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  • MTTI
  • MTTI's Avatar
17 Feb 2025 08:16
Replied by MTTI on topic New and Working RTAI debs for 2.9

New and Working RTAI debs for 2.9

Category: Installing LinuxCNC

Thanks for this answer.

I would like to install RTAI due to the jitter in my setup, which is around 70k.
I'm using 4 stepper motors with encoders (closed loop) and a USC board from PICO.

Sometimes, though not very often, I get an "Unexpected realtime delay" message.
Do you think this could be related to the jitter amount?

I've tried every optimization I could find in the BIOS...
 
Just having a look at the PICO config, is the base thread used ? From a quick look nothing appears to attach to the base thread. Which would lead me to think that a simple RT_PREEMPT kernel would be suffice. The PICO board would seem to operate in a simialr way to a mesa 7i90 using the EPP protocol. IE using the parallel port to send timing info to a FPGA.


 

You're right, into the HAL file, there is only mention of servo-thread:
# Generated by stepconf 1.1 at Tue Jan 28 10:21:07 2025
# Si vous modifiez ce fichier, il sera
# écrasé quand vous relancerez Stepconf
loadrt [KINS]KINEMATICS

loadrt [EMCMOT]EMCMOT servo_period_nsec=[EMCMOT]SERVO_PERIOD num_joints=[KINS]JOINTS num_spindles=[TRAJ]SPINDLES

# next load the PID module, for four PID loops
loadrt pid num_chan=4

loadrt  plasmac

loadrt hal_ppmc epp_dir=1 

# make some signals for the scope for tuning.
loadrt ddt count=4
# add components for E-stop logic
loadrt estop_latch count=1
loadrt and2 count=1

# set up the realtime thread
# read inputs first
addf ppmc.0.read servo-thread
# then run the motion controller
addf motion-command-handler servo-thread
addf and2.0 servo-thread
addf estop-latch.0 servo-thread
addf motion-controller servo-thread
# then the PID loops
addf pid.0.do-pid-calcs servo-thread
addf pid.1.do-pid-calcs servo-thread
addf pid.2.do-pid-calcs servo-thread
addf pid.3.do-pid-calcs servo-thread
# write outputs last
addf ppmc.0.write servo-thread


# ---PLASMA INPUT DEBOUNCE---
loadrt dbounce names=db_breakaway,db_float,db_ohmic,db_arc-ok
addf db_float     servo-thread
addf db_ohmic     servo-thread
addf db_breakaway servo-thread
addf db_arc-ok    servo-thread

# ---JOINT ASSOCIATED WITH THE Z AXIS---
net plasmac:axis-position joint.2.pos-fb => plasmac.axis-z-position

# ---PLASMA INPUTS---
# ---all modes---
net plasmac:float-switch   => db_float.in
net plasmac:breakaway      => db_breakaway.in
net plasmac:ohmic-probe    => db_ohmic.in
net plasmac:ohmic-sense-in   => plasmac.ohmic-sense-in
# ---modes 0 & 1
net plasmac:arc-voltage-in => plasmac.arc-voltage-in
# ---modes 1 & 2
net plasmac:arc-ok-in      => db_arc-ok.in
# ---mode 2
net plasmac:move-up        => plasmac.move-up
net plasmac:move-down      => plasmac.move-down

# ---PLASMA OUTPUTS---
# ---all modes---
net plasmac:ohmic-enable   <= plasmac.ohmic-enable
net plasmac:scribe-arm     <= plasmac.scribe-arm
net plasmac:scribe-on      <= plasmac.scribe-on

# connect limit/home switch outputs to motion controller
net Xminlim <= ppmc.0.din.01.in
net Xminlim => joint.0.neg-lim-sw-in
net Xmaxlim <= ppmc.0.din.02.in
net Xmaxlim => joint.0.pos-lim-sw-in
net Xhome <= ppmc.0.din.00.in
net Xhome => joint.0.home-sw-in

net Yminlim <= ppmc.0.din.05.in
net Yminlim => joint.1.neg-lim-sw-in
net Ymaxlim <= ppmc.0.din.06.in
net Ymaxlim => joint.1.pos-lim-sw-in
net Yhome <= ppmc.0.din.04.in
net Yhome => joint.1.home-sw-in

net Zminlim <= ppmc.0.din.09.in
net Zminlim => joint.2.neg-lim-sw-in
net Zmaxlim <= ppmc.0.din.10.in
net Zmaxlim => joint.2.pos-lim-sw-in
net Zhome <= ppmc.0.din.08.in
net Zhome => joint.2.home-sw-in

net Aminlim <= ppmc.0.din.12.in
net Aminlim => joint.3.neg-lim-sw-in
net Amaxlim <= ppmc.0.din.13.in
net Amaxlim => joint.3.pos-lim-sw-in
net Ahome <= ppmc.0.din.11.in
net Ahome => joint.3.home-sw-in


