Pesky "following error"s with Mesa 7c81

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10 Apr 2023 16:15 #268760 by TallGuy
Sorry, I hoped to resolve this issue myself but I can't seem to get to grips with it.

I've converted an SX2P with Pi4, Mesa 7c81 and an eBay 5 axis Bob, feeding motor controllers and steppers from cnc4you.co.uk.

I keep getting the infamous "following errors" on all joints. I have wondered if this is because pncconf sets things up for servos rather than steppers?
The errors can come very quickly, sometimes when the head is stationary, or it can lull me into a false sense of security and take a while to pop up.
I also experience watchdog errors sometimes.

Linux 5,4.83-rt48-v71+, LinuxCNC 2.8.4 

I've obviously for something or some things very wrong but I'm stuck :/

Thanks in advance for your help!
# Generated by PNCconf at Sun Jan  8 17:08:56 2023
# Using LinuxCNC version:  2.8
# If you make changes to this file, they will be
# overwritten when you run PNCconf again

[EMC]
MACHINE = Milling_machine
DEBUG = 0
VERSION = 1.1

[DISPLAY]
DISPLAY = axis
POSITION_OFFSET = RELATIVE
POSITION_FEEDBACK = ACTUAL
MAX_FEED_OVERRIDE = 2.000000
MAX_SPINDLE_OVERRIDE = 1.000000
MIN_SPINDLE_OVERRIDE = 0.500000
INTRO_GRAPHIC = linuxcnc.gif
INTRO_TIME = 5
PROGRAM_PREFIX = /mnt/filestore
INCREMENTS = 5mm 1mm .5mm .1mm .05mm .01mm .005mm
POSITION_FEEDBACK = ACTUAL
DEFAULT_LINEAR_VELOCITY = 6.000000
MAX_LINEAR_VELOCITY = 25.000000
MIN_LINEAR_VELOCITY = 0.500000
DEFAULT_ANGULAR_VELOCITY = 12.000000
MAX_ANGULAR_VELOCITY = 180.000000
MIN_ANGULAR_VELOCITY = 1.666667
EDITOR = gedit
GEOMETRY = xyz

[FILTER]
PROGRAM_EXTENSION = .png,.gif,.jpg Greyscale Depth Image
PROGRAM_EXTENSION = .py Python Script
png = image-to-gcode
gif = image-to-gcode
jpg = image-to-gcode
py = python

[TASK]
TASK = milltask
CYCLE_TIME = 0.010

[RS274NGC]
PARAMETER_FILE = linuxcnc.var
RS274NGC_STARTUP_CODE = G21 G40 G90 G94 G97 G64 P0.025

[EMCMOT]
EMCMOT = motmod
COMM_TIMEOUT = 1.0
SERVO_PERIOD = 1000000

[HMOT]
CARD0=hm2_7c81.0

[HAL]
HALUI = halui
HALFILE = Milling_machine.hal
HALFILE = custom.hal
POSTGUI_HALFILE = postgui_call_list.hal
SHUTDOWN = shutdown.hal

[HALUI]

[KINS]
JOINTS = 3
KINEMATICS = trivkins coordinates=XYZ

[TRAJ]
COORDINATES =  XYZ
LINEAR_UNITS = mm
ANGULAR_UNITS = degree
DEFAULT_LINEAR_VELOCITY = 2.50
MAX_LINEAR_VELOCITY = 25.00
NO_FORCE_HOMING = 1

[EMCIO]
EMCIO = io
CYCLE_TIME = 0.100
TOOL_TABLE = tool.tbl
TOOL_CHANGE_QUILL_UP = 1

#******************************************
[AXIS_X]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -0.01
MAX_LIMIT = 200.0

