Interpolation possible not working on DUET boards?

Vlad · 20 Aug 2019, 09:32

Ok, here is another problem I discovered on this boards. 256 microsteping sounds completely different from x64 for example. When I tested interpolation, I tested different settings. Such as

128 I0 vs 128 I1
64 I0 vs 64 I1
Actually I tried all the way down to 4X microstepping which is super noisy, and turning on interpolation does absolutely nothing to the way stepper moves and to the sound and noise it produces.

Please tell me if I am wrong and this is how Interpolation is supposed to function. I did try this same function on smoothieboard last year, and I remember clearly how turning on interpolation immediately reduced noise even at relatively low microstepping.

Has anyone tested this at all? It totally feels like it is simply not functioning properly.

nhof · 20 Aug 2019, 09:43

My understanding is that the interpolation only works with steps set to 16x, which will then be interpolated on the hardware to 256x

So 16 I1 should be the only command to actually use the interpolation.

Note that this is a hardware limitation of the TMC driver and not a firmware limitation.

deckingman · 20 Aug 2019, 10:26

@vlad From the Duet Wiki here https://duet3d.dozuki.com/Wiki/Gcode#Section_M350_Set_microstepping_mode

Quote

"Inn Enable (nn=1) or disable (nn=0) microstep interpolation mode for the specified drivers, if they support it. The Duet 2 WiFi/Ethernet support interpolation (to x256 microstepping) only when configured for x16 microstepping. The Duet 2 Maestro supports interpolation at all microstep settings."

droftarts · 20 Aug 2019, 10:29

For the Duet Wifi/Ethernet, it's a limitation of the stepper driver, only 16x microstepping can have interpolation. :
"Super quiet TMC2660 stepper drivers: SPI controlled and capable of up to 256 microstepping with optional 16x interpolation when using 16x microstepping. Hardware support for variable microstepping and variable stepper current for optimum speed and power efficiency."
https://duet3d.dozuki.com/Wiki/Hardware_Overview#Section_Duet_2_Wifi

It's the Duet Maestro that can have interpolation on any microstepping:
"Super quiet TMC2224 stepper drivers: SPI controlled and capable of up to 256 microstepping with optional interpolation from any lower microstepping setting to x256."
https://duet3d.dozuki.com/Wiki/Duet_2_Maestro_Hardware_Overview#Section_Features

Ian

Vlad · 20 Aug 2019, 11:21

@droftarts wow, lots of useful info, thank you guys a lot! I guess I am gonna try X16 again then and see if it helps. I print at 200mm/s usually and with aggressive accelerations etc, so what is not noisy at 80mm/s becomes 4x noisier at 200 and at 400 travel speed So, I am trying to further optimize the printer.

mrehorstdmd · 20 Aug 2019, 11:40

@vlad I have recently done some testing on speed and high microstepping ratios in my corexy sand table mechanism. I found that at motor speeds under 1.5 revs/sec, high microstepping ratios quiet down the motors, but if you get above that, it doesn't help much, if at all.

The interpolation is iffy during acceleration and deceleration, but you can operate at higher microstepping ratios without interpolation. Doing so will bump into the maximum pulse rate of 120 kHz at lower speeds than using interpolation.

I'm redesigning the drive mechanism to step up the motor revs by 5x so that I can use 256:1 ustepping and still get 500 mm/sec from the table and have it run quietly. I don't think that would be practical in a 3D printer, but in a low drag, low precision mechanism like a sand table it should work fine.

Vlad · 20 Aug 2019, 11:48

@mrehorstdmd yep, not gonna be practical in 3D printer, but still a good info! Thanks for sharing! At my speeds it's pretty noisy regardless, that is true

mrehorstdmd · 20 Aug 2019, 19:57

@vlad You can always get 3 or 5 phase steppers and drivers. They tend to get pricey, but they're out there and if you look enough you might be able to find some surplus parts for reasonable $.

Vlad · 21 Aug 2019, 02:30

@mrehorstdmd good idea actually, I will have a look at those. I can get them directly from MOONS' for reasonable price usually, ship to my office in China and then get them to me here in California pretty quick.

Vlad · 21 Aug 2019, 07:31

@droftarts just tested with X16 Io and X16 I1. No, interpolation is officially not working on these boards at any setting. @dc42 have you guys tested that?

dc42 · 21 Aug 2019, 07:34

@vlad said in Interpolation possible not working on DUET boards?:

@droftarts just tested with X16 Io and X16 I1. No, interpolation is officially not working on these boards at any setting. @dc42 have you guys tested that?

