I just introduced a MIDI interface board that is compatible with my NB1A, NB1 and ZB1 boards. The board features a MIDI input, output and four two-pole filters (for waveform smoothing). I have also added a transistor to disable MIDI input on bootup. The board works with the Arduino MIDI 3.0 library.
The schematic, BOM, assembly documentation and usage hints are in the datasheet at http://tinyurl.com/3lrxtp9
(* jcl *)