This low cost automation system takes advantage in the use of the open-hardware solution Basic Input
Output Elements (BIOE), which is used as IO-subsystem for the Raspberry PI.
BIOE usually depends on a PC's printer port (LPT). The Raspberry PI is not a PC and therefore does not have an LPT, but digital IO (GPIO).
To close the gap between the Raspberry PI and BIOE, a printer port's behavior is emulated by own drivers using the GPIO of the Raspberry PI.
The control law runs on Realtime Linux on the PI using BIOE as counterpart to a industry PC's multi function DAQ add-in card.
The possible sample frequency of the Raspberry PI could be increased up to 1000 Hz - meeting hard realtime constraints concerning both jitter and IO time.

The following video shows this solution using this Raspberry PI based automation system as controller for laboratory model Ball On Wheel.