystick. Better don't try
> to
> > > * understand this, since all the ugliness of the Microsoft Digital
> > > * Overdrive protocol is concentrated in this function. If you really
> want
> > > * to know how this works, first go watch a couple horror movies, so
> that
> > > * you are well prepared, read US patent #5628686 and then e-mail me,
> > > * and I'll send you an explanation.
> > > * Vojtech <[EMAIL PROTECTED]>
> > > */
> > >
> > >
> > > and then this cli protected code:
> > > do {
> > > bitout--;
> > > u = v;
> > > v = inb(io);
> > > } while (!(~v & u & 0x10) && (bitout > 0)); /*
> Wait for first falling edge on clock */
> > >
> > > So it tries to turn off interrupts and do a busy wait for a falling
> edge. I bet these
> > > last for near millisecond periods -- with a 100us RT thread
> interrupting the device
> > > is not going to work well at all.
> > >
> > > Sorry. One solution is to get a better joystick. Another is to run on
> a SMP board.
> > >
> > >
> > >
> > >
> > > --
> > > ---------------------------------------------------------
> > > Victor Yodaiken
> > > FSMLabs: www.fsmlabs.com www.rtlinux.com
> > > FSMLabs is a servicemark and a service of
> > > VJY Associates L.L.C, New Mexico.
> > >
> > > -- [rtl] ---
> > > To unsubscribe:
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> > > ---
> > > For more information on Real-Time Linux see:
> > > http://www.rtlinux.org/rtlinux/
> > >
>
> --
> ---------------------------------------------------------
> Victor Yodaiken
> FSMLabs: www.fsmlabs.com www.rtlinux.com
> FSMLabs is a servicemark and a service of
> VJY Associates L.L.C, New Mexico.
>
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