What are your steps per unit and Velocity? that will determine the kernel speed you will need. ie 20,000 steps per unit x 100 IPM Velocity would equal 2,000,000 pulses per minute. Divide by 60 to get pulses per second and that would be 33,333 pulses per second (Hz ) or 33.333KHz so you would in this case need 35KHz kernel.
Hood