I am writing a stepper motor control, which needs a frequency of at
least 5kHz (5000 motor steps per second) in "hand-driven" mode. You
can drive per keyboard and joystick. With keyboard there is no
problem, but the joystick is too slow. I like to know if there is a
faster code to get the position of the joystick.
The program works like this. Getting the joystick position at program
start. Save this value. Then I have a loop, which checks if the actual
joystick position is different to the saved position. If it is
different the stepper motors do one step. The Z-axis is controlled by
the joystick buttons. The move of the joystick is displayed on the
screen. (I removed this for testing, an therefore I think it is the
call of the interrupt, which makes the program slow.)
Here is some information of the code.
I am using TP 5.5 and OS is MS-DOS 5.0 . Variables are global. The
program runs in 640 x 480 points at 16 colors. Computer is 286.
VAR joy_x, joy_y, joy-status : WORD;
    register : REGISTERS;
PROCEDURE get_joystick_position;
BEGIN
        register.ah := $84;
        register.dx := 1;
        INTR($15,register);
        joy_x := register.ax;
        joy_y := register.bx;
        register.ah := $84;
        register.dx := 0;
        INTR($15,register);
        joy_status := register.ax;
END;

If you would give me a solution with assembler or inline code, please
add a comment in every line, because I never learnd this.

Thank you for reading.

All IIRC : a joystick is a cheap device, intended for games; ISTR that
it consists, per channel, of a variable resistor and a capacitor, and
its position is determined by using a digital threshold circuit to
detect its time constant; this takes time (not even constant time!?).

It may be worthwhile to open up the joystick, get direct access to the
resistors, and build a better circuit to measure the settings - perhaps
drive it through a constant-current diode, and measure the voltage with
an 8-bit ADC parallel-connected to the PC.  Or serial-connected; a COM
port will go quite fast, and you don't need to read every character.

Now I have an other question. You use much of this "short cuts" in
your postings, like IIRC or ISTR. Some of them I do not understand.
Where can I find a list of this "short cuts"?

Thank you for your time and advice.

regards

From my news-use.htm :
TOOTKA (tootka = Terms One Ought To Know About) is an old list of acronyms :
<A HREF="ftp://ftp.demon.co.uk/pub/doc/general/tootka.txt">FTP demon.txt</A>,
<A HREF="http://www.orbital.co.za/tootka.htm">HTTP za.htm</A>;
try also another, vast, list at
<A HREF="http://www.astro.umd.edu/~marshall/abbrev.html">HTTP umd.edu</A>.
An online computer dictionary can be found at
<A HREF="http://wombat.doc.ic.ac.uk/">Imperial College</A> (?), London.
Or see FYI18.

To what I suggest, alas, you really do need experience of some sort in
electronics.  If I still had the facilities to build and test one, I  
might be able to describe it so that it could be copied; or if you were
experienced, you could work from such suggestions.  But as is, the
combines risk of damage or failure is too great.  Perhaps if you were to
ask in a local newsgroup, you could find someone nearby to work with?

My page pc-urls.htm has a number of general references to use of serial
& parallel ports, but the serial port link is marked as gone :-(

PC <A HREF=
"ftp://rtfm.mit.edu/pub/usenet/news.answers/pc-hardware-faq/"

The <A HREF="ftp://ftp.phil.uni-sb.de/pub/staff/chris/The_Serial_Port">Serial
Port</A> (Gone? Where?)

"The <A HREF="http://www.lvr.com/ibmlpt.txt">document</A> (FNF)
contains a full description of using the parallel port this way," (Gone?)

The <A HREF=
"http://www.strangecreations.com/strange/library/hardware/parallel.txt">
Parallel Port</A> (FNF).
There may be another parallel port FAQ?

Kris Heidenstrom's Parallel Port
<A HREF=
"http://home.clear.net.nz/pages/kheidens/ppmfaq/khppmfaq.htm">mini-FAQ</A>.

Jan Axelson's <A HREF="http://www.lvr.com/">Lakeview Research</A> :
<I>"The source for information and tools relating to parallel ports,
RS-232 and RS-485 serial communications, 8052-Basic microcontrollers,
and making printed-circuit boards."</I>

"Interfacing to the IBM-PC Parallel Printer Port", Ian Harries,
<A HREF="http://www.doc.ic.ac.uk/~ih/doc/par/">IC</A> : links and
details.

Here's a thought : the standard joystick drivers are likely to have been
written long ago, for slow PCs.  IF the joystick circuit is as I think,
and if you were able to reduce the capacitor, you might be able to run
it faster on a modern machine with RDTSC.

regards

Then your only problem is how to program it. I messed around with a 68705 a
few years back and it had software in ROM for programming the onboard EPROM,
so you don't necessarily need to have an EPROM programmer (depends on the
chip).

If a chip with built-in ADC is too expensive or hard to find in your local
shops, there are versions with a serial port at least, which you could use
as an interface to an ADC. A quick web search threw up
http://www.kullen.rwth-aachen.de/users/dschlich/esp95/index.html as an
example (although you might want a faster ADC: 100s conversion time? Must be
a typo.)

(You'll probably need some sort of buffer so you get reasonable RS232
voltages but there's chips for that too, e.g. MAX220-MAX249 from Maxim)

Thank you for reading.

But many mice have two channels; for each, the ball bears on a wheel
which turns a slotted disc within the jaws of an opto-detector.
Assuming that you are willing to risk the lives of a few mice, you could
dismantle the mechanics entirely, and craft another means of moving
suitable slots within the jaws.  Note that the opto must detect
direction, so must have two sensors per channel.  It's probably easier
to re-do the mechanics completely.  It may not be necessary to match the
slots in size.  They need not, I think, be actual holes, just something
alternately transparent & opaque; you could make your own by [computer-]
drawing and photographic reduction.

ISTM that a mouse, plus standard drivers, works fast enough to keep up
with a human being; and that you perhaps want the motor to do what would
be necessary to drive a mechanical mouse in the same way as the screen
pointer behaves.?

I want to say "Thank you very much" for all your help.