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 filament is 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 G-code 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'