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It is possible to plug and use a webcam on the Freerunner. This is a very rough list of the steps required to do so with Debian Lenny installed.

The webcam used to perform this example is a Philips SPC620NC, using the [UVC] driver.

The method described here is still rather ugly, feel free to improve it.

Make it work on a PC

To be safe, you just first ensure the webcam works on a regular PC, and Linux in particular. This will minimise the problems you are likely to face (though it may not eliminate them altogether). The regular documentation applies:

• to UVC-compliant webcams

Add video support to the kernel

The 2.6.24 kernel is provided without video input support enabled. There is a way to add the necessary modules without recompiling everything:

• download the source code for the kernel:

# wget http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.24.tar.bz2

• make sure you have bzip2 and development tools installed:

# apt-get install bzip2 gcc make libc6-dev libncurses5-dev

• uncompress it in /usr/src:

# cd /usr/src
# tar -xjvf $OLDPWD/linux-2.6.24.tar.bz2

• fix links bluntly in /lib/modules:

# ln -sf /usr/src/linux-2.6.24 /lib/modules/2.6.24/build

• initialize the kernel sources with the current configuration:

# cd /usr/src/linux-2.6.24
# gzip -dc /proc/config.gz > .config
# make oldconfig          # just say "n" to power management debugging support

• add video support:

# make menuconfig

Basically, look for "Device drivers", "Multimedia devices", then enable "Video For Linux", "Video For Linux API 1", "Video For Linux API 1 compatible Layer", "Video capture adapters" as modules. If the driver for your webcam is found in the kernel already, also enable it there.

• compile the relevant kernel modules:

# make drivers/media/video/v4l1-compat.ko
# make drivers/media/video/v4l2-common.ko
# make drivers/media/video/videodev.ko

• load the modules:

# insmod drivers/media/video/v4l1-compat.ko
# insmod drivers/media/video/v4l2-common.ko
# insmod drivers/media/video/videodev.ko

The errors encountered while loading modules can be obtained with the "dmesg" command. They are typically also logged in /var/log/messages.

Compile the UVC driver

To obtain and compile the latest source tree for the driver:

# apt-get install subversion
# svn checkout svn://svn.berlios.de/linux-uvc/linux-uvc/trunk
# cd trunk/linux-uvc
# make

And if all goes well:

# insmod uvcvideo.ko

Add the device node

In our case, the relevant device node was not created automatically. Here's how to do so:

# mkdir -p /dev/v4l
# mknod /dev/v4l/video0 c 81 0

Plug the camera itself

The Freerunner needs to run in USB host mode in order to do this. A special USB cable (or gender changer) is necessary to do so.

Again, you can use the command "dmesg" to verify that the camera is properly recognized.

Install and try a viewer

A good webcam test application is luvcview. You can install and test it this way:

# apt-get install luvcview
# luvcview -f yuv -d /dev/v4l/video0

Known problems

• the resolution was limited to 160x120 with our Philips SPC620NC

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