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Sat Dec 25 01:45:59 EST 2010

Dithered PWM

Probaly re-inventing something, but the idea is this: instead of
sending out a minimal switching varying duty cycle pulse wave, send
out a _permuted_ version, and change the permutation on each duty
cycle.

This shouln't be too difficult when using an easy to compute
permutation, i.e. an LFSR.

For an LFSR it works like this: generate the sequence in the usual way
as n-bit numbers, and send out the carry result of comparing to the
desired output signal average.  For the next cycle, switch
polynomials, or even just start at a different inital point.  Anything
that's cheap such that the next period and the previous one are not
correlated.

This really should work.  How fast can it be implemented on a PIC?  Is
it actually better than simply using dithered sigma/delta?




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