Using the Micro Pro (32U4 processor) as a MIDI-to-USB device (MidiUSB.h library) I have no problem working with Windows 7 - all data transmitted & correct.
With the same setup into Windows XP (I have old synths I like to use which won’t work under Win7), & I get the transmission of two notes then nothing more.
Since my sequencer, synths, & any other programs work flawlessly with WinXP,
Is there a general incompatability with MidiUSB libraries or is it more likely to be the Micro Pro driver?
Hmmmm. I have not heard of this issue before. I can’t confidently state if the Pro Micro or the library is the issue here I am afraid.
It seems like the only piece of the puzzle that is changing is the computer you are using. If you tried a second Windows XP machine and/or try a different yet similar library, you may be able to figure out what the issue is.
Let us know what happens if you experiment.
I think I have resolved this issue - I am now convinced that which USB port I used made the difference. I believe a driver from another piece of software set to monitor that USB port, was causing a second access to the same USB channel in the computer’s data bus - CLASH! It is from an old Generator synth etc - so drivers fighting over the same data, like two dogs fighting over the same bone. Now after removing the other driver, all good! So that offending driver was trying to use the very same USB channel.
Fantastic, I am happy to hear that you have resolved the issue. I am glad it was a simple, yet cryptic problem.
Happy hacking.