Jon's Place

Sunday, December 10, 2006

Wireless

I've decided, as a result of my previously mentioned conversation, to make MicroRaptor wireless, without using the gumstix at all. The past couple weeks of playing with the gumstix has reminded me of what a pain it is to develop on a truly headless platform. I'm going to interface a Wifi module over SPI to an ATMega128 board, which will interface to the Bioloid bus. The SPI can interface at 1 Mbps, so the connection from my laptop to the Bioloid bus will be at least 1 Mbps throughout.

The only real worry about this setup is the latency over the wireless link. If it proves to be too much, I will implement a force-driven actuator system on the AVR, so the latency from the PC will not seriously affect things. I may end up doing that anyways, so that the actuators act more like series elastic actuators.

This decision has several interesting side effects. One is that I can use a wireless camera, with a USB video capture card. That allows me to capture much higher resolution video, at decent frame rates, with full color. Another is that it will be much simpler to control the robot directly, say by using a joystick, which will help when I am working on the motion control.

Of course, the most interesting side effect is I can, assuming that the mechanicals work out the way I hope they will, delve much further into what I'm really trying to accomplish with this robot and its successor - real hard-core artificial intelligence.

3 Comments:

  • Hey, very interesting stuff you have going on here. Im considering a bioloid kit for myself next year as well. One thing that i dont understand is why are all the hobby robotics guys still stuck on 8-bit micros ? I mean, im an embedded developer myself and my main platform to work on is 32bit ARM9, with optional DSPs etc. The chips dont cost more than your average 8-bit micro but performance and platform convenience difference is huge. You normally run full linux on these, program in C++ and use wide array of ready-made free software libraries.

    So the first thing that im going to do is stick an ARM7 or ARM9 linux SBC into that thing. When that falls short in processing performance, you can always fall back to wireless setups. WDYT ?

    By Blogger kert, At December 17, 2006 at 12:12 PM  

  • Just to give an idea,
    http://robots.net/article/1873.html
    New Low-Cost ARM9 SBC With WiFi

    By Blogger kert, At December 17, 2006 at 12:20 PM  

  • kert,

    Its an interesting module, but it costs $150 in quantity 1000, which means it will be at least $300 in single quantity. That's way more than a typical 8-bit micro.

    I know you can get 32 bit ARM7 micros for around the same price as a put-together 8 bit micro board, but for most of what I do, its way overkill. I actually have a Tini2138, which I may end up using instead of the ATMega128 when I move the force-control code onto the robot.

    Anything that runs full linux won't do hard real-time the way you can with an 8-bit micro running on the metal.

    Personally, I prefer doing development on a PC, and with the Wifi module, I can develop and run with the same machine. Headless linux boards, while convenient for deployment, are a royal pain to develop complex systems on.

    By Blogger Jon Hylands, At December 17, 2006 at 4:43 PM  

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