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
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.
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 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 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 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”.
http://comedi.org
git://comedi.org/git/comedi/comedi.git
git://comedi.org/git/comedi/comedilib.git