Specs:

4x MIDI IN and 4x MIDI Out with USB2.0

The Software/Firmware is from ploytec and used in many commercial products.

PCB and Preprogrammed chip is available from me - send me a Email (15Euro plus shipping 6.60Euro)

(The costs what I paid for) - Not commercial sale.

BOM:

Partlist

https://docs.google.com/spreadsheets/d/1u6wgABhqt0vknTZJFNVShALNdmQvRK_okAad-lOCuyc/edit#gid=0

Addional parts which are not in the above BOM:

When you want the plastic/ABS case, order this 3 parts from TME.eu

Case:  G17081UBK Gehäuse:standardmäßig 19";1U;schwarz;Mat.Geh:ABS;Y:203mm

USB adapter:

CP30111 Adapter;USB A Buchse-Hinterteil,USB B Buchse-Vorderteil;FT ROHS Hersteller: CLIFF 

USB cable for inside: 

CAB-USBAB/0.19 Kabel;USB 2.0;USB A-Stecker,USB