I'm looking at creating a "specialized" MIDI over USB device for a project I'm working on and my requirements have gone beyond that of the Arduino/Pi/etc, due to limited I/O. I am very much a beginner in the world of MIDI, microcontrollers, etc. and would appreciate a jump-off point to get started.
For my project I need a MIDI Receive box that transmits the signal over USB, but I need it to be able to receive from 16 separate input devices. The Arduino Mega and Teensy 3.5/6 have the most UARTs to support this (I've decided against software serial options due to limitations), but the Teensy still only has 6 UART channels. I've come to the conclusion that building my own box would end up working best to allow me to accomplish what I need while avoiding what I don't.
I've found some UART chips from different manufacturers such as Exar and NXP that have 8 channels and also specify that they are built for PCI/PCIe applications, while the ones under the USB category list 2-4 channels. Would that mean I need to hook these 8-channels up to some sort of USB-PCIe adapter? And is it possible to combine two of these to obtain those 16 channels I mentioned? How would I get these to talk to my computer over USB? I read about using a FPGA; would this be the most straight-forward/easiest/most versatile option? Is there also some completely different approach to this which would be better suited?