Fake encoder index for simulation

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08 Jun 2023 21:32 #273218 by drummond
I got around to trying this, with little hope for success because I'm currently running the lathe spindle with a stepper motor in velocity mode and I wasn't sure how I might integrate stepperspindle.

I'm using 2.8.4 on an RPI4 with 7C81

It was an interesting exercise getting Halcompile to work, but I learned that raspbian responds to a right click on a file with a menu that includes "copy path(s)", click on that and you can paste the complete path into a terminal.

Once I had the comp file compiled and installed, I added the HAL entries as originally shown along with the amendments suggested by GaryLa

I loaded linuxcnc from a terminal (it's easier to find errors this way)  it didn't finish loading but:

./turner.hal:207: Pin 'stepperspindle.0.revs' does not exist

line 207 read: net spindle-pos stepperspindle.0.revs motion.spindle.0.revs
commenting it out resulted in linuxcnc loading without error.

a look at halshow pins under stepperspindle then 0 showed no pin with that name, but there was a very similar stepperspindle.0.spindle-revs and subbing this in resulted in that error going away, but

./turner.hal:207: Pin 'motion.spindle.0.revs' does not exist

Rinse and repeat finds we just need spindle.0.revs without the 'motion'

Now it loads without error.

Does it work, well that's a story for another day

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08 Jun 2023 22:24 - 09 Jun 2023 14:34 #273220 by PCW
Note that you can use index with step/dir driven spindles
with LinuxCNC 2.9 and Mesa cards with the correct firmware.
This allows spindle synchronized moves without an encoder,
though an index input is still required.

 
Last edit: 09 Jun 2023 14:34 by PCW. Reason: clarify

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09 Jun 2023 13:08 #273237 by andypugh

./turner.hal:207: Pin 'motion.spindle.0.revs' does not exist

Sorry, that was an error on my part, I typoed the older pin name by accident (now fixed in the original post) 

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09 Jun 2023 21:17 #273251 by drummond
When I look at HAL configuration there are four pins associated with Stepperspindle: index-enable, rawcounts, spindle-revs, time.

I'm running the lathe motor with the following in the ini file:

MOTOR_SCALE 3200 // stepper takes 3200 steps per revolution
STEP_SCALE  1600 // lathe spindle has a 2:1 relationship with the motor, stepper revolves once, lathe spindle revolves twice.

I wondered how this might gel with:

setp stepperspindle.0.steps-per-rev 1600

Which went in HAL file per the original instructions, it seems correct- but how could I be so lucky?

Got the motor running and watched the first 3 pins.

Results:

index-enable=nothing
rawcounts=count is going but with a minus sign in front of it
spindle-revs=count is going but with a minus sign in front of it

I can "correct" the minus on spindle revs by changing the HAL entry to:

setp stepperspindle.0.steps-per-rev -1600, which feels wrong somehow because the originals in the ini file are both positive and produce counterclockwise rotation with M4

rawcounts seems less trivial to fix

from the comp file:

.......signed steps-per-rev = 100 "stepper steps per rev / per index";

If that means what I think it means it will produce indexes far more frequently than I was expecting?

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10 Jun 2023 11:06 #273266 by andypugh
Negative scales are not unusual to reverse specific functions.
Counts being negative is not a problem for the fake index comp.
But I suspect that you might have a misconfiguration if M4 is normal rotation unless this is a back-tool lathe.

Looking down the spindle towards the tailstock, M3 should be clockwise and count up.

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10 Jun 2023 16:16 #273273 by drummond
Well, that was a typo combined with an interruption leading to an incomplete message being sent (!) Sorry about that

What it should have read is: "the originals in the ini file  are NOW both positive and produce counterclockwise motion with M3, to correct this I have to set them both back to negative

I could never get to watch the index changing by watching it on HAL configuration even with a spindle speed of 1 rpm (stepper running at 0.5 rpm)

I tried a simple g33 routine "in air" and everything seems to work, spindle synchronized motion without an encoder.  Thank you.

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