Klipper MCU: Unable to Connect: What's Wrong? Exploring the Issues Behind 'MCU: Unable to Connect'

[@steveu235]

I had that problem I had to format the sd card to the smaller size when formmating the sd card

[@minimal3dp]

I forgot to mention that the SD card used toflaah is oftern an issue. Thanks for pointing it out.

[@antisocial77]

how smaller? 4096?

[@edobatt1794]

I couldn't connect and I found that replacing "/dev/serial/by-id" with "/dev/serial/by-path" solved the problem

[@Willdabeast1138]

I didn't have any issue setting up one printer thanks to Minimal 3DP other videos but when I tried to set up two printer with two instances of Klipper I had some trouble. Hopefully this will help someone else having connection problems. It took me way to long to figure out but the problem I was having was I couldn't get more than one printer going at a time. One printer would connect in mainsail and the other wouldn't. I would swap usb around and power cycle then the other one would start working. I was getting "Printer is not ready. The klippy host software is attempting to connect. Please retry in a few moments." and the Klipper log show "Unable to open serial port: [Errno 11] Could not exclusively lock port /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0: [Errno 11] Resource temporarily unavailable" Well I guess raspberry pi cant auto address usb port or something (not 100% sure why, this is the first time I've touch a pi or ssh). Anyways if you look at your printer.cfg file under [mcu] serial: the default is "by-id" and probably looks like this /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0. You need to change it to "by-path" and it will look like this /dev/serial/by-path/platform-fd500000.pcie-pci-0000:01:00.0-usb-0:1.2:1.0-port0 depending what usb port you're using. To find the exact ports, open your terminal program of choice and ssh over to the pi then type in "ls /dev/serial/by-path/*" which will list the usb port you have printer plugged into. In my case it had two ports listed. I changed the printer.cfg file and bam hours of frustration over. I did have to change it twice because I guessed between the two listed ports wrong (I didn't which of the two listed port were what). But between that and Minimal 3DP videos I was set. Hopefully this will help save someone else some time.

[@minimal3dp]

Thanks for the explanation.

[@Doubius]

I hadn't updated the MCU location in my printer.cfg. That, and having a hard time flashing my board thru the RasPi SSH led me to use the OctoPrint plugin Firmware Updater with the downloaded .hex file compiled on the Pi. Thanks for this video! Helped me realize what I was doing wrong.

[@minimal3dp]

I'm glad you found the video helpful.

[@Jim_One-wl4ke]

What I had is klipper is attempting to start on klipper screen. before this it was Adc over range, max min temp so I plug both heaters & sensors in & also change the sensor type to generic. Reboot & that error was gone left with attempting to start, so search online n try make clean n do again. Still trying as from yesterday. Thanks for making this video i will watch several times again to see what I missed. Btw I m using BTT pi & SKR1.4 LPC1768. Thanks bro for sharing ❤

[@minimal3dp]

Glad you found this helpful. Happy to help.

[@Digitallifeconcepts]

Hi, thank you for this video. I am fighting with an Aquilla n32 with a Inovato Quadra MCU. And stuck at the dreaded MCU wont connect. Neither of the "/dev/serial/by-id" with "/dev/serial/by-path" return results the work. I have changed SD cards. reflashed the n32,, Reformatted the MCU to factory and started over again 6 times to be sure i got everthing done in order. but after a week....I need some help

[@thespacecowboy420]

if you have the LDO kit and are going right to USB you have an entry for the leviathan and one for the nighthawk in the config, both must be right. You may have to wait until more assembly is done before finalizing mainsail.

[@PenitentHollow]

I hope you can help me. I can get my printer running, and even starts a print, but half way through it shuts down with the message, "Can not update MCU mcu config as it is shutdown." I'm running an Ender 3 v2 off of a Sonic Pad connected to the BTT SKR Mini E3 V3. I have tried everything I can think of though I've only been using klipper for a short time. Any advice would be great.

[@minimal3dp]

Have you looked at the logs for both Klipper and moonraker? If you email them to me, I will take a Quick Look.

[@sambartling6787]

Mike, Is there a way to use STM32cube on a pie to update my x2 printers firmware file? I cannot get my laptop to connect to the printer to update it. it fails.

[@minimal3dp]

Can you use an SD to flash? Cube will probably have the same isse as your laptop.

[@sambartling6787]

@@minimal3dp so my rasp pi 4B can read it when plugged into it. So I was curious if there is a way to update the firmware on the x2 through the pi. I haven't tried the SD card route as I havent looked up that way.

