# Cannot find MCU?
**URL:** https://klipper.discourse.group/t/cannot-find-mcu/20406
**Category:** General Discussion
**Created:** [December 2, 2024, 10:48pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406 "2024-12-02T22:48:16Z")
**Posts on this page:** 18
**Page:** 1
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 2, 2024, 10:48pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/1 "2024-12-02T22:48:16Z")
### Basic Information:
Printer Model: Ender 3
MCU / Printerboard: SKR3 V2 BTT
Host / SBC
klippy.log
[klippy (2).log](https://klipper.discourse.group/uploads/short-url/oCW8LDamahBsoNkdg3ghUSBLGki.log) (100.0 KB)
I already have a printer running klipper now excellently, so i wanted to upgrade my other printer to it as well.
I have a PI 4B flashed with mainsail and connected how ever the MCU to the board doesn’t work. I thought i fried the motherboard some how so i bought another one and its doing exactly the same.
I’ve got the same firmware i flashed my other printer with on a sd card inserted into the motherboard (both btt skr3 v2) so my logic is that if it worked on the other motherboard it should work on this?? its on the SD card as firmware.bin.
when I run ls /dev/serial/by-id/\* to get my MCU i get back /dev/serial/by-id/usb-LeafLabs\_Maple-if00 which i have in my printer.cfg.
I have no idea what else to do? any suggestions or help would be great!
Thank you
Klipper reports: ERROR
mcu ‘mcu’: Unable to connect
Once the underlying issue is corrected, use the
“FIRMWARE\_RESTART” command to reset the firmware, reload the
config, and restart the host software.
Error configuring printer
Also worth mentioning, the mother board isnt yet installed in the 3d printer, that and the Pi are sitting on my desk connect to each other, does that matter?
---
### Author:  [@EddyMI3D](https://klipper.discourse.group/u/EddyMI3D)
#### Post date: [December 3, 2024, 6:45am UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/2 "2024-12-03T06:45:00Z")
> [@3dprintnoob92](#):
>
> I’ve got the same firmware i flashed my other printer
Are those printers the same and do they have the same printer board?
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 7:26am UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/3 "2024-12-03T07:26:43Z")
Same printers, same boards.
---
### Author:  [@Sineos](https://klipper.discourse.group/u/Sineos)
#### Post date: [December 3, 2024, 9:55am UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/4 "2024-12-03T09:55:49Z")
> [@3dprintnoob92](#):
>
> when I run ls /dev/serial/by-id/\* to get my MCU i get back /dev/serial/by-id/usb-LeafLabs\_Maple-if00 which i have in my printer.cfg.
This indicates that Klipper is not correctly flashed on the board. See [Issues flashing the printer board](https://klipper.discourse.group/t/issues-flashing-the-printer-board/14015) and in particular make sure you configure for the MCU that is REALLY installed on your board.
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 2:11pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/5 "2024-12-03T14:11:03Z")
Please see images below. Thanks for your help, hope some of these give you a clue to what on earth i’ve gotta do resolve the issue.
Could it be a power supply issue as currently the Motherboard is only powdered by the Pi as i have not installed it in the printer?
---
### Author:  [@Sineos](https://klipper.discourse.group/u/Sineos)
#### Post date: [December 3, 2024, 2:28pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/6 "2024-12-03T14:28:31Z")
Unfortunately the screenshots are of no use and you cannot show the issue with screenshots.
Again: Your connection string `/dev/serial/by-id/usb-LeafLabs_Maple-if00` clearly indicates that the board is not flashed with Klipper.
Follow the instructions given in the link above and in particular verify that the MCU on your board is actually what you use for compiling the firmware.
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 2:49pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/7 "2024-12-03T14:49:19Z")
i was trying to show you that when i run the command to find my mcu out that it returns ‘/dev/serial/by-id/usb-LeafLabs\_Maple-if00’
you can also see that klipper is install on the pi and i have used winscp to extract the klipper.bin file install on the pi.
i have used 3 different sd cards all reformatted to fat32 along with 3 different cables, i have two of the same motherboards (btt skr e3 v2) both returning the same mcu ID.
i have double checed the chip is correct and the bootloader is also
---
### Author:  [@Sineos](https://klipper.discourse.group/u/Sineos)
#### Post date: [December 3, 2024, 2:51pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/8 "2024-12-03T14:51:23Z")
Show a screenshot of your `make menuconfig` settings and a screenshot of the printer board where the markings on the MCU can be read.
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 3:03pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/9 "2024-12-03T15:03:28Z")
this? and
?
thanks!
---
### Author:  [@Sineos](https://klipper.discourse.group/u/Sineos)
#### Post date: [December 3, 2024, 3:56pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/10 "2024-12-03T15:56:06Z")
How, when and where did you build the firmware for the board?
In doubt refer to [build-and-flash-the-firmware](https://klipper.discourse.group/t/installing-klipper-with-kiauh/10734#build-and-flash-the-firmware-12)
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 4:25pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/11 "2024-12-03T16:25:52Z")
I’ve just remade it and tried to flash it again and still getting the same.
---
### Author:  [@mykepredko](https://klipper.discourse.group/u/mykepredko)
#### Post date: [December 3, 2024, 4:48pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/12 "2024-12-03T16:48:52Z")
Sorry for interjecting here but the size of `klipper.bin` doesn’t look right.
