external driver "iHSS60" connection-question

A Former User

@dc42
Thanks so much!
First I tried with this setting but nothing then the "Alarm"-Led was on... then slightly increased the time-amounts to:
M569 P5 S1 R1 T2.51:2.51:6.01:0
M569 P6 S1 R1 T2.51:2.51:6.01:0

NOW IT WORKS! Yuhuu!

BUT...
sadly somehow the step-amount does not correspond to the moved amount in mm...? I double and triple checked all calculations with several approaches for checking in microsteps etc. but always get 83mm instead of 100mm, at least the error is consistent on both axis (x & y both have the external motor) and is also consistend independent of micro-steps-numbers, e.g. same error if set to 1/16 oe 1/256...

(So question:
Since my setup has a weired number of microsteps (34 tooth pulley but motor with 1:2 gearing before equals to 34/2="17"tooth pulley on a 2mm-pitch beltdrive with the 200stps-motor set to 256 internal microstepping (51200 m-stps) =ca. 1505,88235294118000000000 mircosteps per millimeter) I assume the error could be a rounding error (?) can the number of (micro-)steps per millimeter given finer then with two digits after the decimal point to avoid those rounding errors on the 700mm long axis...?)EDIT: NO, calculated the total error introduced by rounding to two decimals after point (leaving out 0,00235294118 each mm) is less than 2 microsteps on the 700mm; with 1505,88 microsteps in total per millimeter this is not measurable...

What else is my error? Has it to do with the timing to the external motor?

Best, Lucas

dc42

It's most unlikely that you will be able to use x256 microstepping using external drivers because of the extended pulse timing needed, unless you accept very slow maximum speeds. I suggest you reduce the microstepping in your external drivers to get a steps/mm of 300 or less.

Any microstepping you select with M350 is ignored for axes using external drivers.

M569 T parameters are rounded up to the next available multiple of 1.067 microseconds. So I don't know why those small changes you made had any effect.

I am surprised you needed to use the R1 option, because the expansion breakout board inverts the enable signal already.

A Former User

@dc42
Thanks for getting back so fast and all your support.
Got that already a few posts earlier from you, so M350 since a few days does not define anything here anymore for the external drive - since then when writing in the context of micro-stepping for the external dirves, I mean the micro-steps adjusted via dip-switches on the external-drives, e.g. setting the external motor for 1/256 (51200) microstepping via dip-switches and sending then in config.g "M92 X1505.88 Y1505.88" or putting the dip-switches to 1/16 (3200) and sending "M92 X94,12 Y94,12"

BUT on both settings, same error: ca. 83mm instead of 100, & also when using a micrometer I get 0,83mm instead of 1,00mm, so I have a repeatable error independent of microstepping (1/16 or 1/256...) and independent of micro-steps or big steps (0,1mm or 100mm)... but when I use https://www.prusaprinters.org/calculator/ this is what I had to put into it... will try with 0,01 more in the timing and report back

dc42

Are you certain that the belt is 2mm pitch, that the pulleys have 34 teeth, and the motor gearing is exactly 2:1? It's unusual to have gears in exact ratios like that. Usually the numbers of pulley teeth the gears are two relatively prime numbers.

A Former User

@dc42

That is the same that I thought... scratching my head and checking my e-mails if I ordered something else then what I thought I did...

Belt
gates-gt3-powergrip-2mgt (beware this is the gates 3rd gen(?) powergrip belt with 2m pitch meaning 2mm! They are available as 2mgt, 3mgt, 5mgt and 8mgt standing for the pitch in metric (mm) with GT-profile. Do not confuse with other naming conventions as gt3 belts with 3mm)
Measured the belt with caliper: 5 pitches are exactly 10mm... (5 pitches with 3mm would have been 15mm - I would have spotted that... )

Pulleys
GPK68MR2090-A-P8-KC90 (68tooth on a 8mm axis)
GPK34MR2090-B-P8-KC90 (34tooth on a 8mm axis)
(praised by misumi as pulleys for "gates gt3 powergrip 2mgt" belts...)
68/34 is 2/1...

I am using the same belt and pulleys on the z-axis to sync 2 pieces of tr2-spindles and there all calculation works out perfect... measured the z-axis with a borrowed micrometer: Only when changing directions the error is 0,03mm (slack in the 1830mm long belt), when moving in the same direction the error is less than 0,01mm (can not measure any... ) even after 100mm movements

Just tried to give all timings +0.01, did not change anything...
What exactly does hold? And could it be the communication-frequency? Datasheet says "pulse frequency max 200K" and "communication rate 57.6Kbps" (but I guess that is for the 232 Serial Communication Interface?)

Could that be something?

