# "mcu" unable to connect **URL:** \ **Category:** General Discussion\ **Created:** [July 25, 2023, 2:26pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634 "2023-07-25T14:26:52Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Peurif](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@Peurif](https://klipper.discourse.group/u/Peurif)\ **Post date:** [July 25, 2023, 2:26pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/1 "2023-07-25T14:26:52Z")
### Basic Information: Printer Model: RatRig Vcore 31 MCU / Printerboard: Octopus Pro + SHT42 `klippy.log` [klippy.log](https://klipper.discourse.group/uploads/short-url/sA5jvo0LedutGihdSna2ekGCD0H.log) (345.4 KB) _Fill out above information and_ **_in all cases attach your_ `klippy.log` _file_**. _Pasting your_ `printer.cfg` _is **not** needed_ _**Be sure to check our [Knowledge Base](https://klipper.discourse.group/t/about-the-knowledge-base-category-table-of-contents/6228) and in particular [this](https://klipper.discourse.group/t/how-to-trouble-shoot/6326) and [this](https://klipper.discourse.group/t/how-to-ask-for-help/6327) post**_ ### Describe your issue: ![Not MCU](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/4/497faae1d924af90a3414216eae8b8292783d907.png) ![LsUsb](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/a/a34af745f4db8dbcfb83913bc07b32f4897cac68.png) ![Extract Octopus Pro in RatOS](https://global.discourse-cdn.com/free1/uploads/klipper/original/2X/5/5045061911bfc40f01abbe1cbeabe52314b5ee74.png) Hi, I want to try to make the klipper configuration in 1 file, not in many as I have now. For this I decided to start from scratch, reinstalling RatOs… But the first one on the front, RatOs (a version of Mainsail with many Macros) does not find the MCU, when Rpi sees it via USB, and a few hours ago, Fluidd saw it… Does anyone know why this could be? … ---
**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:** [July 25, 2023, 4:09pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/2 "2023-07-25T16:09:01Z")
Use the command: ```auto ls /dev/serial/by-id/* ``` and replace the `serial: ...` with the correct output ---
**Author:** ![Peurif](https://avatars.discourse-cdn.com/v4/letter/p/c57346/32.png) [@Peurif](https://klipper.discourse.group/u/Peurif)\ **Post date:** [July 25, 2023, 6:33pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/3 "2023-07-25T18:33:21Z")
i have sended > ls /dev/serial/by-id/\* the console responds… > /dev/serial/by-id/usb-Klipper\_stm32f429xx\_3A0039000D50304738313820-if00 the correct line would be? > [mcu] > serial: /dev/usb-Klipper\_stm32f429xx\_3A0039000D50304738313820-if00 That “name” change would have been because the firmware it has installed is different from the one provided by RatRig. In the RatRig the name is changed… I suposse… ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [July 25, 2023, 7:21pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/4 "2023-07-25T19:21:17Z")
As it is described here: [https://www.klipper3d.org/Installation.html#configuring-klipper](https://www.klipper3d.org/Installation.html#configuring-klipper) it needs the full path. ---
**Author:** ![jakep\_82](https://avatars.discourse-cdn.com/v4/letter/j/ea666f/32.png) [@jakep\_82](https://klipper.discourse.group/u/jakep_82)\ **Post date:** [July 25, 2023, 7:44pm UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/5 "2023-07-25T19:44:42Z")
> [@Peurif](#): > > [mcu] > serial: /dev/usb-Klipper\_stm32f429xx\_3A0039000D50304738313820-if00 This is wrong. Just copy paste the exact console output from the command you ran. ---
**Author:** ![EddyMI3D](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/eddymi3d/32/1981_2.png) [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)\ **Post date:** [October 26, 2024, 5:51am UTC](https://klipper.discourse.group/t/mcu-unable-to-connect/9634/6 "2024-10-26T05:51:39Z")