# connect index pulses to motion controller
# uncomment these lines only if you have a Rev 2 USC board
# newsig Xindex bit
# newsig Yindex  bit
# newsig Zindex bit
# newsig Aindex bit
# linksp Xindex <= ppmc.0.encoder.00.index-enable
# linksp Xindex => joint.0.index-enable
# linksp Yindex <= ppmc.0.encoder.01.index-enable
# linksp Yindex => joint.1.index-enable
# linksp Zindex <= ppmc.0.encoder.02.index-enable
# linksp Zindex => joint.2.index-enable
# linksp Aindex <= ppmc.0.encoder.03.index-enable
# linksp Aindex => joint.3.index-enable

#
# Connect I/O controller I/Os
#

# connect e-stop write/sense to I/O controller
# and univstep's fault with estop's output, so  estop FF is reset, but
#      prevent continued estop signal from univstep from holding FF cleared
net ppmcEstop ppmc.0.din.15.in-not
net ppmcEstop and2.0.in0
net EstopOkIn estop-latch.0.fault-in
net EstopOkIn and2.0.out
net EstopOkOut <= ppmc.0.dout.07.out
net EstopOkOut iocontrol.0.emc-enable-in
net EstopOkOut estop-latch.0.ok-out
net EstopOkOut and2.0.in1
net emc-estop-out iocontrol.0.user-enable-out
net emc-estop-out estop-latch.0.ok-in
net emc-estop-reset iocontrol.0.user-request-enable
net emc-estop-reset estop-latch.0.reset

net emc-estop-out estop-latch.0.ok-in 

# connect spindle fwd/rev to I/O controller
net SpindleFwd <= ppmc.0.dout.00.out
net SpindleFwd => spindle.0.forward
net SpindleRev <= ppmc.0.dout.01.out
net SpindleRev => spindle.0.reverse

# connect spindle brake to I/O controller
net SpindleBrakeOn <= ppmc.0.dout.02.out
net SpindleBrakeOn => spindle.0.brake

# connect mist/flood coolant to I/O controller
net MistOn <= ppmc.0.dout.03.out
net MistOn => iocontrol.0.coolant-mist
net FloodOn <= ppmc.0.dout.04.out
net FloodOn => iocontrol.0.coolant-flood


# connect position feedback signals to encoders
net Xpos-fb <= ppmc.0.encoder.00.position
net Ypos-fb <= ppmc.0.encoder.01.position
net Zpos-fb <= ppmc.0.encoder.02.position
net Apos-fb <= ppmc.0.encoder.03.position

# get feedback scaling from ini file
setp ppmc.0.encoder.00.scale [JOINT_0]INPUT_SCALE
setp ppmc.0.encoder.01.scale [JOINT_1]INPUT_SCALE
setp ppmc.0.encoder.02.scale [JOINT_2]INPUT_SCALE
setp ppmc.0.encoder.03.scale [JOINT_3]INPUT_SCALE

# connect PID output signals to step generators
net Xoutput => ppmc.0.stepgen.00.velocity
net Youtput => ppmc.0.stepgen.01.velocity
net Zoutput => ppmc.0.stepgen.02.velocity
net Aoutput => ppmc.0.stepgen.03.velocity

# connect axis enables to step generators
net Xenable => ppmc.0.stepgen.00.enable
net Yenable => ppmc.0.stepgen.01.enable
net Zenable => ppmc.0.stepgen.02.enable
net Aenable => ppmc.0.stepgen.03.enable

# set output scaling from ini file
# input and output scales should (normally) be the same for a USC
setp ppmc.0.stepgen.00.scale [JOINT_0]OUTPUT_SCALE
setp ppmc.0.stepgen.01.scale [JOINT_1]OUTPUT_SCALE
setp ppmc.0.stepgen.02.scale [JOINT_2]OUTPUT_SCALE
setp ppmc.0.stepgen.03.scale [JOINT_3]OUTPUT_SCALE

# add a couple of tuning test links
# if these are useful will want to add them to the other axes as well
# or make these setup with the tuning script
# net Xoutput ddt.0.in
# net Xpos-fb ddt.1.in


# HAL config file for servos -- expanded from core_servo.hal
# for a full four axis setup

# create four position feedback signals

# connect position feedback to PID loop
net Xpos-fb => pid.0.feedback
net Ypos-fb => pid.1.feedback
net Zpos-fb => pid.2.feedback
net Apos-fb => pid.3.feedback