The drive-config in the config.g:

; Drives config
; seems to be: 0=X, 1=Y, 2=Z, 3=e0, 4=e1, 5=e2(exp-pcb:Drv5), 6=e3(exp-pcb:Drv6), ... see https://duet3d.dozuki.com/Wiki/Using_external_stepper_motor_drivers
M569 P2 S0 ; Drive 2=Z; S1 = def, only needed when S0
M569 P3 S0 ; Drive 3=e0; S1 = def, only needed when S0
M569 P5 S1 R1 T2.52:2.52:6.02:0.01 ; the external driver individual timing;
M569 P6 S1 R1 T2.52:2.52:6.02:0.01 ; the external driver individual timing;
;
M584 X5 Y6 Z2 E3 ; drive mapping - better to USE IT ONLY ONCE, since additional use will not overwrite older definitions...
; M350 MUST BE later then any M584!
M350 Z16 I1 ; Config (micro)stepping with(I1)without(I0) interpolation (trinamic microplyer provided only with *16-stepping)
M350 E16 I1 ; Config (micro)stepping with(I1)without(I0) interpolation (trinamic microplyer provided only with 16-stepping)
; leave x & y out since external
; z= 400 for fullstep, 40016=6400
; check out https://www.prusaprinters.org/calculator/ for some val-tweaking:
M92 X94.12 Y94.12 Z6400.00 E415.00 ; Set steps per mm corresponding to the before defined microstepping
; M92 ; M92 without parameters = Report current steps/mm (since M500 at end of this file saves recalced vals)
M566 X300.00 Y300.00 Z0.1 E120.00 ; Set maximum instantaneous speed changes (mm/min)
M203 X10000.00 Y10000.00 Z225.00 E1200.00 ; Set maximum speeds (mm/min)
M201 X200.00 Y200.00 Z1.00 E200.00 ; Set accelerations (mm/s^2)
M906 Z2400.00 E850.00 I25 ; Set motor currents (mA) and motor idle factor in per cent
M84 S5 Z E0 ; Set idle timeout with S in seconds, only for internal drives

Tytn

@lb
I have the same motors in a coreXY setup and noticed I was getting unexpected movement, redesigned the carriage 3 times to make it more rigid. I was assuming this was where my movement was coming from. Even with a all aluminum design I was still experiencing these movements. Then I noticed one motor was moving slightly more than the other.

The key for me was to increase the T parameter to T3.5:3.5:6:0

As soon as I did that everything ran smooth as butter, you can barely hear these things running. I am running 128 microstepping on the drives.

This slight movement may be whats throwing off your calculations!

I will double check my exact T config later if you need it, I am going off memory here but I am almost positive these are the amounts I had in. I know I had to increase them before everything ran smooth and accurately

Tytn

This post is deleted!

A Former User

@tytn
YUHUU: I OWE YOU A BEER! THAT WAS IT!!!
THANKS!
(Sh?%$§ datasheet with it´s >2.5val... - HA!)
Buttersmooth, almost cannot hear anything !
Since kinematics (just those optical-endstops need resistors with less ohm) works now I can jump over to start filament-templates! THANKS BOTH OF YOU!

Edit: could go down until 3.3, from 3.2 on it had the "old" behaviour; to have security margin instead of 3.3 I put 3.4 in the config.g...

Repeatability on both axis even with fast directionchanges <=0.01mm - I am so happy now!

Best regards

Tytn

@lb happy it worked for you.

A Former User

@tytn
@dc42

Question that came to my mind a few days later now:

If those motors are defined AFTER (in my case) the Z & E0 that use the internal TMC-drivers from the duet2, the "T3.4:3.4:6:0" for P5 & P6 do not "destroy" the values that are saved for Z & E0 internally that were without T? Just want to be sure, if I have to explicitly put/define T for the internal drives also as soon as an external drive is defined and what would be those values then...

Why am I asking:

The Gcode-website for M569: "RepRapFirmware only remembers the highest T parameters seen in any M569 command, and applies that value to all drivers for which any nonzero T parameter was specified"

?

dc42

The M569 T parameters default to zero, so they will be zero for the internal drivers assuming you don't change them.

A Former User

@dc42
Thanks!
Also thanks for your advise with the maximum obtainable speed related to the microsteppingamount -> Will shoot for something around 200-300 steps per mm then
Edit: Faster(more/higher) possible micro-stepping for external drives could be a cool feature for the new board you are cooking up, just sayin

dc42

@lb said in external driver "iHSS60" connection-question:

Edit: Faster(more/higher) possible micro-stepping for external drives could be a cool feature for the new board you are cooking up, just sayin

That's likely to be impossible. The step pulse length and step pulse interval needed by the external drivers limit the maximum step pulse frequency. Whereas for the internal drivers, we expect to see an increase in the maximum step pulse rate.

A Former User

@dc42
Ah - learned something. Thanks!