[avr-chat] PWM, to fast!

[gecko gecko]

Hi people,

I've just got the hang of PWM (i think) but it turns out that its just to fast! I need about 30Hz frequency and to vary the duty cycle from full(ish) to about 1/3. The idea is to control the speed of a fan by the PWM.

Am i right in thinking:    8MHz / 128prescalar = 62500kHz is the slowest PWM I can make?

If so I need to write a software PWM, and so any pointers in the right direction would be apreciated. (i think timers are involved, but I don't know here to start with timers, its taken me long enough to get PWM's down!)

Thanks guys.

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