# connect position feedback to motion module
net Xpos-fb => joint.0.motor-pos-fb
net Ypos-fb => joint.1.motor-pos-fb
net Zpos-fb => joint.2.motor-pos-fb
net Apos-fb => joint.3.motor-pos-fb

# create PID to DAC output signals

# connect output signals to output of PID loops
net Xoutput <= pid.0.output
net Youtput <= pid.1.output
net Zoutput <= pid.2.output
net Aoutput <= pid.3.output

# set PID loop output limits to +/-1.00
setp pid.0.maxoutput [JOINT_0]PID_MAX_VEL
setp pid.1.maxoutput [JOINT_1]PID_MAX_VEL
setp pid.2.maxoutput [JOINT_2]PID_MAX_VEL
setp pid.3.maxoutput [JOINT_3]PID_MAX_VEL

# set PID loop gains
setp pid.0.Pgain [JOINT_0]P
setp pid.0.Igain [JOINT_0]I
setp pid.0.Dgain [JOINT_0]D
setp pid.0.bias [JOINT_0]BIAS
setp pid.0.FF0 [JOINT_0]FF0
setp pid.0.FF1 [JOINT_0]FF1
setp pid.0.FF2 [JOINT_0]FF2
setp pid.0.deadband [JOINT_0]DEADBAND

setp pid.1.Pgain [JOINT_1]P
setp pid.1.Igain [JOINT_1]I
setp pid.1.Dgain [JOINT_1]D
setp pid.1.bias [JOINT_1]BIAS
setp pid.1.FF0 [JOINT_1]FF0
setp pid.1.FF1 [JOINT_1]FF1
setp pid.1.FF2 [JOINT_1]FF2
setp pid.1.deadband [JOINT_1]DEADBAND

setp pid.2.Pgain [JOINT_2]P
setp pid.2.Igain [JOINT_2]I
setp pid.2.Dgain [JOINT_2]D
setp pid.2.bias [JOINT_2]BIAS
setp pid.2.FF0 [JOINT_2]FF0
setp pid.2.FF1 [JOINT_2]FF1
setp pid.2.FF2 [JOINT_2]FF2
setp pid.2.deadband [JOINT_2]DEADBAND

setp pid.3.Pgain [JOINT_3]P
setp pid.3.Igain [JOINT_3]I
setp pid.3.Dgain [JOINT_3]D
setp pid.3.bias [JOINT_3]BIAS
setp pid.3.FF0 [JOINT_3]FF0
setp pid.3.FF1 [JOINT_3]FF1
setp pid.3.FF2 [JOINT_3]FF2
setp pid.3.deadband [JOINT_3]DEADBAND

# create four position command signals

# connect position commands to motion controller
net Xpos-cmd <= joint.0.motor-pos-cmd
net Ypos-cmd <= joint.1.motor-pos-cmd
net Zpos-cmd <= joint.2.motor-pos-cmd
net Apos-cmd <= joint.3.motor-pos-cmd

# connect position commands to PID input
net Xpos-cmd => pid.0.command
net Ypos-cmd => pid.1.command
net Zpos-cmd => pid.2.command
net Apos-cmd => pid.3.command

# create bit signals to enable/disable the PID loops

# connect the signals to the motion controller
net Xenable <= joint.0.amp-enable-out
net Yenable <= joint.1.amp-enable-out
net Zenable <= joint.2.amp-enable-out
net Aenable <= joint.3.amp-enable-out

# connect the signals to the PID blocks
net Xenable => pid.0.enable
net Yenable => pid.1.enable
net Zenable => pid.2.enable
net Aenable => pid.3.enable

But i'm not an expert in this type of configuration...
  • Aciera
  • Aciera's Avatar
17 Feb 2025 08:01
Replied by Aciera on topic 3D plot: Cannot probe with zero feedrate

3D plot: Cannot probe with zero feedrate

Category: General LinuxCNC Questions

The issue is caused by the part with the g38 command as that is where the error message comes from. So you would only call 'tool_touch_off.ngc' when #<_task> EQ 1
  • MTTI
  • MTTI's Avatar
17 Feb 2025 07:51
Replied by MTTI on topic New and Working RTAI debs for 2.9

New and Working RTAI debs for 2.9

Category: Installing LinuxCNC

Are you hitting 70K microseconds on RTAI or PREEMPT_RT?

Just in case, here are the options I've found to help:

github.com/NTULINUX/RTAI/blob/master/README.BIOS

I only hit 70k jitter occasionally and only when the CPU usage is high, for example when running multiples GLXGEARS, playing HD videos on YouTube... Otherwise, my jitter stays around 50k.

I'm using PREEMPT_RT because RTAI doesn't work at all, even the latency test freezes the computer.

Thanks for the link, I already found it along with many others. 
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