This is a Raspberry Pi HAT that implements a PC-style parallel port. GPIO pins are organized as data, status, and control registers. The HAT includes a buffer chip that converts from the GPIB 3V3 logic to signals that conform to IEEE 1284. A 26 pin IDC header on the board connects to your DB25 connector. A parport-gpio driver and device tree overlay integrate the HAT with the Linux parport driver stack.

I wanted to use a parallel port based cooled astronomy camera, but preferred to use the compact and low-power Raspberry Pi over a PC at the telescope. Parallel ports are simple devices. Why not build one?