Merlin 100 USB conversion - Fujitsu Leaf Spring 3rd gen \*Edit: It might be FLS 4th gen? It's for sure Fujitsu Leaf spring, but the leafs are integrated into the "stem plate" and the leafs press onto a 3 layer membrane. This is a keyboard out of an old Merlin 100 label maker that I converted to USB. One of the key requirements for this build was that I wanted to keep the vacuum fluorescent display working. After a lot of trial and error (and nearly totally bricking the VFD controller!) I figured out that the lable maker was sending ASCII characters through async serial at a break neck 300 bauds. Rest was figuring out how to make QMK output serial with each keypress (fairly straightforward with STM32, absolute nightmare with pro-micro I was initially using) and using absolutely every available pins on the bluepill to connect the original keyboard matrix up to it. Special thanks to Haata, who generously dumped the ROM from his Merlin 100 after I accidentally shorted and killed my EPROM.…