spindle feedback and latency issues

Hello everyone,
i built a cnc lathe out of a 7x12 benchtop lathe, it ran with Mach3 - but i wasnt able to cut extra fine threads with it. (had 2 pitches instead the expected 1) normal threads (pitch >1mm) worked like a charm
So i decided to take a look on LinuxCNC. As a Click&Error master, setup was quite easy, i'm running it on a HP Compaq 6700 P4(HT disabled) and gettin <40.000 Jitter
Had my backlashenabled X axis ballscrew G0-ing around half an hour with no lost steps. (1/8 microstepping)
i also did the SMI trick as figured in the wiki, but it doesnt load, guess my chipset does not support it
But everytime at startup, the programm tells me latency isnt alright and i should check it - what does that mean?

Also i cant manage to get spindle feedback working..
i do have a spindle index card (cnc4pc C3), optoisolated, single slot disc and a working signal at HAL (spindle index= true, false)
Wiki says i need to configure "encoder phase a" and "index pulse"
When assigning the "encoder phase a" in the stepconf wizard, im able to give a value for "steps per rev" but linuxcnc wont load my machine then and aborts

What am i doing wrong? I just have 1 Input signal to handle spindle feedback for feed per rev. and threading..

i hope someone may can help me

Hello,

For a start,

You might want to review this...
www.linuxcnc.org/docs/2.4/html/config_stepconf.html#r1_1

and

wiki.linuxcnc.org/cgi-bin/wiki.pl?TroubleShooting

Run your latency test for an extended period of time while using some graphic programs, drag windows around and such.
Use the resulting numbers to run Stepconfig again to make sure you are not trying to run faster than your computer is capable of.

Rick G

i redid the stepconf and entered a higher jitter, 50535
thats what latency-test shows me after 15min of 2x glxgears and some surfin arround with firefox

when starting a programm jitter raises up to 1million, is that normal? i resettet latency-test after loading my programms and let it run from that on - giving a base 50535 and servo 25304


in stepconf i picked Encoder Phase A instead of Index Pulse and linuxCNC just wont start now.

My device is in the Supported Hardware section of the wiki:

HP DC7600
P4 3Ghz 4GB RAM, On board video, Ubuntu 10.04 LTS installed from LiveCD?, HT Disabled in BIOS, 2x glxgears running, snd kernel modules disables, SMI disabled

i dont know where to disable kernel modules, and the SMI modification doesnt work here


How do i solve the PYVCP thing?

It looks like it might be worth turnign off hyperthreading in the BIOS.
I am not sure what you mean about "SMI not working here"
If it is a problem with opening files then perhaps there is something funny with the HDD.
It might be interesting to try opening a file from a USB stick to see if there is a problem then.
This thread might be interesting www.linuxcnc.org/index.php/french/forum/...ne-hard-drive-access
Though all it really says is that IDE drives might be bad.

I allready disabled HT in the Bios, gave a huge boost (down ofc) while double glxgear
I'll borrow me an usb stick to test this
I followed the wiki guide to load the SMI module with linuxcnc, but it doesn't load

If it worked before, then it sounds like you missed something out in stepconf. Or stepconf got too clever and decided you don't have a spindle encoder any more and didn't put the gauge in. If you look in the INI file do you see a PYVCP= entry?

yes, there is a entry

I had no programm to run from the usb stick, so i tried opening a .mp3 from hdd and usbdrive
loading the mp3 made no difference (RTAI latency test), but opening the stock ubuntu 12.04 player caused every time a +3 overrun and latency max up to 108.000
Latency Average (RTAI latency test) is allways a negative amount
at the HDD Read test, my SATAII HDD had a accesstime of 14.6ms (retailer datasheed=9ms)
Memtest86+ was just fine, 2x1024mb modules synch dualchannel
P4 Hyperthreading off, all BIOS features look like recommended in the wiki
Nvidia 7100GS+, PCI-E, tried with and without the ubuntu-recommendet driver, no difference - Programms never load "smooth" aswell scrolling in firefox

I'm gonna buy me a SSD today, hope this solves it... i want to stop banging my head to the table...

You might try 8.04 instead of 10.04 and running the latency test again, often 8.04 will give better results depending on the hardware.

Rick G