Subject: Ender 5 Pro (4.2.7) - Stuck in "Disconnect" Loop / Firmware won't flash | 3D Printing | Page 1

cobalt apex May 14, 2026, 1:08 PM

#

Hey everyone, I'm at my wits' end trying to flash Klipper onto my Ender 5 Pro with the v4.2.7 Creality board. I’m using a Windows machine to prep everything, but I cannot get the board to "swallow" the firmware.

The Problem:

The printer screen is blank/blue (as expected), but the .bin file on the SD card never changes to .CUR.

Klipper/Mainsail just stays on "Printer is not ready" or a disconnect loop.

What I have tried so far:

SD Cards: Used an 8GB card, even tried partitioning it down to 2GB to help the bootloader.

Formatting: Formatted to FAT32 with a 4096 cluster size via Windows.

Naming: Tried multiple unique names (klipper.bin, a.bin, update1.bin, etc.) to avoid the filename-repeat bug.

Firmware Build: Compiled with the standard 4.2.7 settings (STM32F103, 28KiB bootloader, serial on USART1). Even tried the "Disable SWD at startup" option.

Hardware: Tried flashing with the USB cable unplugged to prevent back-powering issues.

Current Status:
The board just won't flash. Is it possible the bootloader is locked/bricked, or is there a "magic" SD card brand these boards require? Any advice before I give up and buy an SKR Mini E3?

hot cedarBOT May 14, 2026, 3:09 PM

#

This post has been closed due to inactivity.

This post has been inactive for over 1 hour and so has been closed. To reopen this post simply send another message.

cobalt apex May 14, 2026, 6:13 PM

#

bruh

median ridge May 14, 2026, 7:32 PM

#

cobalt apex Hey everyone, I'm at my wits' end trying to flash Klipper onto my Ender 5 Pro wi...

tried firmware.bin as the file name? sometimes is new name, sometimes its that exactly, and checked the output or ls /dev/serial/by-id?

#

my guess is it did flash, you just havent updated the MCU connection line

cobalt apex May 14, 2026, 7:39 PM

#

median ridge my guess is it did flash, you just havent updated the MCU connection line

lemme try that. honestly im not even sure what i have or have not tried at this point. i made attempts all day trying to make it work

#

yesterday

#

@median ridge one thing that worries me is the .bin file after i tried to flash when i chekc it with my pc it never changes to .cur or disapeers in any sort of way from the microsd card

median ridge May 14, 2026, 7:42 PM

#

from memory only some boards change to .cur, if the screen went off id think it flashed alright, its the connection next

cobalt apex May 14, 2026, 7:42 PM

#

aight lemme fire em up

#

@median ridge seems like i already did that and i just get printer is not ready until it throws an error becasue its not really responding.

median ridge May 14, 2026, 7:50 PM

#

and the ls /dev/serial/by-id?

cobalt apex May 14, 2026, 7:51 PM

#

it does give me a return

median ridge May 14, 2026, 7:52 PM

#

and you updated the config MCU section with it?

cobalt apex May 14, 2026, 7:52 PM

#

yep.

#

to my knowledge rthe ls /dev/serial/by-id allows for communicating with the usb controller but that does not confirm if the board actually got successfully flashed

median ridge May 14, 2026, 7:54 PM

#

to me if the screen went off it flashed, if its connected with the ls it can see it, trying to remember, there was some brail reader that blocked connections like that, some brltty?

cobalt apex May 14, 2026, 8:07 PM

#

Brail reader?

#

That i havent heard or read about

median ridge May 14, 2026, 8:08 PM

#

try a sudo apt-get remove brltty

#

just in case

#

comes preinstalled on some linux distros

#

past that you copy the whole string from the ls?

cobalt apex May 14, 2026, 8:15 PM

#

ls /dev/serial/by-id

like the thing it returns when i write this?
ls /dev/serial/by-id
yeh. the entire thing

#

Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package 'brltty' is not installed, so not removed
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

median ridge May 14, 2026, 8:20 PM

#

to confirm, in config it looks like

serial: /dev/serial/by-id/usb-xxxxxx```

cobalt apex May 14, 2026, 8:21 PM

#

[include mainsail.cfg]

[mcu]
serial: serial: /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0

#

omg

#

lemme try changing that

median ridge May 14, 2026, 8:23 PM

#

supprised that didnt throw a config error tbh

cobalt apex May 14, 2026, 8:24 PM

#

i still get an error

#

#

median ridge May 14, 2026, 8:33 PM

#

my only real last though is somehow the firmware was made wrong? any instructions that sounded wierd?

cobalt apex May 14, 2026, 8:35 PM

#

im not really sure tbh.
i just did the usual
make config thing
then select the approbiate stuff like stm 32
and the serial thing and etc
ive tried a couple times starting over making the .bin
i will say the bin is made on the pi itself.
then i copy it over to the micro sdcard

hot cedarBOT May 14, 2026, 10:39 PM

#

This post has been closed due to inactivity.

This post has been inactive for over 1 hour and so has been closed. To reopen this post simply send another message.

cobalt apex May 14, 2026, 11:38 PM

#

ive already purchased a new board. the btt skr mini something

cobalt apex May 15, 2026, 12:52 AM

#

@median ridge thanks for the help though

#Subject: Ender 5 Pro (4.2.7) - Stuck in "Disconnect" Loop / Firmware won't flash