Interfaces to the Comedi data acquisition library for normal (streaming) analog input and output.Comedi (linux control and measurement device interface) provides hardware drivers to many data acquisition boards with a common library interface. The RELACS Comedi plugins access data acquisition boards by means of the Comedi library.
For general information about Comedi and a list of supported devices see http://www.comedi.org
Content
Install comedi
On recent linux distributions comedi modules are already in the Linux kernel. You only need to install the comedilib library
sudo apt-get install libcomedi-dev
and to set the permissions as described in Setting up udev permissions for Comedi device files. If your data acquisition board needs to be calibrated, you also need to install comedi_calibrate. This seems not to be available as a package, so you have to compile it yourself. See Comedi_calibrate for details.
If this does not work (some older versions did not provide some functions needed by the RELACS comedi plugins), or if you require the most recent version of comedi, you should reinstall the comedi drivers and the comedi library from scratch as described in the following sections.
You should install the comedi drivers and library prior to configuring RELACS, so that ./configure can detect the presence of the comedi library. If you install comedi later, simply run make again to detect comedi and compile the corresponding plugins for RELACS.
Linux kernel
In order to be able to install the Comedi drivers you need to have a kernel source tree that matches your running kernel image. Either compile your own kernel from scratch (section Compile your own kernel , takes some time), or make sure that you get a matching source tree for your kernel image (section Install sources for an existing kernel).
Install sources for an existing kernel
Get the soure and headers that matches your kernel. On Ubuntu/Debian you get the kernel source and header files matching your running kernel image by executing as root
cd /usr/src
apt-get install dpkg-dev
apt-get install linux-headers-`uname -r`
apt-get source linux-image-`uname -r`
If apt-get source tells you "E: You must put some 'source'
URIs in your sources.list" then you need to enable the source repositories for the package manager. For this open with your favorite editor /etc/apt/sources.list and the *.list files in /etc/apt/sources.list.d/. Remove the comments in front of the lines that start with "deb-src". Then run
to resynchronize the package index files with the new repositories. Now apt-get source should be able to download the kernel sources.
If apt-get source tells you "E: Unable to find a source package" then check which kernel sources are available:
apt-cache search linux-source
uname -r
choose the one that is closest to your installed kernel (uname -r), install and unpack that one:
apt-get install linux-source-3.13.0
tar xf linux-source-3.13.0.tar.bz2
After downloading the kernel source create a link to the kernel source:
ln -sfn <kernel-source> linux
where <kernel-source> is the kernel source installed by apt-get, e.g. a directory with a name like linux-source-3.13.0
Note that often the kernel source directory that you installed with apt-get has a different name than the name of the currently running kernel that uname -r returns. Use ls -rtl to list the directories in the /usr/src folder. The last one is the one that was added by apt-get source. Now you can cd into the kernel source directory
- Copy the kernel configuration file of your kernel image to the source:
cp /boot/config-`uname -r` .config
- Make sure the file
Module.symvers is also in your source. On Ubuntu/Debian you find it in the corresponding linux-headers directory: cp ../linux-headers-`uname -r`/Module.symvers .
- Run
make silentoldconfig
make prepare
make scripts
make \ silentoldconfig.
Compile your own kernel
- Get a vanilla kernel from http://www.kernel.org, e.g. http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.38.8.tar.bz2, place the tar file in
/usr/src and unpack it as root with cd /usr/src
tar xjvf linux-2.6.38.8.tar.bz2
linux-2.6.38.8 by the directory name of your new kernel source). Create a softlink to your kernel source ln -sfn linux-2.6.38.8 linux
cd linux
make, gcc, libncurses-dev, and zlib1g-dev packages are installed: apt-get install make gcc libncurses-dev zlib1g-dev
- Reuse your current configuration (replace
XXX by the name of your running kernel): cp /boot/config-XXX .config
make oldconfig
enter to all the (probably many) questions.
- Steps 3. to 6. describe the normal way to compile a linux kernel. On Debian systems there is an elegant alternative that is described in step 9. below. First, you configure your kernel by calling Possible settings you might want to change are:
- Processor type and features:
- Select your Subarchitecture Type (PC-Compatible) - this option does not exist for newer kernels
- Select the right Processor family (you find the name of your processor by looking at
/proc/cpuinfo, check "help" to find out, which Processor family you have to select)
- Select "Preemption Model (Preemptible kernel (Low-Latency Desktop))"
Leave the configuration dialog by pressing "Exit" until you are asked "Save kernel config?". Select "Yes".
- Then compile and install (as root) the kernel
make && make modules && make modules_install && make install
- Finally you might need to create a RAM disk image file, if
make install did not create a /boot/initrd-2.6.38.8 file already: cd /boot
update-initramfs -c -k 2.6.38.8
- Check the grub menu whether your new kernel was added.
