Jon's Place

Thursday, December 7, 2006

On-board versus Wireless

One of the interesting things about building an advanced robot today is there are so many choices available. I've been participating in a thread on RoboSavvy with another person who wants to use the Bioloid kit for building an autonomous robot, but doesn't want on-board processing. Instead, he wants a high-speed wireless link to the Bioloid bus over Wifi, so he (and his students) can program and operate the robot from a PC.

So, to accomplish that, you would need:
In order to get a high-speed link (1 Mbps) with the Bioloid bus from your PC, you would need to use the SPI connection between the Wifi module and the ATMega128. Apparently, the robostix can't run SPI as a master, so I'll have to use a different ATMega128 board, like the one linked above. That would require a re-factoring of the code my brother Dave wrote that runs on the robostix, so that it would listen to the SPI port rather than the hardware UART. The nice side effect to this is it would leave the extra hardware UART free, for me means I could plug the digital camera directly into that, and have frames from it feed back over the wireless link as well.

The only real issue with this kind of a setup versus using a gumstix is the latency introduced with the wireless link. Since I'm going to be doing dynamic balancing, having low-latency response is important. Having the brain run on my laptop instead of on the gumstix would hugely simplify development of it, and I could go a lot further, given the massive amount more memory, processing power, and hard drive space I would have available.

Everything would be easier to code and debug, because I could have interactive user interfaces that run in real-time along side the controller, to monitor exactly what it is doing and what it is seeing. A down side is the Wifi module chews power (probably close to half an amp), so the battery won't last as long. But batteries aren't hard to swap on a robot like this, so I don't view that as a huge downside.


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