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 a 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 then reads the port and sends a sensor status change (<Q nn> or <q nn>) to the laptop.

In the images below the numbers in the circles show the connection between the cables from the Wabbits and the bits on the IOPi bus. Left and right of the 3-pin headers are the Wabbit number (1-6) and the Tortoise number (1-12). Above and below are the Wabbit J5/J6 feedback pin numbers. The Wabbit and IOPi are connected so that the odd IOPi pins are ways the CLEAR bit, even pins are the THROWN feedback. The middle pin (black dot) are connected to IOPi ground and pins 2 and 4 of Wabbit J5/J6.

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