- With
grub v2 (default since Debian Lenny) simply run the output of update-grub should mention your new kernel image. You can configure grub v2 by editing the file /etc/default/grub . To get the boot menu that you need to select the kernel you want to boot you should for example unset the GRUB_HIDDEN_TIMEOUT and set the GRUB_TIMEOUT appropriately in that file. For example: #GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT=10
/etc/grub.d/10_linux # if [ "$list" ] && ! $in_submenu; then
# echo "submenu \"Previous Linux versions\" {"
# in_submenu=:
# fi
update-grub to apply the changes.
- With
grub v1 (default up-to Debian Lenny) there should be an entry like this in /boot/grub/menu.lst: title Debian GNU/Linux, kernel 2.6.28.9
root (hd0,0)
kernel /boot/vmlinuz-2.6.28.9 root=/dev/sda1 ro quiet
initrd /boot/initrd.img-2.6.28.9
- Reboot the computer into the new kernel.
- Install third party kernel modules as well, like for example the ones for your graphics board. For your nvidia graphics board, download the driver from http://www.nvidia.com/Download/index.aspx?lang=en-us. Install it by calling
sh NVIDIA-Linux-x86_64-190.42-pkg2.run
sh NVIDIA-Linux-x86_64-190.42-pkg2.run -k 2.6.28.9-rtai -K
uname -r' would return if that kernel is running).
- On a Debian system there is an alternative to steps 3. - 6. for compiling a linux kernel. See http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Debian_Lenny_Compile_RTAI for more details. Do as root:
- Get the kernel-package
apt-get install kernel-package libncurses-dev
- Configure and build the kernel:
export CONCURRENCY_LEVEL=2 # set here the number of CPUs you have to speed things up!
make-kpkg clean
make-kpkg --initrd --revision 1.0 --config menuconfig kernel-image kernel-headers kernel-source
-j option to tell make how many processes can be run in parallel. See step 3. for hints on the configuration options.
- Install the kernel
cd ..
dpkg -i linux-image-2.6.38.8_1.0_amd64.deb linux-headers-2.6.38.8_1.0_amd64.deb
- continue with step 6.
Comedi
Kernel versions 2.6.30 onwards have an experimental in-tree Comedi implementation in the driver "staging" area. You can check whether it works for you by following the instructions of point 11 below. However, we recommend installing a current version of the comedi drivers.
Here are all commands that you can throw into a shell to completely install comedi:
# install all required packages:
apt-get -y install gcc g++ git autoconf automake libtool bison flex libgsl0-dev libboost-program-options-dev
# download comedi sources:
cd /usr/local/src
git clone https:
git clone https:
git clone https:
rm -r /lib/modules/`uname -r`/kernel/drivers/staging/comedi
# comedi:
cd /usr/local/src/comedi
./autogen.sh
./configure
make -j$(grep -c "^processor" /proc/cpuinfo)
make install
depmod -a
cp include/linux/comedi.h /usr/include/linux/
cp include/linux/comedilib.h /usr/include/linux/
# comedilib:
cd /usr/local/src/comedilib
./autogen.sh
./configure --prefix=/usr --sysconfdir=/etc
make -j$(grep -c "^processor" /proc/cpuinfo)
make install
# comedi_calibrate:
cd /usr/local/src/comedi_calibrate
autoreconf -v -i
./configure --prefix=/usr --sysconfdir=/etc
make
make install
# setup udev permissions:
addgroup --system iocard
echo 'KERNEL=="comedi*", MODE="0660", GROUP="iocard"' > /etc/udev/rules.d/95-comedi.rules
udevadm trigger
adduser $USER iocard
In the following the necessary steps are described in detail:
- Download the current
Comedi sources from the Git repository to /usr/local/src as root. apt-get install git
cd /usr/local/src
git clone https:
git clone https:
git clone https:
/usr/local/src and unpack them cd /usr/local/src
tar xzvf comedi-HEAD-*.tar.gz
tar xzvf comedilib-HEAD-*.tar.gz
tar xzvf comedi_calibrate-HEAD-*.tar.gz
- You may need to install the packages:
autoconf, libtool. apt-get install autoconf automake libtool
- Make sure that you are really running the kernel for which you want to install
Comedi! You can check with
- Remove the Comedi staging modules to avoid conflicts:
rm -r /lib/modules/`uname -r`/kernel/drivers/staging/comedi
- Change to the
comedi directory:
- Generate the configuration script by calling You may ignore warnings and reminders.
- Configure simply by calling in case you want to install
Comedi into your currently running kernel. If /usr/src/linux is not your running kernel, then call ./configure --with-linuxsrcdir=/usr/src/linux
/usr/src/linux replaced by the path to the sources of the kernel for which you want to install Comedi.
- Compile
make -j$(grep -c "^processor" /proc/cpuinfo)
- For some strange reason, the include files for kcomedilib
linux/comedilib.h and linux/comedi.h are not installed by Comedi to Comedi include files in Comedi include files to cp include/linux/comedi.h /usr/include/linux/
cp include/linux/comedilib.h /usr/include/linux/
- Check loading the Comedi module: If you do not get any error message, then the Comedi kernel modules were successfully compiled and can be loaded into the kernel.
