MBHP_DIN_IN_Module is a MIDI breakout board for the MBHP_CORE_STM32F4 module.
It consists of two MIDI IN/OUT pairs and MIDI Activity LEDs which are connected to monoflops.
The input socket J1 has to be connected to J11E of the MBHP_CORE_STM32F4 module. J1 of a second MBHP_MIDI_IO can be connected to J2 in order to get 4 MIDI INs/OUTs in total. More modules can't be chained (4 IN/OUT ports maximum).
This approach has the advantage, that the builder can decide by himself, if - and how many - MIDI IOs he wants to add to his MIDIbox.
Note that the MIDI activity indicators are only an optional feature. The circuit will also work without the circuit around the 74HC00 ICs (see schematic).