# 'mcu': Unable to open serial port **URL:** \ **Category:** General Discussion\ **Created:** [May 17, 2023, 6:42pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456 "2023-05-17T18:42:18Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 6:42pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/1 "2023-05-17T18:42:18Z")
### Basic Information: Printer Model: Sapphire Plus MCU / Printerboard: Octopus Pro `klippy.log` [klippy (5).log](https://klipper.discourse.group/uploads/short-url/3GJJLhA3MlrJV8dpkoA1LppjTXj.log) (468.3 KB) ### Describe your issue: … cannot find MCU. i try to follow a guide from Sineos here _ender-3-v2-linux-machine-no-mcu-found/4635/17_ but i don’t get any info from this command: _sudo systemctl list-units | grep brltty_ this is my sudo dmesg report [report sudo dmesg .txt](https://klipper.discourse.group/uploads/short-url/eiEPGfSxKD0v5abHj62h9WPHzEe.txt) (31.4 KB) please help me ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 6:56pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/2 "2023-05-17T18:56:51Z")
```auto [7.526943] cdc_acm 1-1.1:1.0: ttyACM0: USB ACM device [7.559907] usbcore: registered new interface driver cdc_acm [7.559944] cdc_acm: USB Abstract Control Model driver for USB modems and ISDN adapters ``` Likely the modemanager is spoiling your fun. See [Other Single Board Computers (SBC) apart from Raspberry Pis](https://klipper.discourse.group/t/other-single-board-computers-sbc-apart-from-raspberry-pis/6323#potential-pitfalls-4) ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 6:57pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/3 "2023-05-17T18:57:42Z")
sorry, i don’t understand. I have only a usb camera connected ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 6:58pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/4 "2023-05-17T18:58:22Z")
connected to my raspberry pi4 ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:01pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/5 "2023-05-17T19:01:04Z")
> [@Other Single Board Computers (SBC) apart from Raspberry Pis](https://klipper.discourse.group/t/other-single-board-computers-sbc-apart-from-raspberry-pis/6323/1): > > Some distributions install services that might interfere with Klipper. Most noteworthy are > > - ModemManager > - BRLTTY > > ```auto > # List all brltty services (replace with "modemmanger" to check this) > sudo systemctl list-units | grep brltty > # For each item in the result list of the above command run > sudo systemctl mask brltty.path > sudo systemctl stop brltty.path > # "brltty.path" is only an example. Replace it with the first command's output > > ``` Just follow this with modemmanger instead of brltty. It is a system service and has nothing to do with what you have connected. ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:01pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/6 "2023-05-17T19:01:27Z")
i tried sudo systemctl list-units | grep modemmanger but didn’t get any reply ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:03pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/7 "2023-05-17T19:03:54Z")
Hmm, acc to your dmesg, it is active. Try `dpkg -l | grep modem` ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:04pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/8 "2023-05-17T19:04:25Z")
> [@Sineos](#): > > dpkg -l | grep modem got this: pi@printer:~ $ dpkg -l | grep modem ii libmm-glib0:arm64 1.14.12-0.2 arm64 D-Bus service for managing modems - shared libraries ii modemmanager 1.14.12-0.2 arm64 D-Bus service for managing modems pi@printer:~ $ ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:05pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/9 "2023-05-17T19:05:48Z")
run: `sudo apt remove modemmanager` then reboot ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:07pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/10 "2023-05-17T19:07:52Z")
i did but still have the problem ☹ ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:12pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/11 "2023-05-17T19:12:13Z")
What is the output of `ls /dev/serial/by-id/*` Attach a new dmesg after replugging the board and a new klippy.log ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:13pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/12 "2023-05-17T19:13:09Z")
pi@printer:~ $ ls /dev/serial/by-id/\* ls: cannot access ‘/dev/serial/by-id/\*’: No such file or directory ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:15pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/13 "2023-05-17T19:15:17Z")
Reflash your board, paying extra attention to the correct `make menuconfig` options. Also check [Debian Bullseye Bug causing Klipper to no longer find the printer board - #5 by Sineos](https://klipper.discourse.group/t/debian-bullseye-bug-causing-klipper-to-no-longer-find-the-printer-board/8231/5) ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:15pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/14 "2023-05-17T19:15:42Z")
so only the board not the raspberry? ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:16pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/15 "2023-05-17T19:16:46Z")
Yes, only the board is needed ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:19pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/16 "2023-05-17T19:19:46Z")
i’m also doing the steps in your linked guide ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 17, 2023, 7:22pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/17 "2023-05-17T19:22:29Z")
It’s working!!! you made my day man! Many thanks!! do you still think i ned to reflash the board? ---
**Author:** ![Sineos](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/sineos/32/18_2.png) [@Sineos](https://klipper.discourse.group/u/Sineos)\ **Post date:** [May 17, 2023, 7:25pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/18 "2023-05-17T19:25:04Z")
Nope, if it is working, you are good to go. Have fun ---
**Author:** ![Morf90](https://avatars.discourse-cdn.com/v4/letter/m/e9a140/32.png) [@Morf90](https://klipper.discourse.group/u/Morf90)\ **Post date:** [May 18, 2023, 2:55pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/19 "2023-05-18T14:55:35Z")
Hi, I have another problem. It started yesterday little before the mcu problem. From Octoeverywhere and telegram bot i can’t get webcame anymore. I get no signal, but from a pc connected to the same wifi, it works. I am thinking something is not going well over all, what can it be? also now octoeverywhere works very badly after i send a print and when the print starts, it cannot connect to it anymore ---
**Author:** ![Ebro](https://avatars.discourse-cdn.com/v4/letter/e/9de0a6/32.png) [@Ebro](https://klipper.discourse.group/u/Ebro)\ **Post date:** [June 22, 2023, 7:31pm UTC](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456/20 "2023-06-22T19:31:31Z")
@Sineos, i’m lost and tryed a lot of things. I don’t know what i’m doing wrong… I shared my klippy.log file. [klippy (18).log](https://klipper.discourse.group/uploads/short-url/jbC7sTWDfeRLNzpteFuGlhU754h.log) (36.4 KB) [Next page](https://klipper.discourse.group/t/mcu-unable-to-open-serial-port/8456.md?page=2)