Page 359 - Hacking Roomba

340 Part III — More Complex Interfacing

This problem is compounded in OpenWrt because embedded systems have their own set of
restrictions. Of the several webcam drivers in Linux, the driver for the SPCA5XX chips seems
to have the best support under embedded Linux. This driver, called spca5xx, works well in
more than 100 webcams, with new ones being added regularly. The author, Michel Xhaard, has
even created an embedded version of the driver, called spca5xx_lite. This small driver is
only for those webcams that support JPEG streaming, a feature where the camera does the
JPEG compression and the driver needs to do very little to make an immediately viewable
image. Currently, 83 webcams support this mode and thus are compatible with spca5xx_lite.
This is the driver that is used here.
If you’re lucky, you have an old webcam sitting around that works with spca5xx. If not, there
are many to choose from. One of the cheapest is the Creative Instant webcam (see Figure 15-7),
available for about $25.

Visit http://mxhaard.free.fr/spca5xx.html for a complete list of cameras and their
level of support. See http://mxhaard.free.fr/embedded.html for information about
spca5xx_lite.

For great tutorials on doing interesting things with OpenWrt, including a great tutorial on get-
ting spca5xx cameras working, see Macsat at www.macsat.com/. Macsat’s tutorial was
indispensable for this section and his compilations of the spca5xx drivers and tools that are
used here. The http://roombahacking.com/ site mirrors them as a convenience.

FIGURE 15-7: A creative instant webcam