Prusa MMU2 (#12967)

Marlin/src/feature/prusa_MMU2/serial-protocol.md

@@ -0,0 +1,94 @@
+Startup sequence
+================
+
+When initialized, MMU sends
+
+- MMU => 'start\n'
+
+We follow with
+
+- MMU <= 'S1\n'
+- MMU => 'ok*Firmware version*\n'
+- MMU <= 'S2\n'
+- MMU => 'ok*Build number*\n'
+
+#if (12V_mode)
+
+- MMU <= 'M1\n'
+- MMU => 'ok\n'
+
+#endif
+
+- MMU <= 'P0\n'
+- MMU => '*FINDA status*\n'
+
+Now we are sure MMU is available and ready. If there was a timeout or other communication problem somewhere, printer will be killed.
+
+- *Firmware version* is an integer value, but we don't care about it
+- *Build number* is an integer value and has to be >=126, or =>132 if 12V mode is enabled
+- *FINDA status* is 1 if the is filament loaded to the extruder, 0 otherwise
+
+
+*Build number* is checked against the required value, if it does not match, printer is halted.
+
+
+
+Toolchange
+==========
+
+- MMU <= 'T*Filament index*\n'
+
+MMU sends
+
+- MMU => 'ok\n'
+
+as soon as the filament is fed down to the extruder. We follow with
+
+- MMU <= 'C0\n'
+
+MMU will feed a few more millimeters of filament for the extruder gears to grab.
+When done, the MMU sends
+
+- MMU => 'ok\n'
+
+We don't wait for a response here but immediately continue with the next gcode which should
+be one or more extruder moves to feed the filament into the hotend.
+
+
+FINDA status
+============
+
+- MMU <= 'P0\n'
+- MMU => '*FINDA status*\n'
+
+*FINDA status* is 1 if the is filament loaded to the extruder, 0 otherwise. This could be used as filament runout sensor if probed regularly.
+
+
+
+Load filament
+=============
+
+- MMU <= 'L*Filament index*\n'
+
+MMU will feed filament down to the extruder, when done
+
+- MMU => 'ok\n'
+
+
+Unload filament
+=============
+
+- MMU <= 'U0\n'
+
+MMU will retract current filament from the extruder, when done
+
+- MMU => 'ok\n'
+
+
+
+Eject filament
+==============
+
+- MMU <= 'E*Filament index*\n'
+- MMU => 'ok\n'
+