[sdiy] Top Octave Modular

[Colin f]

> Nevermind..... looked closer at the MIDIbox info and found that the bits that
> control the I/O run at 5V.
> 
> -Ian

There's a difference between "5V tolerant" and "running at 5V".
5V tolerant pins can be driven to 5V as inputs, by virtue of having special protection diodes.
In output mode, they only drive to 3.3V-ish.
You need to be sure the devices you are driving have a high-level input threshold sufficiently below 3.3V to register the outputs correctly.

Cheers,
Colin f