Debugging the MMU2 connection

If you encounter issues with the communication between the printer board and the MMU2, please enable

#define MMU2_DEBUG

in Configuration_adv.h and connect a serial terminal to the USB port of your printer board using Pronterface, Repetier Host, Octoprint, or Arduino IDE.

The following describes a startup sequence without issues

This is the debug output you should see in the serial terminal

Startup sequence

• Power on or reset
• Marlin bootscreen, MMU2 will do its init sequence: different LEDs lighting up, idler drum will move/home

• Marlin bugfix-2.0.x (or whatever version you are using)

• MMU <= reset

• MMU2 will do its init sequence again

• MMU => ‘start’

• MMU <= ‘S1’

• MMU => 103 (value depends on the MMU2 firmware version)

• MMU <= ‘S2’

• MMU => 212 (value depends on the MMU2 firmware version)

• MMU <= ‘M1’ (only if you enabled 12V mode in Configuration_adv.h)

• MMU => ok (only if you enabled 12V mode in Configuration_adv.h)

• _MMU <= ‘P0’

• _MMU => 0

• _MMU - ENABLED

## First tool change

When a tool change command like T0 is sent the first time, the following should happen

• MMU <= ‘T0’

• MMU2 will home the selector and load filament from the first lane to the extruder

• MMU => ‘ok’