# Ender 3 V2 - MCU cannot be found

**URL:** <https://klipper.discourse.group/t/ender-3-v2-mcu-cannot-be-found/9451>\
**Category:** General Discussion\
**Created:** [July 14, 2023, 6:16pm UTC](https://klipper.discourse.group/t/ender-3-v2-mcu-cannot-be-found/9451 "2023-07-14T18:16:18Z")\
**Posts on this page:** 1\
**Showing post:** 5

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**Author:** ![Rbk](https://avatars.discourse-cdn.com/v4/letter/r/c57346/32.png) [@Rbk](https://klipper.discourse.group/u/Rbk)\
**Post date:** [July 17, 2023, 7:21am UTC](https://klipper.discourse.group/t/ender-3-v2-mcu-cannot-be-found/9451/5 "2023-07-17T07:21:54Z")

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Okay i have repeated the process.

The output of

> apt-cache policy udev

looks like this:

> udev:  
> Installed: 252.5-2~bpo11+1  
> Candidate: 252.5-2~bpo11+1  
> Version table:  
> \*\*\* 252.5-2~bpo11+1 100  
> 100 [Index of /debian](http://ftp.debian.org/debian) bullseye-backports/main armhf Packages  
> 100 /var/lib/dpkg/status  
> 247.3-7+rpi1+deb11u2 500  
> 500 [Index of /raspbian](http://raspbian.raspberrypi.org/raspbian) bullseye/main armhf Packages

Unfortunately following command still fails

> [@Debian Bullseye Bug causing Klipper to no longer find the printer board](https://klipper.discourse.group/t/debian-bullseye-bug-causing-klipper-to-no-longer-find-the-printer-board/8231/1):
>
> `ls /dev/serial/by-id/*`

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