Klipper won’t connect to my Creality 4.2.2 board — fails with error (-71)

LS3D · December 9, 2025, 10:47pm

Basic Information:

Printer Model: Ender 3 V2
MCU / Printerboard: STFM103 - V4.2.2
Host / SBC - x86 based mini-pc with Debian 12 - Klipper + Moonraker + Mainsail
klippy.log

Fill out above information and in all cases attach your klippy.log file (use zip to compress it, if too big). Pasting your printer.cfg is not needed
Be sure to check our “Knowledge Base” Category first. Most relevant items, e.g. error messages, are covered there

klippy (1).log (43.0 KB)

Describe your issue:

Hi all,

I’m trying to run Klipper on a Creality 4.2.2 board (Ender 3 V2). The firmware flashes fine, and the CH340 USB‑serial chip shows up in lsusb:

“Bus 001 Device 008: ID 1a86:7523 QinHeng Electronics CH340 serial converter”

But Klipper fails to connect. The log shows: “mcu ‘mcu’: Starting serial connect mcu ‘mcu’: Unable to open serial port: [Errno 5] could not open port /dev/ttyUSB0: Input/output error”

Earlier I also saw: “ch341-uart: probe of ttyUSB0 failed with error -71”

As I said earlier this is a fresh install of Debian Bookworm on an x86 based Mini-PC, I have used KIAUH to install Klipper, Mainsail, Crowsnest, and Moonraker. I would also get the “unable to connect to mcu” error in Mainsail.

Does anyone have any solutions to this? I have attached my log.

cardoc · December 10, 2025, 12:26am

Use the utility in KIAUH to find the id of the SERIAL device. USB is the conduit but connection with the MCU is serial.

My guess is your board didn’t actually flash. If that is the case KIAUH won’t find your MCU. Creality 4.2.2 and 4.2.7 boards are notoriously hard to flash.

Google [Creality 4.2.2 klipper] and you’ll get 100’s of hits starting with this:

LS3D · December 10, 2025, 8:19pm

I first flashed the stock creality firmware and then flashed it with firmware obtained thru ‘make menuconfig’ - and its giving me the same result. There is this repeated “-71” error, how does one fix that?

cardoc · December 10, 2025, 8:41pm

What did you put into printer.cfg for the MCU ID?
A new klippy.log would help.

LS3D · December 10, 2025, 8:46pm

klippy.log (27.0 KB)

cardoc · December 10, 2025, 10:27pm

Mainsail connects to Moonraker now?

If so go the the system tab and click on [DEVICES], highlight serial and hit refresh.

Does /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0 show up?

LS3D · December 11, 2025, 4:24pm

Yes, its always been showing up, I get the /dev/serial/by-id/ and the /by-path/, I just did a re-install of klipper only thru KIAUH and now this is the screen I get on Mainsail, I have attached a new log.

klippy.log (7.5 KB)

cardoc · December 11, 2025, 6:56pm

Makes no sense to me… I’d try a different cable. Next I would triple check the settings in makemenu then recompile klippy.bin and reflash.

Don’t forget filename has to be different than the one that flashed the current FW.

Are you 100% sure your board is a V4.2.2 with the STM32F103 chip?

github.com/Ripjaw582/Klipper-Config-Creality-4.2.2-Board-Ender-3

printer.cfg

main

# This file contains pin mappings for the stock 2020 Creality Ender 3
# Pro with the 32-bit Creality 4.2.2 board. To use this config, during
# "make menuconfig" select the STM32F103 with a "28KiB bootloader" and
# serial (on USART1 PA10/PA9) communication.

# It should be noted that newer variations of this printer shipping in
# 2022 may have GD32F103 chips installed and not STM32F103. You may
# have to inspect the mainboard to ascertain which one you have. If it
# is the GD32F103 then please select Disable SWD at startup in the
# "make menuconfig" along with the same settings for STM32F103.

# If you prefer a direct serial connection, in "make menuconfig"
# select "Enable extra low-level configuration options" and select
# serial (on USART3 PB11/PB10), which is broken out on the 10 pin IDC
# cable used for the LCD module as follows:
# 3: Tx, 4: Rx, 9: GND, 10: VCC

# Flash this firmware by copying "out/klipper.bin" to a SD card and
# turning on the printer with the card inserted. The firmware
# filename must end in ".bin" and must not match the last filename

This file has been truncated. show original

LS3D · December 11, 2025, 9:01pm

Yes it is, I got the printer to work though, I put tape on the 5v pad on a data cable so it wouldn’t interfere among some other stuff, thanks for helping though!

cardoc · December 11, 2025, 10:29pm

Please mark your last post as the solution.

Happy printing

system · January 11, 2026, 8:29am

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.

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Klipper won’t connect to my Creality 4.2.2 board — fails with error (-71)

Basic Information:

Describe your issue:

Hi all,

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