# Error mcu buffer\_mcu: Unable to connect
**URL:** https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497
**Category:** Sovol SV08 MAX
**Tags:** firmware, advice
**Created:** [August 10, 2025, 1:58pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497 "2025-08-10T13:58:47Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 10, 2025, 1:58pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/1 "2025-08-10T13:58:47Z")
hello everybody đ
i received and assembled my sv 08 max a few days ago, but the only thing i get after startup is a message ââmcu buffer\_mcu : Unable to connectââ and i am at a loss. i checked all the reachable connectors, unplugged and replugged them, and looked for an input voltage switch (i could not find one, here in germany it would have to be set to 230 v). can anyone pls. get me into the right direction or help me fix this ? thank you all very much in advance
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 10, 2025, 7:13pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/2 "2025-08-10T19:13:37Z")
> [@AlwinA](#):
>
> input voltage switch (i could not find one
It appears the power supply is âself switchingâ.
Do you have network connection (wired or wifi) to the printer?
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 10, 2025, 10:12pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/3 "2025-08-10T22:12:02Z")
hello, thanks for your reply. ok, the input voltage isnât causing the problem, then.
yes, the printer is connected to ethernet/lan (and i checked the connection with a notebook, dhcp works, internet is available)
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 10, 2025, 11:08pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/4 "2025-08-10T23:08:47Z")
You shoud open a support ticket. Email [info@sovol3d.com](mailto:info@sovol3d.com). Include your order number.
While you are waiting for a reply you can try the following:
Put the printer IP in your browser. Does Mainsail show up?
Find your MCU
[Query devices | Mainsail](https://docs.mainsail.xyz/overview/features/query-devices).
Then go to the [Machine] tab and click on printer.cfg to open it in Mainsailâs built in editor. Edit printer.cfg with the correct address, save and restart.
OR connect with Putty (or ssh ap of your choice)
User sovol
Password sovol
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 1:54am UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/5 "2025-08-11T01:54:47Z")
thank you very much again, for your help đ
i emailed the support, and via their fb-messenger. i have no order no. - i bought the printer on the sovol kickstarter campaign as early bird offer. i have a few emails from kickstarter/pledgebox, and of course the visa invoice with the purchase (kickstarter com chung hk 915.46 eur) but nowhere there is a order no. to be found. my backer no. is 455 âš
yep, mainsail is coming up - and now i have to make a confession. i come from a anet a8, e10, anycubic i3 mega, a prusa mk3s now 3.9, a bambulab x1c and prusa xl 2t. i finished building a fystec voron 2.4 kit in november, but i am too dumb to get the software running, so i am a complete newbie regarding klipper âš
following the printer.cfg of the sv 08 max - but i have no idea what adress i have to change ???
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 1:55am UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/6 "2025-08-11T01:55:34Z")
[include mainsail.cfg]
#[include chamber\_hot.cfg]
[include buffer\_stepper.cfg]
[include timelapse.cfg]
[include plr.cfg]
[include Macro.cfg]
[include moonraker\_obico\_macros.cfg]
[mcu]
canbus\_uuid: 0d1445047cdd
[mcu extra\_mcu]
