When you use drivers that are already opto-isolated, then it's sensible to use a breakout board which doesn't have opto-isolated outputs, since as you say there's just no point doing it twice. In fact, since the drivers are isolated it's perfectly safe to connect them directly to the port and not use a breakout board, however you would still need to make an isolated circuit for the inputs, and it sometimes doesn't work if the port voltage is too low, so it's generally not worth it except for testing.

Quote Originally Posted by hbx View Post
Thanks! Do the boards somehow increase the number of inputs available? Perhaps by multiplexing?
Unfortunately not.