3.1.1-RC5 firmware for Prusa i3 MK3

3.1.1-RC5 firmware for Prusa i3 MK3

Summary:

• Print reliability improved
• Test for swapped fans extended
• Firmware version messages shown on printer startup
• Bed temperature runaway
• Fail stats fixed
• Mode switching during print fixed
• Crash detection message added
• Improved displaying of status messages
• Filament change updated
• Serial communication improved
• Load filament beep
• Wizard fixes
• Modified unload filament sequence

Summary of previous releases can be found here:
https://www.prusa3d.com/drivers/

Detailed description of changes:

Print reliability improved

In previous firmware versions there were timing issues in some cases when CPU load was too high. This led to communication errors during USB prints (checksum mismatches, missing characters) and random motor kicks (layer shifts). Reason of high CPU load was linear advance feature and that's why this feature was temporarily removed and we are currently working on better solution.

Another improvement for print reliability is implementation of safe hard limits (jerk, feedrate, acceleration) which are different for normal and stealth mode and ensures that mechanical printer limits will never be exceeded.

hardlimit values for XY in "normal" mode:
jerk: 10 [mm/s]
feedrate: 200 [mm/s]
acceleration: 2500 [mm/s^2]

hardlimit values for XY in "stealth" mode:
jerk: 10 [mm/s]
feedrate: 172 [mm/s]
acceleration: 960 [mm/s^2]

Test for swapped fans extended

Selftest contains automatic test for detection if fans are swapped. In this test fan rotational speed is measured. Each fan has different rotational speed so it is possible detect swapped fans. However in some cases there were false swapped fans detections caused by variability in fan parameters. In current firmware version if automatic test detects swapped fans, there is another step where user checks which fan is actually enabled.

Fail stats fixed

Filament fails counter has been fixed.

Filament change updated (M600)

Filament change procedure (which is used in case that filament sensor detects end of filament) waits for user before unload starts. In current firmware version there is 10 minutes timeout. After this timeout hotend target temperature is set to zero. This prevents degradation of material in hot nozzle. M600 procedure was generally slightly updated to provide better guidance for user.

Serial communication improved

When printer was in blocking state (for example waiting for user interaction) and couldn't respond on serial line, Rx buffer became full which leaded later to undesired behavior. This occured typiccaly with Pronterface which sends requests for printer temperatures (M105) frequently. This has been fixed.

Wizard fixes

When running Wizard with erased eeprom memory some undesired behavior was observed (stealth mode was used during calibrations).
Also when running first layer calibration from wizard, there was case where live adjust Z value was not saved. These issues has been fixed.

Mode switching during print fixed

When switching from normal mode with crash detection enabled to stealth mode, there is message that informs user that in stealth mode, crash detection is disabled. This message paused print. In current firmware release, showing this message in non-blocking and has no influence on printing.