canbus\_uuid: 61755fe321ac
[temperature\_sensor mcu\_temp]
sensor\_type: temperature\_mcu
min\_temp:0
max\_temp:110
[temperature\_sensor Host\_temp]
sensor\_type: temperature\_host
min\_temp: 0
max\_temp: 110
[temperature\_sensor Toolhead\_Temp]
sensor\_type: temperature\_mcu
sensor\_mcu: extra\_mcu
[virtual\_sdcard]
path:/home/sovol/printer\_data/gcodes/
[exclude\_object]
[printer]
kinematics: corexy
max\_velocity: 700
max\_accel: 40000
max\_accel\_to\_decel: 10000
max\_z\_velocity: 10
max\_z\_accel: 500
square\_corner\_velocity: 5.0
[lis2dw]
cs\_pin: extra\_mcu:PB12
spi\_software\_sclk\_pin: extra\_mcu:PB13
spi\_software\_mosi\_pin: extra\_mcu:PB15
spi\_software\_miso\_pin: extra\_mcu:PB14
axes\_map: x,z,y
[resonance\_tester]
accel\_chip: lis2dw
probe\_points:
250, 250, 30
accel\_per\_hz:100
min\_freq: 35
max\_freq: 45
max\_smoothing: 0.25
hz\_per\_sec: 1.0
[input\_shaper]
damping\_ratio\_x: 0.001
damping\_ratio\_y: 0.001
[probe\_eddy\_current eddy]
sensor\_type: ldc1612
z\_offset: 3.50
i2c\_mcu: extra\_mcu
i2c\_bus: i2c2
x\_offset: -19.8
y\_offset: -0.75
vir\_contact\_speed: 3.0
[bed\_mesh]
speed: 400
horizontal\_move\_z: 1.5
algorithm: bicubic
mesh\_min: 13,15
mesh\_max: 476,490
probe\_count: 60,60
fade\_start: 0
fade\_end: 10
scan\_overshoot: 4
[z\_offset\_calibration]
non\_contact\_probe:probe\_eddy\_current eddy
contact\_probe:probe\_eddy\_current eddy
endstop\_xy\_position: 250,251
z\_hop: 5
z\_hop\_speed: 10
internal\_endstop\_offset: -0.25
[quad\_gantry\_level]
gantry\_corners:
-70,-40
550,600
points:
50, 30
50, 470
490, 470
490, 30
speed: 400
horizontal\_move\_z: 10
retry\_tolerance: 0.1
retries: 15
max\_adjust: 20
[safe\_z\_home]
home\_xy\_position: 277,251
speed: 150.0
z\_hop: 10
z\_hop\_speed: 10.0
[stepper\_x]
step\_pin: PE1
dir\_pin: PD7
enable\_pin: !PD5
rotation\_distance: 40
microsteps: 16
full\_steps\_per\_rotation: 200
endstop\_pin: ^extra\_mcu:PA10
position\_min: -11
position\_endstop: -11
position\_max: 502
homing\_speed: 120
homing\_retract\_dist: 3
homing\_retract\_speed: 15.0
[tmc5160 stepper\_x]
cs\_pin: PE0
spi\_software\_mosi\_pin: PB6
spi\_software\_miso\_pin: PB5
spi\_software\_sclk\_pin: PB4
interpolate: false
run\_current: 3.0
sense\_resistor: 0.05
stealthchop\_threshold: 0
[stepper\_y]
step\_pin: PD3
dir\_pin: PD2
enable\_pin: !PD0
rotation\_distance: 40
microsteps: 16
full\_steps\_per\_rotation: 200
endstop\_pin: ^PD1
position\_min: -1
position\_endstop: 505
position\_max: 505
homing\_speed: 120
homing\_retract\_dist: 3
homing\_retract\_speed: 15.0
[tmc5160 stepper\_y]
cs\_pin: PD4
spi\_software\_mosi\_pin: PB6
spi\_software\_miso\_pin: PB5
spi\_software\_sclk\_pin: PB4
interpolate: false
run\_current: 3.0
sense\_resistor: 0.05
stealthchop\_threshold: 0
[stepper\_z] #z1
step\_pin: PA8
dir\_pin: PC9
enable\_pin: !PA10
rotation\_distance: 40
gear\_ratio: 80:12
microsteps: 16
endstop\_pin: probe: z\_virtual\_endstop
position\_max: 505
position\_min: -10
homing\_speed: 10.0
homing\_retract\_dist: 5.0
homing\_retract\_speed: 10.0
second\_homing\_speed: 5.0
[tmc2209 stepper\_z]
uart\_pin: PA9
interpolate: true
run\_current: 1.2
sense\_resistor: 0.150
uart\_address:3
stealthchop\_threshold: 999999
[stepper\_z1] #z2
step\_pin: PC6
dir\_pin: !PD15
enable\_pin: !PC8
rotation\_distance: 40
gear\_ratio: 80:12
microsteps: 16
[tmc2209 stepper\_z1]
uart\_pin: PC7
interpolate: true
run\_current: 1.2
sense\_resistor: 0.150
uart\_address:3
stealthchop\_threshold: 999999
[stepper\_z2] #z3
step\_pin: PA5
dir\_pin: PA4
enable\_pin: !PA7
rotation\_distance: 40
gear\_ratio: 80:12
microsteps: 16
[tmc2209 stepper\_z2]
uart\_pin: PA6
interpolate: true
run\_current: 1.2
