This is a repository for MIDI hardware utility projects. I actually designed a whole family of MIDI Thru, Mergers and sync units from the most basic to the complex devices with merging capabilities, please see my store items and review Youtube video. https://www.youtube.com/watch?v=HIda10k1Uxs
It's targeted DIY community and available as PCBs or complete kits for purchase at Tindie: https://www.tindie.com/stores/deftaudio/