Note: see page 20 of the manual (
http://www.keil.com/dd/docs/datashts/philips/user_manual_lpc214x.pdf) for
EINT details.

So, in diging into the details of the LPC2148, I've found that it has only 4
external interrupt lines. Each interrupt can be configured to trigger from a
couple of pins (and maybe the same interupt from multiple pins, not sure
yet). With respect to when the external interrupts trigger, this is
configurable, but in reading thru the manual, it looks like you can only set
it to positive or negative going edge, not on change (on change would be
nice for the quadrature encoder).

Ideally we'd have 5 external interupts, some of which would trigger on
change (quadriture ints), others on positive edge (hall sensors), however I
don't think were going to have that luxury with the LPC2148.

Technically, four rising edge interupts would work (3 hall sensors, 1
quadriture), however that means less resolution on the RPM of the table,
which will imply reduced ability for the PID loop to smothly react at low
RPM.

What are your thoughts on this. Theres a million ways to do this, but what
has the best mix of quick, easy, maintainable and will satisfy our
functional requirements?

Thoughts?


Thanks,
-Dave
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