In an attempt to resolve the issue in https://forum.duet3d.com/topic/35452/reading-general-purpose-inputs-in-duet-mini-5-returns-null, I upgraded the firmware on my new Duet Mini5+ from 3.0.something (not actually sure) to 3.4.6.
After a machine move, the steppers now make a loud continuous noise, but not continuous in the sense they're buzzing continuously, but the pitch and volume appears to randomly change.
I thought this must be because my configuration format was for an older firmware version, so I refreshed it using RRF config tool, but no change.
The axes still move and function correctly, but this is a significant difference in behaviour, so would really appreciate any input in getting to the bottom of it. Thanks!
EDIT - not sure how to post a response to my own question to show it as an answer... so just edited here instead. Issue resolved.
So, in config.g, in the M569 lines I've enabled stealthChop using the D3 flag, where previously the D3 flag was not provided. Presumably stealthChop was enabled by default in older firmware, and not in current firmware?
; Drives
M569 P0.0 D3 S1 ; physical drive 0.0 goes forwards