fix regressions, remove obsolete description of isapnp support

This commit is contained in:
Frank Mori Hess 2003-07-08 23:51:29 +00:00
parent f98e8f792e
commit 5cc75f5efe
3 changed files with 51 additions and 47 deletions

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@ -27,76 +27,50 @@ the <command>comedi_config</command> command. (As root of course.)
Here is an example of how to use the command (perhaps you should read
its <command>man</command> page now):
<screen>
/usr/sbin/comedi_config /dev/comedi0 ni_atmio 0x260,3
PATH=/sbin:/usr/sbin:/usr/local/sbin:$PATH
comedi_config /dev/comedi0 labpc-1200 0x260,3
</screen>
This command says that the &ldquo;file&rdquo;
<filename>/dev/comedi0</filename> can be used to access the &comedi;
device that uses the <parameter>ni_atmio</parameter> driver, and that
device that uses the <parameter>labpc-1200</parameter> board, and that
you give it two run-time parameters (<literal>0x260</literal> and
<literal>3</literal>). More parameters are possible, for example to
discriminate between two or more identical cards in your system.
</para>
<para>
If you want to have the board configured in this way every time you
boot, put the line above into a start-up script file of your Linux
boot, put the lines above into a start-up script file of your Linux
system (for example, the
<filename>/etc/rc.d/rc.local</filename> file), or in the system-wide
&comedi; configuration file <filename>/etc/comedi.conf</filename>.
You can, of course, also run this command at a command prompt.
<filename>/etc/rc.d/rc.local</filename> file), or for PCMCIA
boards the appropriate place is the /etc/pcmcia/comedi script.
For non-PCMCIA boards, you can also arrange to have your driver
loaded and comedi_config run with by adding a few lines
to /etc/modules.conf (see the INSTALL file for the comedi
kernel modules). You can, of course, also run comedi_config
at a command prompt.
</para>
<para>
This tutorial goes through the process of configuring &comedi;
for two devices, a
<literal>National Instruments AT-MIO-16E-10</literal> (which has the
driver mentioned above), and a
<literal>National Instruments AT-MIO-16E-10</literal>, and a
<literal>Data Translation DT2821-F-8DI</literal>.
</para>
<para>
The NI board is plug-and-play, and the <command>man</command> page
tells you that you need to configure the PnP part of the board with
<command>isapnptools</command>. The <command>isapnptools</command>
package is a little cryptic, but the concepts are simple. Once you've
learned how to use it, you can settle on a
<filename>/etc/isapnp.conf</filename> file such as this:
</para>
The NI board is plug-and-play. The current ni_atmio driver
has kernel-level ISAPNP support, which is used by default
if you do not specify a base address. So you could simply
run comedi_config as
<screen>
# ANSI string --&gt;National Instruments, AT-MIO-16E-10&lt;--
(CONFIGURE NIC2400/10725401 (LD 0
(IO 0 (BASE 0x0260))
(INT 0 (IRQ 3 (MODE +E)))
# (DMA 0 (CHANNEL 5))
# (DMA 1 (CHANNEL 6))
(ACT Y)
))
comedi_config /dev/comedi0 ni_atmio
</screen>
<para>
(This file also contains a few lines about overall configuration and
about the sound card that happens to be in the same computer.)
Currently, the driver doesn't use DMA, but it may in the future, so
the DMA lines are commented out. It has been reported that the
National Instruments board does not always work with interrupts other
than IRQ 3, and that the device ignores the IRQ and DMA information
given here. However, keep the information here to remind yourself that
the numbers aren't arbitrary.
</para>
<para>
The <command>man</command> page
explains that the option list is supposed to be
&ldquo;<literal>(I/O base),(IRQ)</literal>&rdquo;, so use the same
numbers as in <filename>/etc/isapnp.conf</filename>, i.e.,
<literal>0x260,3</literal>.
</para>
<para>
For the <literal>Data Translation</literal> board, you need to have a
list of the jumper settings; these are given in the &comedi; manual
section about this card. (Check first to see whether they are still
correct!)
correct!)
The card discussed her is a <literal>DT2821-f-8di</literal>. The
<command>man</command> page of <command>comedi_config</command> tells
you that you need to know the I/O base, IRQ, DMA 1, DMA 2. However,
@ -131,7 +105,7 @@ So, the appropriate options list is:
</screen>
and the full configuration command is:
<screen>
/usr/sbin/comedi_config /dev/comedi1 dt2821-f-8di 0x200,4,,1,1,1
comedi_config /dev/comedi1 dt2821-f-8di 0x200,4,,1,1,1
</screen>
The differential/single-ended number is left blank, since the
driver already knowns (from the board name), that it is

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@ -998,7 +998,37 @@ data structure, and has no function at present.
</section>
<section>
<title>
Anti-aliasing
</title>
<para>
If you wish to aquire accurate waveforms, it is vital that you use an
anti-alias filter. An anti-alias filter is a low-pass filter used to
remove all frequencies higher than the Nyquist frequency (half your sampling rate)
from your analog input signal
before you convert it to digital. If you fail to filter your input signal,
any high frequency components in the original analog signal will create
artifacts in your recorded digital waveform that cannot be corrected.
</para>
<para>
For example, suppose you are sampling an analog input channel at a rate of
1000 Hz. If you were to apply a 900 Hz sine wave to the input, you
would find that your
sampling rate is not high enough to faithfully record the 900 Hz input,
since it is above your Nyquist frequency of 500 Hz. Instead, what you
will see in your recorded digital waveform is a 100 Hz sine wave! If you
don't use an anti-alias filter, it is impossible to tell whether the 100
Hz sine wave you see in your digital signal was really produced by a
100 Hz input signal, or a 900 Hz signal aliased to 100 Hz, or a 1100 Hz
signal, etc.
</para>
<para>
In practice, the cutoff frequency for the anti-alias filter is usually
set 10% to 20% below the Nyquist frequency due to fact that real filters
do not have infinitely sharp cutoffs.
</para>
</section>
</section>

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@ -1,4 +1,4 @@
<!-- <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V3.1//EN" "docbook/dtd/3.1/docbook.dtd"> -->
<!-- <!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook V3.1//EN" -->
<section id="comedi-comedilib-h">
<title>