General questions on best method for installing Linuxcnc for software stepping.

Thanks for the help Tommy and Todd. I found that my latency dropped to 5us when I turned on polling and I stopped there. I have finished hooking up the limit switches, coolant switch and spindle communication via rs485. Now to try and decipher how to get axis to talk to the spindle(wj200). I can enable and disable the drive using hal configuration window. But I cannot get set either a frequency or a rpm and this is just using command line I need to work on getting connected to the ui and or gcode control.

Unless I misunderstand things, isolcpus doesn't turn off cores, it hides a core from the OS as a whole and lets the realtime system claim it to itself. So on a quad-core the OS thinks it is a 3-core system and uses those, and then the realtime system gets a dedicated core.

using isolcpus in any combination would give me a jitter of ~10 to 12 us for 99.99% of the time but every couple of minutes or so i would still get a large 30 to 40 us spike. So I turned off isolcpus completely and turned on polling and I now get a consistent 1 to 2 us jitter with occasional peaks of 5 to 6 us which is plenty fast.
The current configuration is awesome. Spindle control is down to the .1Hz with no hunting much better than using the pwm to analog method. rs485 and modbus for the win!!! estop and pause happen near instantaneously unlike tinyg2 which had to wait for the 32 move buffer to empty. no noise or lost steps. coolant is a little finicky because the pin toggles on startup so I get a short air blast every time I start linuxcnc. now need to learn about probing and hopefully mapping so that I can correct for the small amount of backlash and skew that my machine has. I think that my next step is to learn about gantrykins.c I tried using millkins.c to account for skew but couldn't get it to load with the latest dev version, I got it to compile though.

So I turned off isolcpus completely and turned on polling and I now get a consistent 1 to 2 us jitter with occasional peaks of 5 to 6 us which is plenty fast.

Could you explain where this setting is? I'm still coming to grips with Linux.

Yeah I get you there I am a beginner when it comes to Linux as well basically there was a script that I used ( I think I found it in a forum post) in order to set the RTAI kernel boot paramiters because if you did it manually you would need to change 2 separate files. In a few hours when I get back to the machine I'll post the script.

MDM3D wrote: I think that my next step is to learn about gantrykins.c I tried using millkins.c to account for skew but couldn't get it to load with the latest dev version, I got it to compile though.

If you are using the latest dev version then gantrykins doesn't exist any more. The same functionality is included in trivkins.

There is an example of what a gantry config with trivkins should look like here, look particularly in the [KINS] section of the INI
github.com/LinuxCNC/linuxcnc/blob/master.../sim/axis/gantry.ini