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>Control and Measurement Device Interface</I
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>This section assumes that you have successfully compiled and installed
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> software, that your hardware device is in your computer,
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and that you know the relevant details about it, i.e., what kind of
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card it is, the I/O base, the IRQ, jumper settings related to input
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NAME="CARDCONFIGURATION"
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>2.1. Configuration</A
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>Before being able to get information from a DAQ card, you first have
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> core kernel module which device you have, which
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driver you want to attach to the card, and which run-time options
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you want to give to the driver. This configuration is done by running
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> command. (As root of course.)
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Here is an example of how to use the command (perhaps you should read
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>PATH=/sbin:/usr/sbin:/usr/local/sbin:$PATH
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comedi_config /dev/comedi0 labpc-1200 0x260,3</PRE
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This command says that the <SPAN
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> can be used to access the <ACRONYM
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device that uses the <VAR
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you give it two run-time parameters (<VAR
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>). More parameters are possible, for example to
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discriminate between two or more identical cards in your system.</P
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>If you want to have the board configured in this way every time you
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boot, put the lines above into a start-up script file of your Linux
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system (for example, the
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>/etc/rc.d/rc.local</TT
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> file), or for PCMCIA
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boards the appropriate place is the /etc/pcmcia/comedi script.
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For non-PCMCIA boards, you can also arrange to have your driver
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loaded and comedi_config run with by adding a few lines
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to /etc/modules.conf (see the INSTALL file for the comedi
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kernel modules). You can, of course, also run comedi_config
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at a command prompt.</P
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>This tutorial goes through the process of configuring <ACRONYM
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>National Instruments AT-MIO-16E-10</VAR
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>Data Translation DT2821-F-8DI</VAR
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>The NI board is plug-and-play. The current ni_atmio driver
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has kernel-level ISAPNP support, which is used by default
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if you do not specify a base address. So you could simply
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>comedi_config /dev/comedi0 ni_atmio</PRE
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>Data Translation</VAR
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> board, you need to have a
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list of the jumper settings; these are given in the <ACRONYM
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section about this card. (Check first to see whether they are still
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The card discussed her is a <VAR
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you that you need to know the I/O base, IRQ, DMA 1, DMA 2. However,
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> driver also recognizes the
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differential/single-ended and unipolar/bipolar jumpers. As always,
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the source is the final authority, and looking in
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tells us that the options list is interpreted as:</P
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>(... TO BE FILLED IN ...)</P
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>So, the appropriate options list is:
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and the full configuration command is:
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>comedi_config /dev/comedi1 dt2821-f-8di 0x200,4,,1,1,1</PRE
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The differential/single-ended number is left blank, since the
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driver already knowns (from the board name), that it is
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differential. Also the DMA numbers are left blank, since we
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don't want the driver to use DMA. (Which could interfere
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with the sound card...)
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Keep in mind that things commented in the source, but not in
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the documentation are about as likely to change as the weather,
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so put good comments next to the following line when you put
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it in a start-up file.</P
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>So now you have your boards configured correctly.
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Since data acquisition boards are not typically well-engineered,
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> sometimes can't figure out if the board is actually there.
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If it can't, it assumes you are right. Both of these boards
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are well-made, so <ACRONYM
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> will give an error message if it
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can't find them. The <ACRONYM
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> kernel module, since it is a part
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of the kernel, prints messages to the kernel logs, which you
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can access through the command <B
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>/var/log/messages</TT
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Here is a configuration failure (from <B
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>comedi0: ni_atmio: 0x0200 can't find board</PRE
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>When it does work, you get:</P
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>comedi0: ni_atmio: 0x0260 at-mio-16e-10 ( irq = 3 )</PRE
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>Note that it also correctly identified the board.</P
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NAME="GETTINGINFORMATION"
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>2.2. Getting information about a card</A
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>So now that you have <ACRONYM
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> talking to the hardware, try to
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>. Here's some pretty low-level information, which can
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sometimes be useful for debugging:</P
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>cat /proc/comedi</PRE
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>On the particular system this demonstration was carried out, this
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>comedi version 0.6.4
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0: ni_atmio at-mio-16e-10 7
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1: dt282x dt2821-f-8di 4</PRE
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>This documentation feature is not well-developed yet. Basically, it
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currently returns the driver name, the device name, and the number of
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> directory, there is a
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>, which provides information
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about each subdevice on the board. Its output can be rather long,
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if the board has several subdevices.
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Here's part of the output of the <VAR
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>National Instruments</VAR
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board (which is on <TT
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>demo/info /dev/comedi0</B
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version code: 0x000604
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driver name: ni_atmio
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board name: at-mio-16e-10
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number of subdevices: 7
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type: 1 (analog input)
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number of channels: 16
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>The overall info gives information about the device; basically
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the same information as <TT
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>This board has seven subdevices. Devices are separated into
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subdevices that each have a distinct purpose; e.g., analog
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input, analog output, digital input/output. This board also
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has an EEPROM and calibration DACs that are also subdevices.</P
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> has more information about the device than what is displayed
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> doesn't currently display
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