NateW is currently certified at Master level.

Name: Nate Waddoups
Member since: 2002-02-16 22:38:44
Last Login: 2006-10-05 06:33:27

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Homepage: http://www.natew.com/

Notes:

Ultimately I would like to build a walking robot with which to harass neighborhood canines, but that's not a pressing need. Meantime, I am working on robot simulation software - see http://www.natew.com/juice/ for details.

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  • Lead Developer on Juice

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Did some experimenting with bluetooth and bandwidth, by creating a BT server that receives 40-byte packets and replies with 40-byte packets, similar to what the Gumstix is doing on my biped, but without any actual processing. My hope was to get more bandwidth by using a raw bluetooth socket instead of building on top of the bluetooth serial port profile, but alas, the SPP overhead is apparently negligible.

I can up the packets to 80 bytes and still get 60 frames per second between my desktop and my laptop, but on the gumstix I am stuck at about 15 fps even with the raw socket approach.

On a related note, one of my Gumstix is booting Windows CE now, so the above testing was all done with C#. Unfortunately, debugging requires either USB or ethernet and my biped has room for neither, so I need to figure out a way around that (ActiveSync over bluetooth?) before I reflash the Gumstix in the biped to boot CE as well.

Currently the CE-on-Gumstix stuff is only usable by people with Platform Builder (Microsoft's CE development suite), which is pretty expensive. But with any luck, that will change in the not-too-distant future.

Turns out I didn't kill the servo controller after all. Far as I can tell, it was just getting confused by the ~3 volts leaking through the voltage regulator while the Gumstix/Robostix combo booted. I guess by the time the Gumstix turned on the Robostix voltage regulator, the servo controller had given up due to the brown-out. The more recent Gumstix boot loader turns on the voltage regular almost immediately, and the servo controller is happy.

The gyro/accelerometer board isn't mounted yet (hence the open space above the battery pack), and I want to move the battery cells out to the arms, and there's a big mess of wires hanging out the back, but the pile of parts looks like a robot again. It's just hanging from the test stand in those pictures, but hopefully it will stand on its own before too long.

I put my biped back together, and got all of the servos moving (just one at at time) via bluetooth, and they I killed the servo controller right before Robothon. The new servo controller got here last week, but I want to re-do the power distribution before I install it. It would be nice to be able to turn the servo controller on and off from the Gumstix (and maybe the servos themselves too). I'm still thinking that over...

Question for Bram V:


How does Lucy balance laterally? I can't see any side-to-side weight shift - is the lateraly movement very small, or is Lucy's top end attached to something? Great video by the way, the leg movements are very smooth.

It was a bit of a struggle to get bluetooth working right on the Gumstix, and it paid off. The Gumstix forms a bluetooth personal area network with my laptop when the Gumstix boots, so I can SSH into it for administration and monitoring. The laptop can also open a serial connection via bluetooth to send commands to the Gumstix, which forwards them to the servo controller. I don't even have to be in the same room. :-)

The robot is spread out all over my workbench as I write this, but it's almost time to put it back together again.

The biped mechanics are mostly done, other than a bit of fit-and-finish work:

Front View

Rear View

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