47 lines
2.1 KiB
HTML
47 lines
2.1 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
|
<HTML>
|
|
<HEAD>
|
|
<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
|
|
<TITLE>Linux I/O port programming mini-HOWTO: Hints</TITLE>
|
|
<LINK HREF="IO-Port-Programming-8.html" REL=next>
|
|
<LINK HREF="IO-Port-Programming-6.html" REL=previous>
|
|
<LINK HREF="IO-Port-Programming.html#toc7" REL=contents>
|
|
</HEAD>
|
|
<BODY>
|
|
<A HREF="IO-Port-Programming-8.html">Next</A>
|
|
<A HREF="IO-Port-Programming-6.html">Previous</A>
|
|
<A HREF="IO-Port-Programming.html#toc7">Contents</A>
|
|
<HR>
|
|
<H2><A NAME="s7">7. Hints</A></H2>
|
|
|
|
<P>If you want good analog I/O, you can wire up ADC and/or DAC chips to
|
|
the parallel port (hint: for power, use the game port connector or a
|
|
spare disk drive power connector wired to outside the computer case,
|
|
unless you have a low-power device and can use the parallel port
|
|
itself for power, or use an external power supply), or buy an AD/DA
|
|
card (most of the older/slower ones are controlled by I/O ports). Or,
|
|
if you're satisfied with 1 or 2 channels, inaccuracy, and (probably)
|
|
bad zeroing, a cheap sound card supported by the Linux sound driver
|
|
should do (and it's quite fast).
|
|
<P>With accurate analog devices, improper grounding may generate errors
|
|
in the analog inputs or outputs. If you experience something like
|
|
this, you could try electrically isolating your device from the
|
|
computer with optocouplers (on <EM>all</EM> signals between the computer
|
|
and your device). Try to get power for the optocouplers from the
|
|
computer (spare signals on the port may give enough power) to achieve
|
|
better isolation.
|
|
<P>If you're looking for printed circuit board design software for Linux,
|
|
there is a free X11 application called Pcb that should do a nice job,
|
|
at least if you aren't doing anything very complex. It is included in
|
|
many Linux distributions, and available in
|
|
<A HREF="ftp://sunsite.unc.edu/pub/Linux/apps/circuits/">ftp://sunsite.unc.edu/pub/Linux/apps/circuits/</A> (filename
|
|
<CODE>pcb-*</CODE>).
|
|
<P>
|
|
<P>
|
|
<HR>
|
|
<A HREF="IO-Port-Programming-8.html">Next</A>
|
|
<A HREF="IO-Port-Programming-6.html">Previous</A>
|
|
<A HREF="IO-Port-Programming.html#toc7">Contents</A>
|
|
</BODY>
|
|
</HTML>
|