i needed to clarify (gates between resistor and diode):I would put a resistor on this side of the diode to make sure that io pin isn't shot.
yes, something like that will work - and it works in some gate's output stages too.
you just need to make sure that you can live with the charge-up time set by the 500ohm resistor and the gate capacitance - again, not a problem for low frequency stuff we do.
12v----resistor----diode----pic io pin
.....................|
.....................|
................fet gates
as for gate charge, it needs to be accounted for regardless of frequency. scope the gates @ PWM frequency to see the rise and fall times, etc. i typically drive high current brushless dc motors @ 30Hz and keep them at minimum 20-30% PWM after startup and drive them between startup-100% PWM. but as i mentioned before, the freqency chosen really depends on the characteristics of the motor.
the OP should also be weary of the flyback voltage and decaying oscillation between the motor coil and the fet's drain. the osciallation occurs due to motor inductor and fet's drain capacitance. with my setup i saw a 30kHz decaying ring so i squashed it with a small ceramic cap and resistor to ground. also had a 36v zener to help protect the fet, etc. without snubber you'll easily see this on the scope.
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