This is a simple little analog (CV) sync adapter for use with LSDJ and Nanoloop on a Nintendo Gameboy. The 3.5mm jack can be used as either an input or an output, selectable with the on board switch.
Due to varying sync standards, the Gameboy may or may not be able to sync with your gear. 2xAA created a helpful reference table. If you have data to add, please contact me.
This uses a GBA/GBC style link port. To use with an original brick Gameboy (DMG), you’ll need a good dual ended link cable. I’ve used this one and can recommend it: http://www.ebay.com/itm/400690419424