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Processor

Overview.

While i'm quite happy building my own microcontroller modules the main processor for this robot will have to be bought if i am to have the processor power i will need for mapping and navigation.

I deliberately made the chassis of this robot versatile enough to take a wide variety of processors.

 

Requirements.

Here are some of the requirements in an on board computer:

  • Low power. This rules out all current x86 type boards as they are all far more power hungry than other architectures. Less than 5Watts would be ideal.
  • Runs Linux (or similar OS).
  • The chassis is controlled via USB (although it would be easy to convert to serial or UART).
  • I will need to connect a camera to the main processor. USB cameras are the cheapest way of doing this.
  • The robot should be controllable via wireless ethernet so the main processor must be capable of interfacing some sort of wireless ethernet card. (USB is again an obvious choice here.)
  • etc...

 

Options.

Here are some of the options i have found. They all have at least one USB host port ans run some version of Linux.

  • NSLU2. Pros: runs Debian. Cons: higher power draw than i would like. Small RAM for large image manipulation.
  • Gumstix. Pros: high performance to power ratio. Cons: non standard Linux distro. stupid board design.
  • Hammer Pros: Low power draw. Cons: non standard Linux distro.
  • Fox Board Similar specs to the NSLU2.
  • TS-7260 Pros: Super low power. Runs Debian. Got to get round to buying me one of these...
  • other suggestions welcome.... (comments a the bottom of page.)

 

The NSLU2.

This is the only platform i have tested in the bot so far.

Rather than explain what the NSLU2 is i'll just quote from the NSLU2 community website:

http://www.nslu2-linux.org/wiki/FAQ/WhatIsANSLU2

"The Linksys NSLU2 , a.k.a. the "Slug", is a small low cost network storage device from Linksys. Its main purpose is to serve as a network file server: on one side of the Slug, you connect one of two USB hard disks, on the other side your wired computer network at home or a small office. The disks can then be made available to that network, to computers running Linux, Mac OS or Microsoft Windows (and probably quite a few stranger platforms too).

The Slug can be flashed with a new firmware to make it what it essentially is: a small Linux computer. And from there, the sky seems to be the limit!"

As it runs Debian it is simple to install new packages on. With a 2G USB flash drive plugged in i never have to worry about limited disk space. Having USB host ports means i can plug in USB webcam and wireless network card.

I'm not going to go into detail here on how to set up an embedded Linux system. There are far better sites than this out there for that.

Picture above shows NSLU2, flash memory stick, USB hub, USB wireless card and USB webcam.

Picture above shows NSLU2 installed in chassis.


Testing

For testing purposes i run a web server on the NSLU2. I have a CGI written in Python that writes to the virtual serial port created by the USB driver.

This allows me to display a web page with buttons to control the bot.

Obviously this is far from the finished control interface but it does let me have fun driving it around....

So while at face value this robot appears to be very similar to my previous LMbot it has the fundamental difference that the web server is running on board the bot.








mrdunk(at)gmail.com

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