On Fri, Dec 03, 2010 at 07:54:57PM -0800, Kirk Wallace wrote:
> 
> I really had no idea if the memory would be enough. I would have worked
> on it until I went blind in one eye.

Oh, it's enough for what you want to do now. But ISTR a home switch +
index filter, on the other thread. It can do that too, if pins can be
found. But then there's the extra functionality we just have to have,
when we're nearly finished. ;-)

> In looking for something else (small h-bridge) I found this (and
> ordered):
> http://www.sparkfun.com/products/9147 
> 
> There is even some code to use as a reference:
> http://www.sparkfun.com/Code/AVR-Stick_v12.zip 

Ah, they use the USB frame timing to calibrate the on-board RC
oscillator.

I saw USB transmit code, but nothing for receive (i.e. for setting
watchdog timing.) Ah, your last site has projects involving USB output.

> http://www.obdev.at/products/vusb/projects.html 

The "small H-bridge" design I spotted there is another very low power
example, using the L293D. I'd at the very least put some DPAK FETs on a
PCB, instead. I'm not sure I'd trust the shoot-through provisions of one
of those amateur designs. If not using half-bridge drivers with
dead-time, the ATtiny26's timer1 has complementary outputs with
dead-time fixed at one prescaler clock interval.

However, if you want to do motor PID, then a reasonable swag of the 1k
instruction space is eaten. Incidentally, the ATmega8 (used the same
design) is old. The ATmega48 is a scalable replacement.

> I feel a project cascade coming on.

The trouble escalates when you succumb do doing "just one more design,
with just one more layout" to economise on the shipping from the cheap
PCB places in Asia. :-)

Erik

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