Allow for multiple virtual MIDI cables (ports)

[ab5tract]

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The class compliant USB MIDI spec allows for 16 separate MIDI "virtual cables" (their terminology). This library appears to hardcode all transmissions to a single port.

[snodecoder]

16 virtual cables can only be used if a Teensy board is used. According to the datasheet s the Leonardo / Pro Micro boards have 6 configurable USB endpoints, so besides the 2 endpoints in use for Serial via USB, it should be possible to configure it with a total of 4 virtual cables, right?

Does anyone know what needs te be changed to allow for multiple virtual cables? I would like to help in adding this functionality, but I don't know where to begin ;)

[lathoub]

https://github.com/lathoub/Arduino-USBMIDI implements cables (and uses this library to implement the underlying USB calls). See example https://github.com/lathoub/Arduino-USBMIDI/tree/master/examples/CableNumber (specific cable nr) and https://github.com/lathoub/Arduino-USBMIDI/blob/master/examples/SysEx_Teensy4.1/SysEx_Teensy4.1.ino (multiple cables)