[SiriusHardware]

The screen printing for the 40-way connector indicates that the connection is for a Pi-Zero. Out of the box, the Pi Zero doesn't usually come with anything soldered into the GPIO port pads so the fastest and easiest way to dedicate one for this purpose is to solder a 2 x 20 (40 way) female IDC PCB connector to the underside of the Zero / Zero W. (image 1).

However you can actually connect the interface to any 40-pin Pi which has male pins fitted and pointing upwards, including a Pi Zero or Pi W, by using a short one-to-one female to female extension lead (image 2).

Although I usually use a Pi Zero W, I have also tested the interface and 'support software' on a Pi 3 connected as shown in the second image.

Taking things further, if you don't mind writing or adapting software yourself you can also use some other microprocessor or logic device to drive the interface, as long as it can output either a 3V3 or 5V0 common supply, and as long as its individual I/O pins can sink enough current to 0V to power one LED each. When the interface is operating, no more than two of the 13 optocoupler LEDs are ever powered at the same time.