# Unable to connect to MCU

**URL:** <https://klipper.discourse.group/t/unable-to-connect-to-mcu/13094>\
**Category:** General Discussion\
**Created:** [January 13, 2024, 12:37pm UTC](https://klipper.discourse.group/t/unable-to-connect-to-mcu/13094 "2024-01-13T12:37:48Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![figugegu](https://avatars.discourse-cdn.com/v4/letter/f/47e85d/32.png) [@figugegu](https://klipper.discourse.group/u/figugegu)\
**Post date:** [January 13, 2024, 12:37pm UTC](https://klipper.discourse.group/t/unable-to-connect-to-mcu/13094/1 "2024-01-13T12:37:48Z")

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Hello everyone  
My Ender 3V2 has been running Klipper for a year now. And without any problems. Well, from one day to the next the PI can no longer connect to the board.  
I did all the updates, re-flashed the firmware from the board, tried other cables, other USB ports on the PI. Without success! I found various posts in the forum, unfortunately without success.

The Ender 3V2 is running with BTT SKR Mini E3 V3

Any ideas?

When I run ls /dev/, the “serial” is displayed, so there is a connection to the board.

> ls /dev/serial/by-id/

returns no such file or directory found.

> pi@mainsail:~ $ ls /dev/  
> autofs loop4 ram15 tty14 tty4 tty8 vcsu  
> block loop5 ram2 tty15 tty40 tty9 vcsu1  
> btrfs-control loop6 ram3 tty16 tty41 ttyACM0 vcsu2  
> bus loop7 ram4 tty17 tty42 ttyAMA0 vcsu3  
> cachefiles loop-control ram5 tty18 tty43 ttyprintk vcsu4  
> char mapper ram6 tty19 tty44 ttyS0 vcsu5  
> console media0 ram7 tty2 tty45 uhid vcsu6  
> cpu\_dma\_latency media1 ram8 tty20 tty46 uinput vga\_arbiter  
> cuse media2 ram9 tty21 tty47 urandom vhci  
> disk media3 random tty22 tty48 v4l vhost-net  
> dma\_heap mem rfkill tty23 tty49 vchiq vhost-vsock  
> fb0 mmcblk0 serial tty24 tty5 vcio video10  
> fd mmcblk0p1 serial0 tty25 tty50 vc-mem video11  
> full mmcblk0p2 serial1 tty26 tty51 vcs video12  
> fuse mqueue shm tty27 tty52 vcs1 video13  
> gpiochip0 net snd tty28 tty53 vcs2 video14  
> gpiochip1 null spidev0.0 tty29 tty54 vcs3 video15  
> gpiomem port spidev0.1 tty3 tty55 vcs4 video16  
> hwrng ppp stderr tty30 tty56 vcs5 video18  
> initctl ptmx stdin tty31 tty57 vcs6 video19  
> input pts stdout tty32 tty58 vcsa video20  
> kmsg ram0 tty tty33 tty59 vcsa1 video21  
> kvm ram1 tty0 tty34 tty6 vcsa2 video22  
> log ram10 tty1 tty35 tty60 vcsa3 video23  
> loop0 ram11 tty10 tty36 tty61 vcsa4 video31  
> loop1 ram12 tty11 tty37 tty62 vcsa5 watchdog  
> loop2 ram13 tty12 tty38 tty63 vcsa6 watchdog0  
> loop3 ram14 tty13 tty39 tty7 vcsm-cma zero

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<div class="post-metadata">

**Author:** ![linuxpaul](https://avatars.discourse-cdn.com/v4/letter/l/f9ae1b/32.png) [@linuxpaul](https://klipper.discourse.group/u/linuxpaul)\
**Post date:** [January 13, 2024, 3:49pm UTC](https://klipper.discourse.group/t/unable-to-connect-to-mcu/13094/2 "2024-01-13T15:49:31Z")

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Posts from other groups point to an OS bug. Have you already place a post to the guys who provide the OS image? Myself I also struggle with some other version depending conficts with my milling machine and I moved back to a buster image for the moment.

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/klipper/original/1X/64419bf2aac6639e6ef5cef200dcd456b0a01ac3.png) [@system](https://klipper.discourse.group/u/system)\
**Post date:** [March 13, 2024, 3:50pm UTC](https://klipper.discourse.group/t/unable-to-connect-to-mcu/13094/3 "2024-03-13T15:50:09Z")

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