[@minimal3dp]

@@sambartling6787 yes there is a way to do it via the pi. I believe that there are commands to do it. I am not sure of the commands but try searching for "Klipper make flash"

[@sambartling6787]

@minimal3dp I tried the SD card slot and it doesn't boot the firmware and write it. Do I have a bad mainboard?

[@Digitallifeconcepts]

Hi, thank you for this video. I am fighting with an Aquilla n32 with a Inovato Quadra MCU. And stuck at the dreaded MCU wont connect. Neither of the "/dev/serial/by-id" with "/dev/serial/by-path" return results the work. I have changed SD cards. reflashed the n32,, Reformatted the MCU to factory and started over again 6 times to be sure i got everthing done in order. but after a week....I need some help. when you paste in serial-by-id....I dont get that same data.

[@minimal3dp]

Have you tried a different USB cord?

[@minimal3dp]

Feel free to email me you board specifications and printer.cfg file. [e-mail]

[@Digitallifeconcepts]

​@@minimal3dp3 different usb and have more on order.

[@Digitallifeconcepts]

​@minimal3dp thank you I will.

[@robinpressl9731]

@@Digitallifeconcepts have you found a solution?

[@jonasowens27]

your the best man.i am new to klipper trying to set it up on sv03 with skr e3 v3 with h2 v2 extruder .man alot of things to go through.im setting a tablet up for touchscreen any advice on my setup

[@minimal3dp]

Sounds like a good plan. What tablet?

[@crooker2]

My main issue right now is: I have 2 printers. An Ender 3V2 and an Ender 3V3. When I run kiauh and install klipper and octoprint, plug both my printers in... it's not seeing 2 MCU's. It's only seeing one. I'm trying to get Klipper working on my V2 (with Mainsail), but for now, I want to keep the stock firmware on my V3 (Controlled by Octoprint) I have had each of them running individually... but I can't seem to get them both detected at the same time. Quite annoying.

[@minimal3dp]

Try plugging the printers in one at a time and checking the mcu.

[@Karmablock]

ls /dev/serial/by-id/*' still showing No such file or directory. I have been trying to get this to work since 11am it's now almost 8pm and still can't get this to work. I've followed your videos and advice and nothing. I've redone everything from the ground up several time and always have this error. No one knows why it doesn't work.

[@minimal3dp]

I am wondering if klipper made it onto the board. You might also want to try another cable. Feel free to email me at [e-mail] if you want to set up a zoom and we can take a look.

[@Therealgigachad70]

Have you solved the issue? I have the same issue

[@haven-hw2wl]

hello sir im have a prob with thin client wyse, i cant find a solution on how to connect my printer to wyse thin client. but i already install mainsail and klipper and see the usb path. im totaly new in 3d printing and exploring klipper with my ender 3

[@minimal3dp]

Have you updated the printer.cfg with the USB path you see?

[@haven-hw2wl]

Yes sir i already update it in printer.cfg and flash the firmware for the board, but it's just saying printer not ready and, firmwares restart error

[@terryterry1655]

in the printer.cfg...i just insert the MCU id to solve issue of printer not ready. Thx

[@Rasle500]

How do you open Klipper Firmware Config???

[@minimal3dp]

Go to the Klipper directory on your pi and type “make menuconfig”

[@Rasle500]

@@minimal3dp Thank you

[@Tn-yl3cm]

Thanks men i was about to scrap the hole projekt

[@minimal3dp]

hope you got it all running. Let me know if you have questions.

[@thebrelon]

Oh man..... Been fighting that for 3hours today when it was all fine yesterday! Came out of the blue on first power up today. Not solved yet, it's a tomorrow job.

[@minimal3dp]

I had that last week. I updated Klipper and things went blue. I had to reinstall Klipper on the board and everything worked.

[@thebrelon]

@@minimal3dp fixed it. I was not careful enough when copy-pasting and introduced a second [MCU] serial: /dev/..... In my generic-bigtreetech-manta-m8p-V2_0.cfg file..... Rookie mistake!

[@MsLuis735]

Klipper reports: STARTUP Printer is not ready The klippy host software is attempting to connect. Please retry in a few moments.

[@minimal3dp]

Check your cords and wifi connection.

[@kehoraerrios6881]

my only issue is this on going issue with the Sonic Pad always Webhook stop request or MCU shut down request not to sure but its been an ongoing issue with STM32f103. Even did a Debian 11 on the pad still same issue comunication error im at a real loss tryed at least a few dozen usb cords and even moving the printer to diffrent areas and special usb power blockers and all kinds of Who HAS. I think the pad or the motherboard on the printer is an issue now. More than likely its the dam pad that is defective.

[@minimal3dp]

Sorry to hear about your issues with the sonic pad. I don't have one so I can't be of much help.