The two Wabbit FB boards shown below, distributes ground and IOPi input pins to the Wabbit optic isolators. When a turnout command is received by the Wabbit, the clear or thrown optic isolator pulls the IOPi input pin to ground (or let the line go high), causing an IOPi interrupt. In response to the interrupt the Raspberry Pi sends a sensor status change (<Q nn> or <q nn>) to the laptop.

NOTE: on one board 2 pin numbers are in red to help me remember later that I miss wired the interface board.

Wabbit Feedback board - 1

Wabbit Feedback board - 2

The connections between the Wabbit feedback/status outputs, Wabbit feedback boards and IOPi HAT are shown below. Each turnout controlled by a Wabbit has two optic isolators, one for clear and one for thrown. Cables connect each Wabbit to the feedback boards above, where wiring is combined into cables to the IOPi HAT, part of the Raspberry Pi stack (3).

Wabbit Feedback wiring