mmu2s-clone

Update of the MMU2 firmware for ramps from : https://github.com/cskozlowski/mmu2/blob/master/doc/BOM.md

Project on https://www.thingiverse.com/thing:3910546

Now work with :

• MMU2S
• SKR mini or GT2560 board

TODO :

• describe new feature
• Wire schematic
• Marlin 2.0 configuration
• howto compile / use it