This is test driven application for controlling a motor using avr-libc. While avr-libc is harder to use to control a motor than Wiring (Arduino) or similar libraries, it isn't wildly difficult if you read the documentation and any of the excellent tutorials out there.
Most importantly, programs written with avr-libc make it really easy to test drive the code and mock hardware interfaces, so I can define and test behavior easily without having to go through a constant but slow build->deploy->run cycle.
The motor controller assumes a pully mechanism which starts with the rope at its furthest extent from the pully.
The motor is run in the Up direction, and the number of cycles consumed is recorded, until the limit switch is closed.
When the switch is closed, the motor reverses direction and continues until the same number of cycles have expired as were used to pull the rope up. In this manner the mechanism should continue lowering and raising the pulley for roughly the same distance each time. Some variation is expected because the system does not contain any encoders, or use stepper motors which can closely control the number of revolutions.