[JOINT_0]
TYPE = LINEAR
HOME = 0.0
FERROR = 10.0
MIN_FERROR = 1.0
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 31.25
STEPGEN_MAXACCEL = 937.5
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP   = 10000
DIRHOLD    = 10000
STEPLEN    = 5000
STEPSPACE  = 5000
STEP_SCALE=500
MIN_LIMIT = -0.01
MAX_LIMIT = 200.0
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = -1.000000
HOME_LATCH_VEL = -0.500000
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = NO
HOME_SEQUENCE = 1
#******************************************

#******************************************
[AXIS_Y]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -0.01
MAX_LIMIT = 200.0

[JOINT_1]
TYPE = LINEAR
HOME = 0.0
FERROR = 10.0
MIN_FERROR = 1.0
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 31.25
STEPGEN_MAXACCEL = 937.5
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP   = 10000
DIRHOLD    = 10000
STEPLEN    = 5000
STEPSPACE  = 5000
STEP_SCALE=-500
MIN_LIMIT = -0.01
MAX_LIMIT = 200.0
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = -1.000000
HOME_LATCH_VEL = -0.500000
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = NO
HOME_SEQUENCE = 2
#******************************************

#******************************************
[AXIS_Z]
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
MIN_LIMIT = -100.0
MAX_LIMIT = 0.01

[JOINT_2]
TYPE = LINEAR
HOME = 0.0
FERROR = 10.0
MIN_FERROR = 1.0
MAX_VELOCITY = 25.0
MAX_ACCELERATION = 750.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 31.25
STEPGEN_MAXACCEL = 937.5
P = 1000.0
I = 0.0
D = 0.0
FF0 = 0.0
FF1 = 1.0
FF2 = 0.0
BIAS = 0.0
DEADBAND = 0.0
MAX_OUTPUT = 0.0
# these are in nanoseconds
DIRSETUP   = 10000
DIRHOLD    = 10000
STEPLEN    = 5000
STEPSPACE  = 5000
# STEP_SCALE = 100.0
STEP_SCALE=1000.0
MIN_LIMIT = -100.0
MAX_LIMIT = 0.01
HOME_OFFSET = 0.000000
HOME_SEARCH_VEL = -1.000000
HOME_LATCH_VEL = -0.500000
HOME_FINAL_VEL = 0.000000
HOME_USE_INDEX = NO
HOME_SEQUENCE = 0
#******************************************
 
# Generated by PNCconf at Sun Jan  8 17:08:56 2023
# Using LinuxCNC version:  2.8
# If you make changes to this file, they will be
# overwritten when you run PNCconf again

loadrt [KINS]KINEMATICS
loadrt [EMCMOT]EMCMOT servo_period_nsec=[EMCMOT]SERVO_PERIOD num_joints=[KINS]JOINTS
loadrt hostmot2
loadrt hm2_rpspi config="num_encoders=0 num_pwmgens=1 num_stepgens=5" 
setp    [HMOT](CARD0).pwmgen.pwm_frequency 20000
setp    [HMOT](CARD0).pwmgen.pdm_frequency 6000000
setp    [HMOT](CARD0).watchdog.timeout_ns 10000000
loadrt pid names=pid.x,pid.y,pid.z,pid.s

addf [HMOT](CARD0).read          servo-thread
addf motion-command-handler   servo-thread
addf motion-controller        servo-thread
addf pid.x.do-pid-calcs       servo-thread
addf pid.y.do-pid-calcs       servo-thread
addf pid.z.do-pid-calcs       servo-thread
addf pid.s.do-pid-calcs       servo-thread
addf [HMOT](CARD0).write         servo-thread