Interpolation definitely works, my delta is much louder without it. Make sure that you are using the right parameter before the digit-1, i1 or I1 (letter-i), not l1 (letter-L) or |1 (vertical bar).

deckingman · 21 Aug 2019, 09:29

To add to what @dc42 has said, interpolation definitely does work for hundreds if not thousand of us other users. You wrote this (quote) ..........

"just tested with X16 Io and X16 I1. No, interpolation is officially not working on these boards at any setting. @dc42 have you guys tested that?"

...........which shows that you used a lower case "o" rather than a zero. Perhaps you should spend a bit more time reading the documentaion and checking your own typing, and a bit less time trying to blame the firmware or hardware for the mistakes that you keep making.

Vlad · 21 Aug 2019, 09:38

@deckingman omg don't be a dummy please, you really think I don't know the difference. I type fast here, and it's a simple typo. How stupid you think people here are that I would run into "o" problem. Gosh...

If I ever need to hear some top stupid advice, i now know who to ask. Thanks! (but facepalm).

P.S: when you are at level of thinking people confuse O with 0, then probably you can not possibly notice that Interpolation simply is not active regardless of firmware command. So is it possible that your interpolation "works" because you have no idea how to test that? And now you speak for "thousands" of others apparently.

droftarts · 21 Aug 2019, 10:13

@Vlad Just out of curiosity, but how are you testing the interpolation is (or isn't) working? Doing a really slow move and listening for the steps? Going really fast and listening for a difference in noise? Oscilloscope? Would be good to know how to test this.

Also, what firmware are you on? And if you have a interpolation test gcode, please share.

Ian

deckingman · 21 Aug 2019, 10:14

@vlad said in Interpolation possible not working on DUET boards?:

@deckingman omg don't be a dummy please, you really think I don't know the difference. I type fast here, and it's a simple typo. How stupid you think people here are that I would run into "o" problem. Gosh...

If I ever need to hear some top stupid advice, i now know who to ask. Thanks! (but facepalm).

P.S: when you are at level of thinking people confuse O with 0, then probably you can not possibly notice that Interpolation simply is not active regardless of firmware command. So is it possible that your interpolation "works" because you have no idea how to test that? And now you speak for "thousands" of others apparently.

Experience has taught me that when people resort to throwing insults, it's generally a good indication that they have lost an argument and don't have the courage to admit that they were wrong. Either that or they simply lack the intelligence to formulate a sensible reply.

Fact1 - You tried to use interpolation at micro-stepping settings that do not support it. Had you bothered top read the documentation, this would have been clear to you but instead, you blame the firmware.
Fact 2. You used a lower case "o" in your post instead of a zero. Again, that is another irrefutable mistake on your part.

You can throw as many insults as you like, but for me the facts speak for themselves.

Vlad · 22 Aug 2019, 00:58

@deckingman assuming that someone is dumb to a level of using a letter instead of number is disrespectful and an insult. It is probably your reality of life to make such idiotic mistakes, and you totally consider that possible with other people, for me your assumption was quite autistic. So you got what you totally deserved. Blame yourself. Look at the keyboard where o and 0 is located. I am not programming a firmware on this forum, I am messaging, don't act like a complete idiot, for god's sake. I hate such "men". Really like a little spoiled girl, what a shame. It's super idiotic to even assume that I could use "o". Period. But what could I expect from a guy who had time to have 4300 posts anyways lol.

A Former User · 22 Aug 2019, 03:20

I would think as a guy who sells cloned boards pointing to www.duet3d.com you would appreciate deckingmans efforts to help random strangers on this forum, and maybe you should spend your time looking into if the silkscreening on your cloned boards is really in accordance with the OSH license as you claim instead of throwing insults at the guy who bothered to read the documentation for you?

Just a suggestion before this thead gets closed down..

Veti · 22 Aug 2019, 05:37

@vlad said in Interpolation possible not working on DUET boards?:

assuming that someone is dumb to a level of using a letter instead of number is disrespectful and an insult.

but you did do that just a few post above, so he did not make any assumption there.

droftarts · 22 Aug 2019, 08:50

@Vlad is it one of your boards that you're having this problem with, or a genuine board? Again, please post your testing method and gcode so we can test what you're seeing.

Ian