Wednesday, July 05, 2006


Done with shaft encoding...

I got the firmware for the little yellow G4 and the AS5035 shaft encoder doing what I wanted last night. We've got direction and speed control via PWM and feedback on both via the AS5035 chip. The shaft encoder chip is everything that Vik and Adrian said it was.

I have some L298N H-bridge chips on order, but my supplier seems to have gone on Summer holiday, so I'm stuck there unless I want to reorder from Mouser or Digipen. Using what I know to run the Frankenmotor seems to be the next logical step, except that the L298N's that I need for that are not in hand yet.

If Randy stays gone for a few more days I'll see if I can get interrupt-driven serial comms going and maybe try out those Hamamatsu chips for limits detection.

One thing that's become rather obvious is that I want to do more firmware programming than there is memory in the 16F628A. I'm currently up to 1.4K out of 2K available. I've ordered some 16F877A's which have 8K and cost roughly twice what the 16F628A does. The only drawback to those is that you absolutely have to use an external clock chip with the 877A and those run cost as much as a 16F628A. Anyhow, that lets me to use 20 MHz which gives me 5 times the processing power.

I'll be swapping over to the 18F chip family pretty quickly, though. Those come with up to 64K memory and on-board 8 MHz crystals at about US$4-5/unit. They also have lots of port pins and A/D channels to boot. They also give me USB capability.

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