The rt-stepper project provides a USB CNC controller solution. Most CNC controllers are designed to be driven with a PC parallel port. The rt-stepper solution replaces the parallel port with USB. Users can convert their existing parallel port CNC controller into a USB CNC controller. Designers can integrate the hardware into there own CNC controller. The PC side software is based on the popular EMC2 software at www.linuxcnc.org. EMC2 provides 4-axis support, a complete gcode interpreter, a trajectory planner, a GUI front-end, backplotting, and more. The best part of the solution is since the rt-stepper hardware provides the real time step pulses, you can now run EMC2 on Linux, Mac OS, and Windows.