Car robot project
 

Ubuntu linux

Linux kernel: http://www.rcn-ee.com/deb/kernel/beagle/jaunty/v2.6.29-58cf2f1-oer33/ 


SDHCI: timeout during data transfer

This patch was necessary for me: http://kerneltrap.org/mailarchive/linux-kernel/2008/9/23/3388144. I don't know which SD card I have but my bug was not covered by http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap-2.6.git;a=commit;h=603ded16a308d0a7a17738c973e3c8cbcd5db7dd.

Webcam

Finally chose a webcam. Logitech QuickCam E 2500. Philips spc230nc was rejected due to higher price and lower quality. E2500 has great form-factor and convenient stand to put it on the car. To enable the webcam I looked on this thread http://forums.quickcamteam.net/showthread.php?tid=310 and recompiled the kernel (https://help.ubuntu.com/community/Kernel/Compile) after adding a line

{USB_DEVICE(0x046d, 0x089d), .driver_info = SENSOR_MC501CB},

to the appropriate place in drivers/media/video/gspca/zc3xx.c

Webcam examples here: http://www.seismo.ethz.ch/linux/webcam.html 

Power consumption

Wifi: 400mA. Isn't it too hot?

Beagleboard: 300(idle)-390mA. Is there some power management missing? After around 5 minutes idle drops to 240mA.

GStreamer

Server command:

gst-launch-0.10 v4l2src device=/dev/video0 ! video/x-raw-yuv,width=320,height=240,framerate=\(fraction\)10/1 ! ffmpegcolorspace ! jpegenc quality=50 ! multipartmux ! tcpserversink port=8222

Client command:

gst-launch-0.10 tcpclientsrc host=192.168.1.104 port=8222 ! multipartdemux ! jpegdec ! videoscale ! video/x-raw-yuv, width=640, height=480 ! xvimagesink

This setup eats only 50 % of CPU power on BB. There are some problems tho: 1) "libv4lconvert: Error decompressing JPEG: unknown huffman code" bug 2) green line on the bottom 3) some frames are corrupted

Battery

I try to use 4 cells of GP 2700mah rechargables. We need 800mA current. Problem is big voltage drop on contacts (sometimes 0.2V) which makes a difference. First time charged batteries gave only 5 V on this load, 4.8 on the beagleboard. After 1 hour only 4.6 V on the beagleboard. The nice thing is the batteries are pretty stable, so we do not need voltage regulator (which eats more voltage).