> Factor number two is that 1% at 200 Hz is 50us

I'd suggest 50us would be very very dim indeed and I really do
doubt the occassional few usec disturbance would be discernible

After all, it's 4950us until the next 'on' refresh, so the "20%" error
isn't part of the 'on' pulse. The disturbance could well be in the 'off'
time. If I were doing it, and the s/w has noted a delay is in effect,
then you might have something like

pulse - 4960us - pulse - 4940us - pulse

where the s/w compensates for the 10us delay by shortening the
next interval by 40us. The overall error is 0.2% in the position of
the pulse within the 5000us period. Assuming only 1 LED is lit
that is ; you'd take off processing time for selecting and lighting
each additional LED

As this is all being done under interrupt, there shouldn't be any
noticeable delay anyway with a fast processor. 40MHz is a cycle
time of 100ns, 500 instructions per 50us

Easy to test with a single LED

Joe
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