This topic pops up regulary, but I can only say: in distance to other people, I’m not willing to release a buggy solution.
MIDI-Nator: was affected by the EUSART bug as well, this has been confirmed by Robert. Meanwhile the silicon issue has been fixed by Microchip, and if you’ve luck, you will be able to purchase a working chip (rev5) and won’t receive an old stock part. But there are additional issues, e.g. instable SysEx transfers under Windows, which has been solved by commercial companies by developing their own MIDI driver. Such drivers are protected, so that it isn’t possible to adapt the PIC firmware.
For my own interest I tested the firmware with a shiny new PIC18F4550 rev.5 under Mac OS today. Unfortunately it doesn’t work better as under Windows - in distance: just send some MIDI notes, thereafter a SysEx string - this will hang up the MIDI Out port (to USB experts: the OUT endpoint doesn’t receive any message anymore, BDn_STAT_UOWN is permanently set, no USB error is reported). Reconnect the interface, start with some SysEx messages: works. Send some notes: no MIDI out data anymore! MIDI In port is working better, but not perfectly (data loss on higher data rates)
Thereafter I tried Mac OS with Cypress based MBHP_USB instead: works perfectly! Even better than under Windows (multiclient capability! :-))
Thereafter I tried Robert’s MIDI-nator firmware: same effect as with MBHP_USB_PIC
Thereafter I searched in the internet for other firmwares and found Synthex’s firmware for the Megadrum project: same effect as with MBHP_USB_PIC
Frustrating!
RS232 solution: yes, some guys already tried this and know how to set it up - google for “ftdi usb midi”