# ---Chargepump StepGen: 0.25 velocity = 10Khz square wave output---

setp   [HMOT](CARD0).stepgen.04.dirsetup        100
setp   [HMOT](CARD0).stepgen.04.dirhold         100
setp   [HMOT](CARD0).stepgen.04.steplen         100
setp   [HMOT](CARD0).stepgen.04.stepspace       100
setp   [HMOT](CARD0).stepgen.04.position-scale  10000
setp   [HMOT](CARD0).stepgen.04.step_type       2
setp   [HMOT](CARD0).stepgen.04.control-type    1
setp   [HMOT](CARD0).stepgen.04.maxaccel        0
setp   [HMOT](CARD0).stepgen.04.maxvel          0
setp   [HMOT](CARD0).stepgen.04.velocity-cmd    0.25

net x-enable                                 => [HMOT](CARD0).stepgen.04.enable

# external output signals

# external input signals

# --- HOME-X ---
net home-x     <=  [HMOT](CARD0).gpio.013.in

# --- HOME-Y ---
net home-y     <=  [HMOT](CARD0).gpio.014.in

# --- HOME-Z ---
net home-z     <=  [HMOT](CARD0).gpio.015.in

#*******************
#  AXIS X JOINT 0
#*******************

setp   pid.x.Pgain     [JOINT_0]P
setp   pid.x.Igain     [JOINT_0]I
setp   pid.x.Dgain     [JOINT_0]D
setp   pid.x.bias      [JOINT_0]BIAS
setp   pid.x.FF0       [JOINT_0]FF0
setp   pid.x.FF1       [JOINT_0]FF1
setp   pid.x.FF2       [JOINT_0]FF2
setp   pid.x.deadband  [JOINT_0]DEADBAND
setp   pid.x.maxoutput [JOINT_0]MAX_OUTPUT
setp   pid.x.error-previous-target true
# This setting is to limit bogus stepgen
# velocity corrections caused by position
# feedback sample time jitter.
setp   pid.x.maxerror 0.012700

net x-index-enable  => pid.x.index-enable
net x-enable        =>  pid.x.enable
net x-pos-cmd       =>  pid.x.command
net x-pos-fb        =>  pid.x.feedback
net x-output        <=  pid.x.output

# Step Gen signals/setup

setp   [HMOT](CARD0).stepgen.00.dirsetup        [JOINT_0]DIRSETUP
setp   [HMOT](CARD0).stepgen.00.dirhold         [JOINT_0]DIRHOLD
setp   [HMOT](CARD0).stepgen.00.steplen         [JOINT_0]STEPLEN
setp   [HMOT](CARD0).stepgen.00.stepspace       [JOINT_0]STEPSPACE
setp   [HMOT](CARD0).stepgen.00.position-scale  [JOINT_0]STEP_SCALE
setp   [HMOT](CARD0).stepgen.00.step_type        0
setp   [HMOT](CARD0).stepgen.00.control-type     1
setp   [HMOT](CARD0).stepgen.00.maxaccel         [JOINT_0]STEPGEN_MAXACCEL
setp   [HMOT](CARD0).stepgen.00.maxvel           [JOINT_0]STEPGEN_MAXVEL

# ---closedloop stepper signals---

net x-pos-cmd    <= joint.0.motor-pos-cmd
net x-vel-cmd    <= joint.0.vel-cmd
net x-output     => [HMOT](CARD0).stepgen.00.velocity-cmd
net x-pos-fb     <= [HMOT](CARD0).stepgen.00.position-fb
net x-pos-fb     => joint.0.motor-pos-fb
net x-enable     <= joint.0.amp-enable-out
net x-enable     => [HMOT](CARD0).stepgen.00.enable

# ---setup home / limit switch signals---

net home-x     =>  joint.0.home-sw-in
net x-neg-limit     =>  joint.0.neg-lim-sw-in
net x-pos-limit     =>  joint.0.pos-lim-sw-in

#*******************
#  AXIS Y JOINT 1
#*******************

setp   pid.y.Pgain     [JOINT_1]P
setp   pid.y.Igain     [JOINT_1]I
setp   pid.y.Dgain     [JOINT_1]D
setp   pid.y.bias      [JOINT_1]BIAS
setp   pid.y.FF0       [JOINT_1]FF0
setp   pid.y.FF1       [JOINT_1]FF1
setp   pid.y.FF2       [JOINT_1]FF2
setp   pid.y.deadband  [JOINT_1]DEADBAND
setp   pid.y.maxoutput [JOINT_1]MAX_OUTPUT
setp   pid.y.error-previous-target true
# This setting is to limit bogus stepgen
# velocity corrections caused by position
# feedback sample time jitter.
setp   pid.y.maxerror 0.012700

net y-index-enable  => pid.y.index-enable
net y-enable        =>  pid.y.enable
net y-pos-cmd       =>  pid.y.command
net y-pos-fb        =>  pid.y.feedback
net y-output        <=  pid.y.output

