Thursday, February 12, 2009

Some work done - week 5

With Jake, my 12-year old friend who finally got to work with me on this more, I built an interface board between the Roomba and a PC. The idea was that if a PC could talk to the Roomba, we could then make sure that the Roomba can be controlled by the Linksys Open-WRT box (and also diagnose the problems I was seeing with the vacuum bot). The work we did involved a schematic found in "Hacking Roomba" book which had some basic directions on how to build the interface board. As all the interface board parts came in from Digi-key earlier in the week (and had other purchased from Radio Shack), we could do this. Jake and I spent almost 14 hours on the project over a night and a day, and had to deal with a lot of challenges and delays, mostly related to my lack of prototyping and soldering skills (this was one of my few soldering projects I've ever worked on and probably the most sophisticated, definately since High School). At the end of it all one of the PC's showed an echo of the text back (using a test wiring and not from the Roomba), however I want to verify this again soon so I wasn't mistaken, as it didn't happen on a Windows XP PC, that had the communications software recommended to use in the book.

For the week I wanted to work on a new web page, requirements, and even start coding but this time and effort on the interface board perhaps was too much over two days. I've had the need and luxary of being able to take a break and I've been able to do other things that are valuable (like look for a job more) . Also I was a bit sick but I'm looking to pick back up again. The thing I want to do next is to send the commands through the Linux PC RS-232 port and see a response from the Roomba, and try to get my planning and requirements done, so I can actually start coding.

Photo links:
Summary of tasks done:
  • Built an interface board according to specification with the addition of a connector for the DIN 6 cable. This interfaced the 16 Volt battery to power the MAX232 chip. The MAX232 chip converted the TTL data lines to the RS-232 data line voltage levels that were compatible with the RS-232 port on my PC.
  • Used a 9V "wall wort" power supply to test the circuit by adding a male DIN 6 connector on it and looping the RX/TX lines as recommended in the book
  • Converted the DIN 6 to be compatible with the DIN 7 / 8 ports - by brute force and experimentation
  • Downloaded communications software to test the interface board. The Linux PC seemed to show an echo but not the Windows XP PC. I need to get a new cable to diagnose the problem on the XP PC or figure out how to stay with the Linux system.
  • The software from the book didn't run on the XP PC as expected but it didn't matter as the RS-232 port didn't seem to echo back anything.

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