Hi all. I've been playing around with software PWM controlling some
LEDs. Problem is, as the eye's response to brightness isn't linear, when
I simply control the LEDs brightness using an 8 bit value (with no
compensation) they don't appear to dim smoothly. So my thought was to
take the 8 bit value, use it as an index into a lookup table which would
give me a higher bit value (ie a 12 or 14 bit).

Here is the problem (as I see it anyways). If I increase the bit
resolution of my PWM, the frequency will have to go down (as the PIC is
already running at full speed. yes, I could go to an SX chip...I know).
So, is there a resolution vs speed balance that anyone has reached that
gives optimal frequency and smoothness of the dimming? Also, how do you
choose the values for the lookup table? Most commercial theatrical
dimmers use a "modified S curve" which is essentially the integral of
the area under a sine wave (I think). I'm sure if I had Maple or
something (and knew how to use it) I could divide the area into 256
sections and come up with the proper values for the lookup table. But
since I don't have access to this high powered math software, what are
my options? Plotting out by hand seems only an invitation for
frustration.

Ideas welcome.

Thanks,

Josh
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