I just hooked up my Scroll Phat HD to my Raspberry PI zero and it was amazingly easy. I want to add a few more components to what I’m building. I want to add a relay switch and wanted to see if there are an free GPIO pins I can still use. Or does the board use all the PI pins.
Thats is correct 2, 3, 5 & 9. 3 and 5 are i2c which is a shared bus. You can connect other i2c devices to those pins as long as no two devices share the same i2c address.
The scroll phat uses 0x74: for the IS31FL3731