# Avoid errors if a secondary MCU is not connected **URL:** \ **Category:** General Discussion\ **Created:** [January 25, 2025, 3:09pm UTC](https://klipper.discourse.group/t/avoid-errors-if-a-secondary-mcu-is-not-connected/21618 "2025-01-25T15:09:15Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Escrich](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/escrich/32/4603_2.png) [@Escrich](https://klipper.discourse.group/u/Escrich)\ **Post date:** [January 25, 2025, 3:09pm UTC](https://klipper.discourse.group/t/avoid-errors-if-a-secondary-mcu-is-not-connected/21618/1 "2025-01-25T15:09:15Z")
### Basic Information: Printer Model: Custom designed Cuore 3D printer MCU / Printerboard: Octopus Host / SBC: Raspberry pi 5, including nvme disk unit klippy.log N/A Dear all in some of my machines I use a shaping detector based on a MCU, in some printers I use two simultaneously, one for each axis to be tested, then, if I have no the sensors connected, I need to have the line where I call the related macros commented, otherwise I’ll get an error trying to start without the sensors, at opposite, if need to use the sensors, I’ll need to uncomment the aforementioned lines in order to make them working, then my question is, is there any way to avoid this currently, will it be implemented in a nead future, does it exist any way to override or avoid this error with some code in a macro? ---
**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:** [January 25, 2025, 3:27pm UTC](https://klipper.discourse.group/t/avoid-errors-if-a-secondary-mcu-is-not-connected/21618/2 "2025-01-25T15:27:34Z")
Currently, Klipper requires all defined and used MCUs to be online when Klipper starts. AFAIK, there is nothing in the pipeline or planned to change this behavior. The best advice is to work with some [include statements](https://www.klipper3d.org/Config_Reference.html#include) and (un)comment as needed. ---
**Author:** ![Escrich](https://yyz2.discourse-cdn.com/free1/user_avatar/klipper.discourse.group/escrich/32/4603_2.png) [@Escrich](https://klipper.discourse.group/u/Escrich)\ **Post date:** [January 25, 2025, 6:21pm UTC](https://klipper.discourse.group/t/avoid-errors-if-a-secondary-mcu-is-not-connected/21618/3 "2025-01-25T18:21:58Z")
This is exactly what I currently do, but I’m looking for something better ---
**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/klipper/original/1X/64419bf2aac6639e6ef5cef200dcd456b0a01ac3.png) [@system](https://klipper.discourse.group/u/system)\ **Post date:** [March 26, 2025, 6:22pm UTC](https://klipper.discourse.group/t/avoid-errors-if-a-secondary-mcu-is-not-connected/21618/4 "2025-03-26T18:22:23Z")
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