No MCU found! BTT SKR mini e3 V3

[jordibc]

Basic Information:

Printer Model: ENDER 3
MCU / Printerboard: BTT SKR mini e3 v3
Host / SBC
klippy.log

Fill out above information and in all cases attach your klippy.log file (use zip to compress it, if too big). Pasting your printer.cfg is not needed
Be sure to check our “Knowledge Base” Category first. Most relevant items, e.g. error messages, are covered there

Describe your issue:

I’ve installed Klipper several times, tried different cables, and different SD cards, but the problem remains unsolved. I’ve read several posts but can’t find a solution. I don’t know what else to do. I’d appreciate some help. Thank you very much.
klippy.log (25.5 KB)

…

[jordibc]

sudo dmesg.txt (35.4 KB)

[EddyMI3D]

Hello @jordibc !

As long you don’t change this:

[mcu]
serial = /dev/serial/by-id/<your-mcu-id>

it won’t work.

Have you tried this:

ls /dev/serial/by-id/*

as it is described in the docs?

[jordibc]

Yes but it doesn’t work:

@enderjordi:~ $ ls /dev/serial/by-id/*
ls: cannot access ‘/dev/serial/by-id/*’: No such file or directory

[EddyMI3D]

1. Do you have a proper connection from the Klipper host to the printer? Some USB cables don’t transport data.
2. Have you flashed the correct firmware to the printer?

[jordibc]

Yes, i have a usb for data transmission and i have flashed de correct configuration ( 3 times).

[mykepredko]

How do you know you’ve flashed the board correctly?

If there’s any doubt, I recommend that you turn on the STATUS LED when you create your image using make menuconfig. For the SKR Mini E3 V3 it’s pin PD8.

If it turns on (and off when you flash it again with the pin removed) then you know that you’re flashing the board correctly.

[jordibc]

I know because the firmware.bin change to firmware cur. Anyway i will try your method. Thank you (if you can gave me some more indications it will help me a lot hehe)

[Sineos]

@jordibc

I know because the firmware.bin change to firmware cur

There have been reports that this is not necessarily the case.
Despite this, your dmesg log does not contain any traces of a printer board flashed with Klipper, which also supports the notion that the board may not be correctly flashed.

For potential issues during the flashing process, also see Issues flashing the printer board
Using various SD cards smaller than 8GB is always a worthwhile first step.

[3dcoded]

@jordibc ,

How do you know your USB cable supports data? I had a similar issue in the past with an SKR Pico, and the culprit ended up being the fact that my “data” cable wasn’t actually a data cable.

The SKR Pico uses USB-C, so it was easy for me to plug my phone into my computer through various USB-C cables to make sure the cable supported data. The SKR Mini uses micro-USB, so it might be harder to find a device to test on.

SKR Pico not showing in lsusb

I was using mostly USB-C charging cables that had data support. At least two of the four I ended up trying have worked before on my FYSETC Portable Input Shaper. That is strange…it might be the USB-C dongle I use on my Mac. I sometimes have to switch which USB port I plug stuff into. Time to get a new dongle! Here are the four cables I tried [IMG_0729] From the left to right, I tested if each cable works with the SKR and my iPhone, plugged into a PC. By “works”, I mean it shows up as a U…

[mykepredko]

@jordibc

I know because the firmware.bin change to firmware cur.

Please note the comment @Sineos made on the issue.

I’m not sure that there are problems with the bootloader updating the firmware as I suspect that people are not building their Klipper firmware correctly.

Can you confirm that you have configured your build as BTT recommends in:

firmware/V3.0/Klipper/README.md

When I just did it on the latest Klipper build it looks like:

and, when you are turning on the STATUS LED (as explained above) it will be:

Don’t forget the bootloader offset - if you leave it as zero, the addresses put into the code will assume that the firmware is executing at the base address of the MCU (and not above the bootloader as it should) and will not execute properly.

[jordibc]

Thank you for your response.

I have tried as you describe, it seems that is flashing the board. Maybe the problem is the micro-USB cable or the micro-USB port of the board (it’s a second hand board). I will try the USART comunication.

Here the configuration and a video flashing the SKR mini

Video de WhatsApp 2025-04-05 a las 11.04.51_f9052781.zip (2.7 MB)

[mykepredko]

Your video looks good - I can see the STATUS LED lighting.

Now, you haven’t listed your “Host / SBC” as requested when you did the original post.

What are you using? A Raspberry Pi, a Linux/Mint laptop?

[jordibc]

A Raspberry Pi, configured with Raspbery pi Imager. I’ve already tried with the SO with klipper and mainsail preinstaled and without it (with raspberry pi OS lite 32-bit debian bullseye, Raspberry pi OS lite 32-bit debian bookworm and raspberry pi OS lite 64-bit) with the same result.

[jordibc]

Finally it’s working with USART comunication.

Here the connections if can help someone with my problem. It seems that te USB port is not working (don’t know why) or i have some problem with my raspberry PI that i don’t know

Reddit - The heart of the internet

Also the configuration and the steps to configure in the right way (as said @mykepredko )

firmware/V3.0/Klipper/README.md

I also asked to ChatGPT how to change the documents /boot/config.txt and /boot/cmdline.txt

Here the steps to change it via SSH:

sudo nano /boot/firmware/cmdline.txt

sudo nano /boot/firmware/config.txt

Thank you very much to everyone, your contributions have been very helpful and I’m sure I wouldn’t have been able to do it without you, thanks again.

As a last question, do you know if it’s a very big downgrade to communicate between the raspberry PI and the SKR MINI through USART communication?

Thanks

[mykepredko]

@jordibc

Finally it’s working with USART comunication.

Congratulations, I’m happy that you have things working.

@jordibc

As a last question, do you know if it’s a very big downgrade to communicate between the raspberry PI and the SKR MINI through USART communication?

Looking at it from a practical operations perspective, you won’t see any difference.

The big advantage to USB over serial is that you should be able to buy a premade USB cable for a few bucks rather than wire your own serial connection.

Again, I’m glad you got things working.