It is very simple demonstration how to use Carambola as rover platform with video feedback. It could be nice toy to build in couple of hours.

I used very simple hardware setup. Key components are motor controller, 47:1 gearmotors, wheels, UVC webcam supported by mjpg_streamer and of course Carambola.

• Webcamera - just plug to USB port.
• Motor controller - connect to Carambola serial port. Use 2(TX) and 5(GND) pins. (see diagram below)
• Motors - see diagram below. Connect 2 motors in parallel.

• Build image with video support (see mjpg_streamer)
• Flash fresh image to Carambola (where to start)
• Setup wireless connection Wifi intialization
• Set system password (we will need this later for ssh access)

passwd root

• install package for video streaming

opkg update
opkg install mjpg-streamer

• edit /etc/config/mjpg-streamer if you like. Default settings works fine.

config mjpg-streamer core
      option device           "/dev/video0"
      option resolution       "400x200"
      option fps              "25"
      option port             "8081"
      option enabled          "true"

opkg install ser2net

• edit /etc/ser2net.con - comment all lines at the end of file and add this one

2002:raw:600:/dev/ttyS1:115200

• edit /etc/rc.local file to add ser2net autostart functionality

ser2net
exit 0

• Now you are able to connect to Carambola's serial port via telnet 2002 port.
• You can now reboot your Carambola to see if everything works.

reboot

• open favorite network stream player (I have tested vlc and chrome web browser - both worked) and paste url http://192.168.0.112:8081/?action=stream
• For VLC make sure you setcaching to 0ms instead of 1200ms (default) to reduce video lag

• To test if robot responds to commands download this quick program which sends these commands directly to motor controller
  • Forward 0x8A, SPEED, 0x8D, SPEED
  • Backwards 0x88, SPEED, 0x8E, SPEED
  • Left 0x88, SPEED, 0x8D, SPEED
  • Right 0x8A, SPEED, 0x8E, SPEED
• Before you start playing, you should press setup button. It sends safety configuration to motor controller
  • Serial port idle timout = 0.25s 0xAA, 0x0A, 0x04, 0x03, 0x01, 0x55, 0x2A

This quick example illustrates how to interface motor controller and webcam. Further you could connect these items to build autonomous vehicle.

• gps
• counter on all wheels
• sonar
• robotic arm
• lights
• wifi booster
• volt meter
• wider angle lens
• smaller (lipo battery)

• I ordered 47:1 gear motor (285 RPM), which is still a bit to fast. So, if you plan to replicate this by your self, consider buying germotor with 75:1 or even 99:1 ratio.
• After you reboot Carambola, connect to it using ssh and type ser2net this will enable communication to motor controller.
• It is good idea to close all electronics and put external led's to indicate wireless signal level and other status signals.