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====== Comedi - The Linux Control and Measurement Device Interface  ======

[[http://www.comedi.org|Comedi]] provides a common Linux interface to certain DAQ hardware, \\
typical PCI digital and analog I/O cards and is actively developed since 1998.

It consists of 
  * Linux drivers
  * Comedilib
  * Kcomedilib

==== Drivers ====

The newest sources for the Comedi and driver modules\\
are available from the official Git repository.

  git clone git://comedi.org/git/comedi/comedilib.git
  
Use //autotools// to generate the //configure// script

  ./autogen.sh
  
To display all available options

  ./configure --help
  
[The following assumes you're in a maintenance chroot and are\\
installing the modules directly to the diskless system.\\
If you want to build and install the drivers to a different \\
directory, for example '/srv/diskless/fec/arch/L866_64/lib/<kernel-version>/'\\
you have to specify --with-modulesdir=<DIR>]

Assembling the Makefile for 64-bit Linux 3.10.82-rt89 with RT preempt patch
  
  ./configure --with-rtlinuxdir=/usr/src/kernels/3.10.82-rt89 \
              --with-kernel-release=3.10.82-rt89 --with-rpm-target=x86_64

Compiling

  make
  
Installing

  make install

This will install the modules to

  /lib/modules/<kernel-version>/...
  
where kernel-version is 3.10.82-rt89 in this example.


=== Linux In-Tree Comedi Support ===

Comedi and available drivers are also integrated into the Linux kernel \\
since 2.6.30, located in the experimental staging tree.\\

This might be the best choice unless the kernel version of choice\\
lacks required hardware support or contains bugs stopping its use.\\
In that case we should use the out-of-tree Git version as described above.\\

To enable Comedi and build the //comedi// module, setup the \\
kernel configuration as follows:

  Device Drivers [*]
      Staging drivers [*]
          Data acquisition support <M>
This ensures the built of the comedi module only.\\
To actually make use of the supported hardware,\\
the comedi //driver(s)// need to be set to build.\\

Taking the [[ds:io_addi_data_cards|ADDI-DATA I/O PCI card 1648]] for example,\\
activate the //Comedi PCI drivers// section and set the appropriate driver. 

              Comedi PCI drivers [*]
                  ADDI-DATA APCI_16xx support <M>

This will built the driver module addi_apci_16xx,\\
which depends on the comedi module. \\

When loaded, lsmod shows something like:

  comedi                 46649  1 addi_apci_16xx

Every device gets a separate //comedi[0-9]+// node in the device tree.\\
Assuming only one card in this example

  crw-rw---- 1 root root 98, 0 Aug  4  2015 /dev/comedi0
  
To access the device, use the library Comedilib for user-space applications\\
or Kcomedilib for real-time kernel modules making use of Comedi hardware.

==== Comedilib ====

Comedilib needs to be installed manually either via \\
the latest stable release tarball from the Comedi page
  wget http://www.comedi.org/download/comedilib-0.10.2.tar.gz
(At time of writing 0.10.2 was the latest stable release)
or by checking in out from the Git repository
  git clone git://comedi.org/git/comedi/comedi.git
  
The Git checkout requires to generate the //configure// script
using //autotools//

  ./autogen.sh

Hint: Depending on the autotools version, it might be required
to delete or comment the AM_PROG_AR macro in configure.ac!

To display all available options

  ./configure --help

Afterwards compile and install it via

  make
  make install
  
Once the drivers are properly loaded\\
an overview of all supported Comedi devices\\
can be received from

  > comedi_board_info

  overall info:
    version code: 0x00074c
    driver name: addi_apci_16xx
    board name: apci1696
    number of subdevices: 3
  subdevice 0:
    type: 5 (digital I/O)
    flags: 0x00030000
    number of channels: 32
    max data value: 1
    ranges:
      all chans: [0,5]
    command:
      not supported
  subdevice 1:
    type: 5 (digital I/O)
    flags: 0x00030000
    number of channels: 32
    max data value: 1
    ranges:
      all chans: [0,5]
    command:
      not supported
  subdevice 2:
    type: 5 (digital I/O)
    flags: 0x00030000
    number of channels: 32
    max data value: 1
    ranges:
      all chans: [0,5]
    command:
      not supported 
    
==== Kcomedilib ====

Kcomedilib provides the Comedilib interface to the kernel space.\\
This is useful when writing real-time kernel modules that need\\
access to Comedi devices.

The //kcomedilib// module is automatically built with the external\\
comedi package (see above). The intree version requires manual\\
setting of the appropriate kernel config under "Comedi misc drivers".

==== Resources =====

=== Comedi Webpage ===
http:%%//%%comedi.org \\

=== Git Targets ===
git:%%//%%comedi.org/git/comedi/comedi.git \\
git:%%//%%comedi.org/git/comedi/comedilib.git
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