TMC2660 - Random Off Time
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So I was reading through the TMC2660 datasheet, as you do, and noticed a section (9.2.1, page 36) about a "Random Off Time" which is meant to reduce the beat frequency that you get between the two unsynchronised current loops.
The datasheet isn't clear whether or not it can be used with the Spread Cycle mode than the Duet uses, but I was wondering if you guys had seen / tried this option with the aim of reducing noise ?
It looks like a constant is already defined for it in the firmware:
https://github.com/dc42/RepRapFirmware/blob/7df2717ebd680abf1b541dae800cfdc3b6298a02/src/DuetNG/TMC2660.cpp#L67 -
If you look at the source code carefully you will find there is an undocumented way of setting the TMC2660 chopper control register via GCode. Please use this carefully as it may be possible to damage the drivers by writing inappropriate values to that register.
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Ahh, that's a well hidden command.
I'll have a go at trying this option and will double check the settings in the datasheet before I do.
Have you tried these options or have you always just used the default Spread Cycle mode ?
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I have only used the default values.
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Fair enough, it sounds like a journey of discovery awaits me. I'll give it a try some time this week and report back.
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I've just tried all of the combinations of these settings:
Chopper mode = Spread cycle, Random TOFF time = Disabled (Default)
Chopper mode = Constant TOFF, Random TOFF time = Disabled
Chopper mode = Spread cycle, Random TOFF time = Enabled
Chopper mode = Constant TOFF, Random TOFF time = EnabledThe default is quietest, constant TOFF was slightly noisier and random TOFF was always noticeably noisier.
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Thanks for that report.