# Step Gen signals/setup

setp   [HMOT](CARD0).stepgen.01.dirsetup        [JOINT_1]DIRSETUP
setp   [HMOT](CARD0).stepgen.01.dirhold         [JOINT_1]DIRHOLD
setp   [HMOT](CARD0).stepgen.01.steplen         [JOINT_1]STEPLEN
setp   [HMOT](CARD0).stepgen.01.stepspace       [JOINT_1]STEPSPACE
setp   [HMOT](CARD0).stepgen.01.position-scale  [JOINT_1]STEP_SCALE
setp   [HMOT](CARD0).stepgen.01.step_type        0
setp   [HMOT](CARD0).stepgen.01.control-type     1
setp   [HMOT](CARD0).stepgen.01.maxaccel         [JOINT_1]STEPGEN_MAXACCEL
setp   [HMOT](CARD0).stepgen.01.maxvel           [JOINT_1]STEPGEN_MAXVEL

# ---closedloop stepper signals---

net y-pos-cmd    <= joint.1.motor-pos-cmd
net y-vel-cmd    <= joint.1.vel-cmd
net y-output     => [HMOT](CARD0).stepgen.01.velocity-cmd
net y-pos-fb     <= [HMOT](CARD0).stepgen.01.position-fb
net y-pos-fb     => joint.1.motor-pos-fb
net y-enable     <= joint.1.amp-enable-out
net y-enable     => [HMOT](CARD0).stepgen.01.enable

# ---setup home / limit switch signals---

net home-y     =>  joint.1.home-sw-in
net y-neg-limit     =>  joint.1.neg-lim-sw-in
net y-pos-limit     =>  joint.1.pos-lim-sw-in

#*******************
#  AXIS Z JOINT 2
#*******************

setp   pid.z.Pgain     [JOINT_2]P
setp   pid.z.Igain     [JOINT_2]I
setp   pid.z.Dgain     [JOINT_2]D
setp   pid.z.bias      [JOINT_2]BIAS
setp   pid.z.FF0       [JOINT_2]FF0
setp   pid.z.FF1       [JOINT_2]FF1
setp   pid.z.FF2       [JOINT_2]FF2
setp   pid.z.deadband  [JOINT_2]DEADBAND
setp   pid.z.maxoutput [JOINT_2]MAX_OUTPUT
setp   pid.z.error-previous-target true
# This setting is to limit bogus stepgen
# velocity corrections caused by position
# feedback sample time jitter.
setp   pid.z.maxerror 0.012700

net z-index-enable  => pid.z.index-enable
net z-enable        =>  pid.z.enable
net z-pos-cmd       =>  pid.z.command
net z-pos-fb        =>  pid.z.feedback
net z-output        <=  pid.z.output

# Step Gen signals/setup

setp   [HMOT](CARD0).stepgen.02.dirsetup        [JOINT_2]DIRSETUP
setp   [HMOT](CARD0).stepgen.02.dirhold         [JOINT_2]DIRHOLD
setp   [HMOT](CARD0).stepgen.02.steplen         [JOINT_2]STEPLEN
setp   [HMOT](CARD0).stepgen.02.stepspace       [JOINT_2]STEPSPACE
setp   [HMOT](CARD0).stepgen.02.position-scale  [JOINT_2]STEP_SCALE
setp   [HMOT](CARD0).stepgen.02.step_type        0
setp   [HMOT](CARD0).stepgen.02.control-type     1
setp   [HMOT](CARD0).stepgen.02.maxaccel         [JOINT_2]STEPGEN_MAXACCEL
setp   [HMOT](CARD0).stepgen.02.maxvel           [JOINT_2]STEPGEN_MAXVEL