sense\_resistor: 0.150
uart\_address:3
stealthchop\_threshold: 999999
[stepper\_z3] #z4
step\_pin: PB13
dir\_pin: !PB12
enable\_pin: !PB15
rotation\_distance: 40
gear\_ratio: 80:12
microsteps: 16
[tmc2209 stepper\_z3]
uart\_pin: PB14
interpolate: true
run\_current: 1.2
sense\_resistor: 0.150
uart\_address:3
stealthchop\_threshold: 999999
[adc\_temperature extruder\_thermistor]
temperature1:25
resistance1:1268.60
temperature2:180
resistance2:1920.98
temperature3:300
resistance3:2398.52
[extruder]
step\_pin: extra\_mcu:PA8
dir\_pin: extra\_mcu:PA9
enable\_pin:!extra\_mcu:PA11
rotation\_distance: 6.5
microsteps: 16
full\_steps\_per\_rotation: 200
nozzle\_diameter: 0.400
filament\_diameter: 1.75
max\_extrude\_only\_distance: 150
max\_extrude\_cross\_section: 60
heater\_pin:extra\_mcu:PB7
sensor\_type:extruder\_thermistor
pullup\_resistor: 11500
sensor\_pin: extra\_mcu:PA5
min\_temp: -0
max\_temp: 310
max\_power: 1.0
min\_extrude\_temp: 150
control : pid
pid\_kp : 34.838
pid\_ki : 4.976
pid\_kd : 62.823
pressure\_advance: 0.025
pressure\_advance\_smooth\_time: 0.035
[tmc2209 extruder]
uart\_pin: extra\_mcu:PA12
interpolate: True
run\_current: 0.8
uart\_address:3
sense\_resistor: 0.150
[verify\_heater extruder]
max\_error: 120
check\_gain\_time:30
hysteresis: 10
heating\_gain: 2
[thermistor bed\_thermistor]
temperature1: 25
resistance1: 100000
temperature2: 50
resistance2: 18085.4
temperature3: 100
resistance3: 5362.6
[heater\_bed]
heater\_pin: PD12
sensor\_type: bed\_thermistor
sensor\_pin: PC5
max\_power: 1.0
min\_temp: -0
max\_temp: 110
control : pid
pid\_kp : 73.571
pid\_ki : 1.820
pid\_kd : 783.849
[verify\_heater heater\_bed]
max\_error: 120
check\_gain\_time: 90
hysteresis: 10
heating\_gain: 1
[fan\_generic fan0] # front model cool fan
pin: extra\_mcu: PB0
max\_power: 1.0
[fan\_generic fan1] # back model cool fan
pin: extra\_mcu: PA7
max\_power: 1.0
[fan\_generic fan2] # auxiliary fan
pin: PB0
max\_power: 1.0
[fan\_generic fan3] # exhaust fan
pin: PE11
max\_power: 1.0
[output\_pin main\_led]
pin: PD13
value: 1.0
[heater\_fan hotend\_fan]
pin: extra\_mcu: PA6
max\_power: 1.0
kick\_start\_time: 0.5
heater: extruder
heater\_temp: 45
tachometer\_pin:extra\_mcu: PA1
tachometer\_ppr: 1
tachometer\_poll\_interval: 0.0013
[heater\_fan bed\_fan]
pin: PE14
max\_power: 1.0
kick\_start\_time: 0.5
heater: heater\_bed
heater\_temp: 35
tachometer\_pin: PB10
tachometer\_ppr: 2
tachometer\_poll\_interval: 0.001375
[gcode\_arcs]
resolution: 1.0
[idle\_timeout]
gcode: \_IDLE\_TIMEOUT
timeout: 1800
[save\_variables]
filename =/home/sovol/printer\_data/config/saved\_variables.cfg
#_# \<---------------------- SAVE\_CONFIG ----------------------\>
#_# DO NOT EDIT THIS BLOCK OR BELOW. The contents are auto-generated.
#_#
#_# [input\_shaper]
#_# shaper\_type\_x = mzv
#_# shaper\_freq\_x = 44.8
#_# shaper\_type\_y = mzv
#_# shaper\_freq\_y = 39.4
#\*#
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 2:27am UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/7 "2025-08-11T02:27:28Z")
Follow the instructions at the Mainsail link above
Your printer has 3 different MCUs. Each will have an address similar to
```auto
canbus_uuid: 0d1445047cdd
```
The mainboard MCU is referred to as mcu
The toolhead MCU extra\_mcu
And the buffer (filament pusher) buffer\_mcu
Note: the CAN address for the buffer\_mcu is in the buffer\_stepper.cfg file but still has to be correct.
The error you posted seems to be associated with the mainboard.
It is more likely that the MCU is not connected at all but it is still a good idea to try and find it with the Mainsail routine.
Does Mainsail find any can devices?