- Check autodetection of your data acquisition board:
udevadm trigger
ls /dev/comedi*
ls command shows something like /dev/comedi0 /dev/comedi0_subd1 /dev/comedi0_subd12
/dev/comedi0_subd0 /dev/comedi0_subd11 /dev/comedi0_subd2
comedi* character device files, your board probably was detected. Run comedi_board_info /dev/comedi0
comedi_board_info and comedi_test are part of comedilib, see below). In case no /dev/comedi* device file shows up or comedi_test reported an error (E: comedi_open("/dev/comedi0"): No such device), your data acquisition board needs to be configured manually, using something like comedi_config /dev/comedi0 ni_mio_cs
/etc/init.d/boot.local file, so that the board is configured during startup of the system. For this you also need to tell comedi to create a /dev/comedi0 device file for you. Add the following line to /etc/modprobe.conf or /etc/modprobe.d/comedi.conf (the latter you have to create if the directory /etc/modprobe.d exists): options comedi comedi_num_legacy_minors=4
Comedilib
- You may need to install the packages:
autoconf, libtool, bison, flex. apt-get install bison flex
- Change to the
comedilib directory as root: cd /usr/local/src/comedilib
- Generate the configuration script by calling You may ignore warnings and reminders.
- Configure comedilib to be installed in
/usr/lib and /usr/include ./configure --prefix=/usr --sysconfdir=/etc
prefix. You may want to read –help as well. Pay attention to warnings and errors! You might need to install additional software first.
- Compile and install (as root)
make -j$(grep -c "^processor" /proc/cpuinfo)
make install
- In case
make fails with this error message: libtool: link: gcc -std=gnu99 -I../include -I../include -Wall -g -O2 -o .libs/comedi_test comedi_test-bufconfig.o comedi_test-cmd_1.o comedi_test-cmd_2.o comedi_test-cmd_3.o comedi_test-info.o comedi_test-insn_read.o comedi_test-insn_read_time.o comedi_test-inttrig.o comedi_test-lib.o comedi_test-
main.o comedi_test-mmap.o comedi_test-mode0_read.o comedi_test-select.o ../lib/.libs/libcomedi.so -lm
../lib/.libs/libcomedi.so: undefined reference to `nearbyint'
../lib/.libs/libcomedi.so: undefined reference to `floor'
collect2: error: ld returned 1 exit status
make[2]: *** [comedi_test] Error 1
make[2]: Leaving directory `/usr/local/src/comedilib/testing'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/local/src/comedilib'
make: *** [all] Error 2
libcomedi_la_LIBADD = -lm
lib/Makefile.am after the line libcomedi_la_LDFLAGS. Then run make clean
./autogen.sh
./configure --prefix=/usr --sysconfdir=/etc
make -j$(grep -c "^processor" /proc/cpuinfo)
make install
- You might further test your board using
comedi_test -t cmd_continuous
Comedi_calibrate
- You may need to install the packages:
autoconf, libtool, libgsl0-dev, libboost-program-options-dev. apt-get install libgsl0-dev libboost-program-options-dev
- Change to the
comedi_calibrate directory as root: cd /usr/local/src/comedi_calibrate
- Generate the configuration script by calling You may ignore warnings and reminders.
- Configure
./configure --prefix=/usr --sysconfdir=/etc
- Compile and install (as root)
Setting up udev permissions for Comedi device files
Once comedi is installed you also need to make sure that you (the user) have appropriate permissions for accessing the comedi device files. That is you need to be able to have read and write access to the /dev/comedi* files. One elegant way to achieve this to create a new group and tell udev to add the comedi device files to this group.
- Login as root.
- Create a new group "iocard":
- Add udev rules to the /etc/udev/rules.d directory:
echo 'KERNEL=="comedi*", MODE="0660", GROUP="iocard"' > /etc/udev/rules.d/95-comedi.rules
- Run to apply your new udev rules
- Add users to the "iocard" group:
adduser \<username\> iocard
<username> is a member of the iocard group and and has sufficient permissions to access the data acquisition boards through Comedi.
Resize Comedi buffer
To set the Comedi internal buffers to 640kB do as root:
comedi_config -r /dev/comedi0
comedi_config --read-buffer 640 --write-buffer 640 /dev/comedi0 ni_pcimio
Maybe this should go in /etc/rc.local or to some udev postprocessing rule.
Calibrating analog input and output
For calibrating analog input and output you should run comedi_calibrate once in a while. comedi_calibrate writes a file to /usr/var/lib/comedi/calibrations that contains the calibration parameter. The ComediAnalogInput and ComediAnalogOutput plugins read this file and apply the calibration.
For hardware calibrated boards (like NI E-Series boards) do
comedi_calibrate --reset --calibrate -f /dev/comedi0
For software calibrated boards (like NI M-Series boards) do
comedi_soft_calibrate -f /dev/comedi0
You may want to read the man page of comedi_calibrate.
