Unable to Update MK3 Firmware from 3.13.1 to 3.14.1 – Port Timeout Issue  

Unable to Update MK3 Firmware from 3.13.1 to 3.14.1 – Port Timeout Issue

Hi everyone,

I'm having trouble updating the firmware on my MK3 from version 3.13.1 to 3.14.1. Despite multiple attempts using different methods, I keep getting the same error related to the COM port.

Here’s the log from my latest attempt:

avrdude-slic3r -v -p atmega2560 -c wiring -P COM3 -b 115200 -D -U flash:w:0:C:\Users\flemm\Downloads\prusa3d_fw_3_14_1_MK3\prusa3d_fw_3_14_1_MK3\MK3_FW_3.14.1_MULTILANG.hex:i

avrdude-slic3r: Version 6.3-20160220-prusa3d, compiled on Sep 12 2025 at 14:49:38 Copyright (c) 2000-2005 Brian Dean,  http://www.bdmicro.com/  Copyright (c) 2007-2014 Joerg Wunsch

Using Port : COM3 Using Programmer : wiring Overriding Baud Rate : 115200avrdude-slic3r: stk500v2_recv(): timeoutavrdude-slic3r: stk500v2_getsync(): timeout communicating with programmeravrdude-slic3r: Could not open port: COM3

avrdude-slic3r done. Thank you.

What I've tried so far:

• Multiple USB cables
• Multiple computers (Windows 10, Windows 11, Ubuntu, Raspberry Pi)
• Flashing via:
  • PrusaSlicer
  • Command line avrdude
  • OctoPrint
• Resetting the printer to factory defaults
• Power cycling or resetting the printer just before flashing
• Running programs as Administrator (Windows) or root (Linux)
• Verified that the port is is correct and works with OctoPrint on the Pi

Still getting the same error every time.

Does anyone have any suggestions or ideas on what else I can try?