All design credit to: Charles Mangin of option8 and shared here under open source hardware

Original Github page: https://github.com/option8/RetroConnector/tree/master/IIc-USB

Required Materials:

• Teensy ++ 2.0 - https://www.aliexpress.com/item/32559849517.html?spm=a2g0o.productlist.0.0.30522a85DaStlh&algo_pvid=500eaaf0-271a-4f4f-987c-272ebea69980&algo_expid=500eaaf0-271a-4f4f-987c-272ebea69980-1&btsid=0bb0624316156615877137420eea5f&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

• Male header pins - https://www.mouser.ca/ProductDetail/TE-Connectivity/2-826646-0?qs=sGAEpiMZZMvlX3nhDDO4AF9ulCqrHfKqye%2FbzqB9qOQ%3D

• female headers - https://www.mouser.ca/ProductDetail/855-M20-7822046

• box header (34-pins for //c, 26-pins for //e) - https://www.mouser.ca/ProductDetail/571-5103308-7

Software:

• RetroConnector firmware https://github.com/option8/retroconnector
• Arduino software http://arduino.cc/en/Main/Software
• teensyduino library http://www.pjrc.com/teensy/td_download.html
• keypad.h library http://playground.arduino.cc/Code/Keypad