I was having a fiddle round the other day with Processor Expert - found it quite easy to configure the UART to the 31250 bps that you need. (Think that was an HCS08 part - I've got those and Kinetis on the go at the moment, but Kinetis would be no harder with PEx.)
Biggest challenge is building the state machine to process MIDI input, but you should be able to adapt pretty well any C code that does that, just need to replace the UART bits with what PEx spits out.
If you'd asked in a year's time, I might have been able to share, but my MIDI project is a fair way down the queue at the moment :smileywink:
Just remember that, hardware-wise, you're using a current loop on the input (via an optocoupler) rather than just coming straight into the UART RXD, and that you need to buffer your output.
