16 Feb 2002 ROB.T.   » (Master)

I've finished a rough-draft model (UML) of the base module, and guess what? I'll be using one microcontroller, the Atmel AT90S8535 for each leg. The definitive factor was the number of ADCs required - 5 per leg - to gather all the leg information. I've also decided to build one complete leg and use my Atmel emulator to test the concept.

After laying it all down on paper, it looks like the base module - which is basically the 8 legs and battery pack - is going to have 12 processors. The disadvantages of this approach - money and battery power. The advantage is I can break the tasks into small hardware/software components that are a lot easier to handle. Also I shouldn't have the timing headache I might encounter trying to get everything to work on one big processor with a lot of I/O. Lastly this leaves room for future expansion like more sensors on the legs.

The motor controller I've decided to use is the L298. The LMD18200 looked real good, but since my processors can perform all the functions that the `200 provides with the exception of temperature handling, I opted for the much cheaper motor controller with 2 H-bridges in it. This is an important decision since I want to order chips this Monday.

For the CAD part of the robot, I've gotten the individual axis components drawn out in 3D, but have yet to put the stuff together.

As a side note I want to include logging, error checking, and testing in all modules. I still want all of the intricacies of getting a leg moving to be transparent to the robot system with most functions stored for the base module, at the base module. If all goes well, the base module promises to be very robust or at the very least helpful at troubleshooting itself.

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