Motors "hissing" in idle after 3.4.0rc2

[thomas.weiss]

Hey,

we've been running a small CNC on firmware 3.3 for a couple of weeks without any major problems. Today I updated the Duet 3 mini 5+ to 3.4.0rc2.

From a functionality point of view, everything works fine, but while idle, the motors make an extremely loud "hissing" sound (a bit like "gas leaking"). This sound was also there while on 3.3, but it was barely noticeable even with an ear within a couple of centimeters from the motors. Now it's clearly audible all across the room.

The only thing I found in the changelogs that could be related to this is this entry:

[Duet 3 Mini] [Duet Maestro] The stepper drivers no longer default to stealthchop mode, because of the risk of excessive motor current if the correct tuning move is not executed

If this is causing the sounds, what would I need to change exactly to get back to the old behaviour? Add a 3 to each M569?

Here is our motor data:

Did anything change with 3.4 that could lead to this? We didn't do any changes to the config etc.

Still - here is our config:

; Configuration file for Duet 3 Mini 5+ (firmware version 3.3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.3.5 on Wed Nov 03 2021 10:22:11 GMT+0100 (Mitteleuropäische Normalzeit) 

; General preferences

M929 P"eventlog.txt" S1

G90                              ; send absolute coordinates...
M83                              ; ...but relative extruder moves
M550 P"CNC"                  ; set printer name

; Network
M552 P0.0.0.0 S1                 ; enable network and acquire dynamic address via DHCP
M586 P0 S1                       ; enable HTTP
M586 P1 S1                       ; enable FTP
M586 P2 S0                       ; disable Telnet

M575 P1 B57600 S0				 ; disable check-sums for UART communication

; Drives						 ; X:1 Y:2/3 Z:0
M569 P0.0 S1                     ; physical drive 0.0 goes forwards
M569 P0.1 S1                     ; physical drive 0.1 goes forwards
M569 P0.2 S0                     ; physical drive 0.2 goes backwards
M569 P0.3 S0                     ; physical drive 0.3 goes backwards

M584 X0.1 Y0.2:0.3 Z0.0              ; set drive mapping
M350 X16 Y16 Z16 I1              ; configure microstepping with interpolation

M92 X656.168 Y656.168 Z1007.874  ; set steps per mm
M566 X1000.00 Y1000.00 Z800.00   ; set maximum instantaneous speed changes (mm/min)
M203 X3000.00 Y3000.00 Z3000.00  ; set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z200.00     ; set accelerations (mm/s^2)
M906 X950 Y900 Z900              ; Lower motor currents

; Axis Limits
M208 X0 Y0 Z-55 S1                 ; set axis minima
M208 X150 Y130 Z20 S0            ; set axis maxima

; Endstops
M574 X2 P"!^io5.in" S1       ; configure switch-type (e.g. microswitch) endstop for low end on X via pin !^io0.in
M574 Y1 P"!^io2.in+!^io3.in" S1   ; configure switch-type (e.g. microswitch) endstop for low end on Y via pin !^io1.in
M574 Z2 P"!^io1.in" S1        ; configure switch-type (e.g. microswitch) endstop for low end on Z via pin !^io2.in

; Spindle
M950 R0 C"nil+io4.out" L20000
M563 P0 S"spindle" R0; define tool 0

; Laser
M950 P9 C"out6"
M42 P9 S0 ;Turn off laser

; Z-Probe
M558 P0 H5 F120 T6000            ; disable Z probe but set dive height, probe speed and travel speed
M557 X15:215 Y15:180 S20         ; define mesh grid

; Misc
M140 H-1                         ; disable heated bed (overrides default heater mapping) 
G10 X0 Y0 Z0 P0
M453 ; switch to cnc mode
T0                               ; select first tool

[thomas.weiss]

@thomas-weiss For anyone reading. Seems like the duet3 mini 5+ not defaulting to stealthchop anymore was the problem.

Adding a D3 to each M569 setting up the motors resolved the hissing sound.

If I missed anything that I should be doing, please let me know.

[dc42]

@thomas-weiss that's correct, the motors no longer default to stealthChop. The reason is that stealthChop doesn't work well unless you execute the proper tuning movement during homing.