I just built my own version of the firmware using the instructions here:
>
and selecting the 'F429:
and then when I look in the `~/klipper/out` directory:
```auto
Version: v0.12.0-379-gf2e69a370
Preprocessing out/src/generic/armcm_link.ld
Linking out/klipper.elf
Creating hex file out/klipper.bin
orangepi@orangepicm4:~/klipper$ ls out -l
total 1708
-rw-r--r-- 1 orangepi orangepi 11488 Dec 3 16:41 autoconf.h
lrwxrwxrwx 1 orangepi orangepi 32 Dec 3 16:41 board -> /home/orangepi/klipper/src/stm32
drwxr-xr-x 2 orangepi orangepi 4096 Dec 3 16:41 board-generic
-rw-r--r-- 1 orangepi orangepi 27 Dec 3 16:41 board-link
-rw-r--r-- 1 orangepi orangepi 72794 Dec 3 16:42 compile_time_request.c
-rw-r--r-- 1 orangepi orangepi 353 Dec 3 16:42 compile_time_request.d
-rw-r--r-- 1 orangepi orangepi 227784 Dec 3 16:42 compile_time_request.o
-rw-r--r-- 1 orangepi orangepi 17771 Dec 3 16:42 compile_time_request.txt
-rwxr-xr-x 1 orangepi orangepi 31872 Dec 3 16:42 klipper.bin
-rw-r--r-- 1 orangepi orangepi 9382 Dec 3 16:42 klipper.dict
-rwxr-xr-x 1 orangepi orangepi 1373188 Dec 3 16:42 klipper.elf
drwxr-xr-x 4 orangepi orangepi 4096 Dec 3 16:41 lib
drwxr-xr-x 4 orangepi orangepi 4096 Dec 3 16:42 src
```
As I understand it, Klipper firmware for basically any MCU should not be less than 30k.
What is the process (and parameters) that you used for building your version of Klipper?
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 4:58pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/13 "2024-12-03T16:58:46Z")
hello, thanks for your help!
i used make config in the klipper directory
>
I have the skr mini e3 v2 motherboard.
---
### Author:  [@mykepredko](https://klipper.discourse.group/u/mykepredko)
#### Post date: [December 3, 2024, 5:35pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/14 "2024-12-03T17:35:25Z")
> [@3dprintnoob92](#):
>
> I have the skr mini e3 v2 motherboard.
This is why we ask people to be precise with the information that they provide - You did not specify “SKR Mini E3 V2” in the original post. Grumble.
Regardless, two comments:
1. Could you do a `ls ~/klipper/out -l` and see if it matches:
```auto
orangepi@orangepicm4:~/klipper$ ls out -l
total 1420
-rw-r--r-- 1 orangepi orangepi 11484 Dec 3 17:15 autoconf.h
lrwxrwxrwx 1 orangepi orangepi 32 Dec 3 17:15 board -> /home/orangepi/klipper/src/stm32
drwxr-xr-x 2 orangepi orangepi 4096 Dec 3 17:15 board-generic
-rw-r--r-- 1 orangepi orangepi 27 Dec 3 17:15 board-link
-rw-r--r-- 1 orangepi orangepi 66579 Dec 3 17:16 compile_time_request.c
-rw-r--r-- 1 orangepi orangepi 353 Dec 3 17:16 compile_time_request.d
-rw-r--r-- 1 orangepi orangepi 217612 Dec 3 17:16 compile_time_request.o
-rw-r--r-- 1 orangepi orangepi 16013 Dec 3 17:16 compile_time_request.txt
-rwxr-xr-x 1 orangepi orangepi 29644 Dec 3 17:16 klipper.bin
-rw-r--r-- 1 orangepi orangepi 8426 Dec 3 17:16 klipper.dict
-rwxr-xr-x 1 orangepi orangepi 1096416 Dec 3 17:16 klipper.elf
drwxr-xr-x 4 orangepi orangepi 4096 Dec 3 17:15 lib
drwxr-xr-x 4 orangepi orangepi 4096 Dec 3 17:16 src
```
This is what I got when I built with your parameters and maybe the Folder view that you are using is rounding the size but even with that there seems to be a discrepancy there.
1. If you’re comfortable that the build is correct, could you try building with pin PA13 (SWDIO) set? This will turn on the STATUS LED on the board:
If you turn on/off the STATUS LED in your firmware, you will get a positive indication that you are changing the firmware.
Normally when the board turns on, you will get one LED lit on the left side of the LED that I’ve marked here:
If PA13 is set and the BTT SKR Mini E3 V2 is programmed correctly, then you’ll have both LEDs lit.
If they’re both set then you can follow the instructions @Sineos and @EddyMI3D are giving you, knowing that you are updating the firmware on your main controller board.
---
### Author:  [@Sineos](https://klipper.discourse.group/u/Sineos)
#### Post date: [December 3, 2024, 5:51pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/15 "2024-12-03T17:51:48Z")
Make sure to:
- rename to `firmware.bin`
- the SD card is formatted as FAT32. In doubt use [SD Memory Card Formatter for Windows/Mac | SD Association](https://www.sdcard.org/downloads/formatter/)
- the SD card is 8GB or less
- Not fully sure here, but typically the BTT boards rename the `firmware.bin` file to `firmware.cur` on a successful flash
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 8:58pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/16 "2024-12-03T20:58:55Z")
Hello, Sorry for the slow reply
Here is what i got below.
i will have a go at the PA13 now.
Sorry for not being more specific on my board!
---
### Author:  [@3dprintnoob92](https://klipper.discourse.group/u/3dprintnoob92)
#### Post date: [December 3, 2024, 9:13pm UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/17 "2024-12-03T21:13:29Z")
both lights are on now
and…
Success!
Thank you mykepredko, Sineos & EddyMI3D! I was truly out of my depth
---
### Author:  [@system](https://klipper.discourse.group/u/system)
#### Post date: [January 3, 2025, 7:13am UTC](https://klipper.discourse.group/t/cannot-find-mcu/20406/18 "2025-01-03T07:13:47Z")
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