STEP/DIR Pass through

[gsherwin74]

How hard would it be to pass the Z step and direction signal from the main cnc controller board through the THC controller board? Thought is the main cnc controller (based on GRBL running on an UNO) will control the Z axis for homing, setting pierce height, then dropping down to cutting height, all the while sending those step and direction pulses through the THC board to end up going out to the stepper driver. Once cutting height has been reached, the THC would take over sending step and direction pulses to the stepper driver. An M-code (such as coolant on) could be used to send a signal from the main cnc controller to the THC to let it know when to take over. Once the cut is completed, the main cnc controller resumes command lifting the Z axis and moving the next cut location to restart again.