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 12:39pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/8 "2025-08-11T12:39:31Z")
hello,
devices lists the following:
CAN0 KLIPPER 61755fe321ac
USB KLIPPER stm32h750xx CAN Adapter 1d50:606f
USB 2.0 Camera 32e6:9221
VIDEO V4L2 USB 2.0 Camera /dev/video0
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 12:42pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/9 "2025-08-11T12:42:44Z")
as i understand this, only unassigned devices are shown, right ? so the ââmcu extra\_mcuââ can not connect ? meaning wiring between toolhead board and mainboard has a problem ?
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 3:43pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/10 "2025-08-11T15:43:10Z")
I think you are right.
In printer.cfg Iâd comment out
```auto
[mcu extra_mcu]
canbus_uuid: 61755fe321ac
```
By putting a # in front of them. Save and restart.
The error message should to âmissing pinâ or some such.
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 3:48pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/11 "2025-08-11T15:48:13Z")
WHOOPS
I just reread your original post
BUFFER is referring to the filament pusher NOT an internal software registerâŚ
Your issue is with the pusher not the toolhead
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 7:44pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/12 "2025-08-11T19:44:09Z")
hello cardoc, the sovol support did reply to my error message, and they confirm that the auxiliary buffer is at fault, either the device or its connection to the mainboard are not working properly. they had me check all connections again, but that fixed nothing.
i googled some more and out-commented the line
[include buffer\_stepper.cfg]
with a # in the printer.cfg, and now the machine ist starting. i have no idea if it will print or throw an error missing the axiliary buffer, but i will check. for now a managed a complete calibration, so things are lighten up đ
thank you so much for your kind help đ
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 9:11pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/13 "2025-08-11T21:11:35Z")
Glad to have helped.
Just wish Iâd have picked up âbufferâ was a device name not a generic software reference. Could have saved 2 days.
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 9:32pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/14 "2025-08-11T21:32:31Z")
Donât worry about that - i am so raw and new with Klipper that any help is greatly appreciated đ and i am in no hurry, my X1C and XL are working perfectly.
if i may, and not seem to be too intrusive, would you consider helping me getting my voron 2.4 (build is complete but for the software) to start printing ? if so, i happily offer a donation via paypal if that can be successfully completed đ and also no hurry in any way, the machine lies on its back behind me on a bench for 8 months now, i would have to dive in again before we can even start đ
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 9:34pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/15 "2025-08-11T21:34:23Z")
Getting a Max to run with the buffer\_mcu missing wonât be easy. The main printer.cfg is clean but MANY macros have calls to functions in buffer\_stepper.cfg
M400, M600, PAUSE, LOAD\_FILAMENT, UNLOAD\_FILAMENT are all going to error.
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 9:35pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/16 "2025-08-11T21:35:59Z")
oh, that is sad to hear - i will have to wait for sovol to send me a buffer unit or the buffer\_mcu then âš
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 9:43pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/17 "2025-08-11T21:43:38Z")
> [@AlwinA](#):
>
> would you consider helping me getting my voron 2.4 (build is complete but for the software) to start printing
Sure but for that find me (and several MUCH more knowledgeable folks) on [General Discussion - Klipper](https://klipper.discourse.group/c/general-discussion/6)
NOTE to others. The folks at link that have a hard and fast rule about âdirtyâ forks of Klipper. Only post there if you are on âmainlineâ.
No charge, Iâll rely on karma to balance any debts.
---
### Author:  [@cardoc](https://forum.sovol3d.com/u/cardoc)
#### Post date: [August 11, 2025, 9:48pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/18 "2025-08-11T21:48:21Z")
> [@AlwinA](#):
>
> that is sad to hear - i will have to wait for sovol to send me a buffer unit or the buffer\_mcu then âš
Go in and rename macros.cfg to max\_macros.cfg then upload the attached file from a âregularâ SV08.
Donât know if itâll work but there is only one way to know.
[Macro.cfg](https://forum.sovol3d.com/uploads/short-url/txm3Hradn0LhMeyiEQ4rFLMPcUA.cfg) (19.6 KB)
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 10:06pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/19 "2025-08-11T22:06:20Z")
i will, thank you - and wish you the best Karma đ
---
### Author:  [@AlwinA](https://forum.sovol3d.com/u/AlwinA)
#### Post date: [August 11, 2025, 10:07pm UTC](https://forum.sovol3d.com/t/error-mcu-buffer-mcu-unable-to-connect/8497/20 "2025-08-11T22:07:13Z")
thats a great idea - i will try that tomorrow, tks.
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