brushless servos without hall commutation

Hi,

I have a number of brushless servos I've collected to build some cnc
machines. All of them have optical encoders of some resolution, but
none have hall-effect sensors for commutation.

What I am wondering is if there is any reason (I can't think of any) why
I couldn't divide the optical encoder output with a PIC or something
to get a faked hall-effect commutation output I could use for a
generic controller.

Has anyone faked the hall-sensor arrangement somehow?

bluecoast