Hi sparkys,
I have designed a MIDI interface in Flex/Flash (AS3) for the purposes of storing and sending MIDI Program Change commands, with single channel presets as well as multiple channel presets. I am in the process of researching the components, etc. for this project, and I would appreciate some guidance.
From what I can tell, the STM32 is the way to go because I do want to connect both with a computer, and to multiplex several other MIDI controller devices I am designing to follow this current one. My design specifies that MIDI will return to the computer via USB.
The components I need for this interface are as follows :
56 buttons (backlit when selected, hopefully, or at least some indication)
1 slider (rheostat)
1 4x40 character blue LCD Display
4 red LEDs
For this, I am under the impression that I will need to following modules :
Core32
DIN
DOUT
Because this MIDI Controller is only one of a suite of devices I have designed, I am also considering the MBNet TK has alluded to on the uCAPPS site.
Any thoughts or suggestions would be appreciated. I’ve been poring through the 1200 page Mouser catalog, but my eyes glaze over after a period of time. 
Thanks,
Glennzone