# ---closedloop stepper signals---

net z-pos-cmd    <= joint.2.motor-pos-cmd
net z-vel-cmd    <= joint.2.vel-cmd
net z-output     => [HMOT](CARD0).stepgen.02.velocity-cmd
net z-pos-fb     <= [HMOT](CARD0).stepgen.02.position-fb
net z-pos-fb     => joint.2.motor-pos-fb
net z-enable     <= joint.2.amp-enable-out
net z-enable     => [HMOT](CARD0).stepgen.02.enable

# ---setup home / limit switch signals---

net home-z     =>  joint.2.home-sw-in
net z-neg-limit     =>  joint.2.neg-lim-sw-in
net z-pos-limit     =>  joint.2.pos-lim-sw-in


#******************************
# connect miscellaneous signals
#******************************

#  ---HALUI signals---

net axis-select-x  halui.axis.x.select
net jog-x-pos      halui.axis.x.plus
net jog-x-neg      halui.axis.x.minus
net jog-x-analog   halui.axis.x.analog
net x-is-homed     halui.joint.0.is-homed
net axis-select-y  halui.axis.y.select
net jog-y-pos      halui.axis.y.plus
net jog-y-neg      halui.axis.y.minus
net jog-y-analog   halui.axis.y.analog
net y-is-homed     halui.joint.1.is-homed
net axis-select-z  halui.axis.z.select
net jog-z-pos      halui.axis.z.plus
net jog-z-neg      halui.axis.z.minus
net jog-z-analog   halui.axis.z.analog
net z-is-homed     halui.joint.2.is-homed
net jog-selected-pos      halui.axis.selected.plus
net jog-selected-neg      halui.axis.selected.minus
net spindle-manual-cw     halui.spindle.0.forward
net spindle-manual-ccw    halui.spindle.0.reverse
net spindle-manual-stop   halui.spindle.0.stop
net machine-is-on         halui.machine.is-on
net jog-speed             halui.axis.jog-speed
net MDI-mode              halui.mode.is-mdi

#  ---coolant signals---

net coolant-mist      <=  iocontrol.0.coolant-mist
net coolant-flood     <=  iocontrol.0.coolant-flood

#  ---probe signal---

net probe-in     =>  motion.probe-input

#  ---motion control signals---

net in-position               <=  motion.in-position
net machine-is-enabled        <=  motion.motion-enabled

#  ---digital in / out signals---

#  ---estop signals---

net estop-out     <=  iocontrol.0.user-enable-out
net estop-out     =>  iocontrol.0.emc-enable-in

#  ---manual tool change signals---

loadusr -W hal_manualtoolchange
net tool-change-request     iocontrol.0.tool-change       =>  hal_manualtoolchange.change
net tool-change-confirmed   iocontrol.0.tool-changed      <=  hal_manualtoolchange.changed
net tool-number             iocontrol.0.tool-prep-number  =>  hal_manualtoolchange.number
net tool-prepare-loopback   iocontrol.0.tool-prepare      =>  iocontrol.0.tool-prepared
 

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10 Apr 2023 16:53 - 10 Apr 2023 17:37 #268761 by PCW
If you get a following error when not in motion, that suggests a data integrity error
This may be because of a too long cable between the RPI and the 7C81.
1.5" max cable length is suggested, or a cable without all pins used (all RPI GND
and power pins are  used for AC ground to prevent ground bumping.)
Last edit: 10 Apr 2023 17:37 by PCW.
The following user(s) said Thank You: TallGuy

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10 Apr 2023 17:44 #268765 by TallGuy
Ah that is interesting. It is a full cable but it's 20cm (almost 8") from eusurplus.

I'll fix that - thank you and fingers crossed!

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