Had a bit of a nightmare with the timing of the outgoing commands, i managed to get single bits to be the correct length (440us), but the timing changed when sending commands with multiple consecutive highs or lows. It turns out opto-isolators are pretty slow and building a suitable level translator with output enable uses too many components (in the sizes i have) to fit on the D1 mini proto board, so i'm swapping the interface circuite to use a single 74lvc1t45 instead. I'll update the schematics and code sometime this week.