6.5.1 Firmware for Prusa CORE One L

Summary

• Prusa CORE One L support
• Mains-powered AC bed
• Bed fan for faster chamber heat-up
• Automatic vent opening/closing
• Redesigned error screens (BSOD/RSOD)
• Reworked filament sensor selftest
• Experimental “Fast draw” mode
• Fixed RSOD when using too little filament in MMU prints
• Allow nozzles smaller than 0.2 mm
• Allow aborting on missing sheet
• Allow continuing a single selftest
• “Shipping reset” factory reset preset
• Small UBL code refactoring #4733

This release introduces support for the new Prusa CORE One L and its unique features, including a mains-powered AC bed and automatic chamber vents. It also features a redesign of the error screens (BSOD/RSOD) and several quality-of-life improvements.

Add support for the Prusa CORE One L printer

A new printer has joined our family! This firmware adds full support for the Prusa CORE One L and its unique hardware, including the new features detailed below.

Mains-powered AC bed (C1L)

The CORE One L introduces a new AC mains-powered (120–230 V) heatbed system. This enables significantly faster heat-up times but also requires additional safety measures implemented in the firmware. The bed runs its own firmware on a dedicated processor and is the first device to communicate via the new Cyphal/CAN-based Prusa Universal Bus.

Bed fans for faster chamber heat-up (C1L)

Similar to the CORE One, the CORE One L uses the heatbed to warm up the print chamber. To speed up this process, in addition to a more powerful heatbed, we’ve added two small fans beneath the bed that circulate air inside the chamber. This improves heat distribution and allows the chamber air to absorb heat more effectively from both the top and bottom sides of the heatbed.

Automatic vent opening/closing (C1L)

The CORE One L uses a simple mechanism on the print head to automatically open and close the chamber vents. This eliminates the manual user prompts required on the non-L version.

Redesigned BSOD/RSOD

The error screens have been completely redesigned to provide a calmer, more user-friendly experience when things go wrong. The layout has been updated, and the “Blue Screen of Death”*is now the “Black Screen of Death” — still keeping the familiar BSOD acronym.

Reworked filament sensor selftest

The internal logic of the filament sensor selftest has been reworked:

• The procedure now tests the side filament sensors on all relevant printers (this was done only on the XL).
• During calibration, the printer now moves the filament up and down to gather more robust data about the “inserted” state.
• The selftest is now available on the Prusa Mini (optionally, for users who bought the sensor accessory).

Experimental “Fast draw” mode

A new “Fast draw” option in Experimental Settings significantly improves display response speed. This is an experimental feature and minor visual artifacts may occur.

Fixed RSOD when using too little filament in MMU prints

Fixed a Red Screen of Death (RSOD) that occurred in multimaterial prints using very small amounts of a single filament (e.g., < 0.3 g).

Allow nozzles smaller than 0.2 mm

It is now possible to set the nozzle diameter to 0.1 and 0.15 mm in the Hardware menu. However, using such small nozzles is only recommended for advanced users, because they lack official profiles, increase print times, and have a higher risk of clogging and layer adhesion issues.

Allow aborting on missing sheet

The “STEEL SHEET NOT DETECTED” (XX109) error now includes an “Abort” option that aborts the print, in addition to “Continue” option.

Allow continuing a single selftest

After running an individual selftest from the Calibrations & Tests menu, the “Continue running Calibrations & Tests?” prompt now includes additional options. You can now choose to:
• Continue – run only the next selftest and then be prompted again, or
• All – continue running all remaining selftests automatically.
Previously, only the Continue option was available, which always continued all remaining selftests.

“Shipping reset” factory reset preset

We are now shipping assembled CORE One L printers pre-calibrated from the factory. To support this, a new “Shipping Reset” option has been added to the Factory Reset menu. This reset type keeps the hardware configuration and calibration data, while clearing all other settings.

Release notes:

https://github.com/prusa3d/Prusa-Firmware-Buddy/releases/tag/v6.5.1