@henk-herck - thanks for your reply and suggestions. I changed the pins to output and set them as high, but unfortunately it didn't change the outcome. In the end I soldered some wire into the OpenSprinkler's expansion board to help me get to that row of pins which allowed me to work around my issue. I'd never really looked at the Orange Pi range before and went a bit down a rabbit hole looking at them yesterday. They're quite interesting and I'll look into them a bit more today.