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Ethercat random jitter fix

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12 Apr 2026 12:50 #345447 by papagno-source
Replied by papagno-source on topic Ethercat random jitter fix
Just to complete the information. The xml file contains drives that aren't actually present, so you can manage machines with different configurations. The real machine only has the x-y-z axes and an analog spindle.
So address 0 (I/O card), address 1 x-axis, address 2 y-axis, address 3 z-axis. The subsequent addresses aren't actually present, but this is done so as not to change much in the .hal file.
But I repeat, on Debian 10 the same xml files are used, the function syncToRefClock="true"

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12 Apr 2026 13:18 - 12 Apr 2026 13:58 #345448 by grandixximo
Replied by grandixximo on topic Ethercat random jitter fix
sync0Shift should not be 0

sync0Shift needs to be at least a third of your cycle

Set to 500000 not 0

Also please post files as attachments, or link to paste bin or Google drive, don't paste the entire text in the forum.

Also run ethercat master command, share the output here, preferably in a text file.

I would suggest the first device to be DC enabled, which it is, and the xml devices should match what is actually connected to the machine.

Have different versions of the xml and Hal if you have different machines with different configurations.
Last edit: 12 Apr 2026 13:58 by grandixximo.

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12 Apr 2026 14:16 #345450 by grandixximo
Replied by grandixximo on topic Ethercat random jitter fix
To rule out issues with anything outside the programs, did you try to swap SSD with the debian 10 you know is working on other hardware?

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12 Apr 2026 14:52 #345452 by andrax
Replied by andrax on topic Ethercat random jitter fix
I would suggest taking an analytical approach to this.
As I understand it, 4 registers are important:
607A target-position
60FF target-velocity
and
6064 actual-position
606C actual-velocity
I simply enter a value in 607A and 60FF, and the axis moves to that position. LinuxCNC evaluates 6064 and 606C. If the target and actual values match, LinuxCNC is satisfied.
That’s my understanding.
Now the question arises: Does the axis vibrate when stationary or while moving?
If it vibrates when stationary, which shouldn’t happen, it’s constantly receiving new positions and oscillating.
Control loop?
Do the axes oscillate while moving?
Unstable, fluctuating setpoints?

At this point, I would use Wireshark to compare the traffic between the two systems.
I think the findings will be very revealing.
 

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12 Apr 2026 15:13 #345453 by papagno-source
Replied by papagno-source on topic Ethercat random jitter fix
The problem only occurs during movement and is a noise transmitted to the mechanics, the kind you usually hear about on the LinuxCNC forum.
It seems to have solved the problem. First, I restored the original lcec_conf, Lcec_coffigen, and Lcec.so files. I changed the parameters refClockSyncCycles="-1" and syncToRefClock="false" in the XML file.
For now, I've left the sync0Shift = "0" parameter.
I'll test the machine and update you on how it works.

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12 Apr 2026 15:40 - 12 Apr 2026 15:41 #345455 by Hakan
Replied by Hakan on topic Ethercat random jitter fix
There is actually a bug in the code when you use both the "-" sign and the syncToRefClock option.
Both will switch on the pll code.
The bug is corrected, so depending on if you have that version or not.
Fix: don't use the "-" sign to switch on/off the pll code. Use only the syncToRefClock option.
Last edit: 12 Apr 2026 15:41 by Hakan.

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12 Apr 2026 15:55 #345456 by endian
Replied by endian on topic Ethercat random jitter fix

There is actually a bug in the code when you use both the "-" sign and the syncToRefClock option.
Both will switch on the pll code.
The bug is corrected, so depending on if you have that version or not.
Fix: don't use the "-" sign to switch on/off the pll code. Use only the syncToRefClock option.

 

last time when I was using the syncToRefClock instead of negative cycles there was an error of synchronization ... 
[ 2129.412707] EtherCAT 0: Master thread exited.
[ 2129.412708] EtherCAT 0: Starting EtherCAT-OP thread.
[ 2129.412731] EtherCAT WARNING 0: 1 datagram UNMATCHED!
[ 2129.576578] EtherCAT 0: Slave states on main device: OP.
[ 2296.800969] EtherCAT ERROR 0-0: AL status message 0x001A: "Synchronization error".
[ 2296.801476] EtherCAT 0-0: Acknowledged state SAFEOP.
[ 2297.416576] EtherCAT WARNING 0: 6 datagrams UNMATCHED!
[ 2350.481058] EtherCAT ERROR 0-0: AL status message 0x001A: "Synchronization error".
[ 2350.481557] EtherCAT 0-0: Acknowledged state SAFEOP.
[ 2434.605096] EtherCAT 0: Slave states on main device: SAFEOP + ERROR.
[ 2434.613479] EtherCAT ERROR 0-0: AL status message 0x001A: "Synchronization error".
[ 2434.614728] EtherCAT 0-0: Acknowledged state SAFEOP.
[ 2434.832592] EtherCAT 0: Slave states on main device: OP.
[ 2574.400506] EtherCAT 0: Master thread exited.
[ 2574.400515] EtherCAT 0: Starting EtherCAT-IDLE thread.
[ 2574.400543] EtherCAT ERROR 0-0: Failed to receive AL state datagram: 
[ 2574.400544] EtherCAT 0: Releasing master...
[ 2574.400545] Datagram initialized.
[ 2574.400549] EtherCAT 0: Released.
[ 2574.405124] EtherCAT 0: Slave states on main device: SAFEOP + ERROR.
[ 2574.412778] EtherCAT ERROR 0-0: AL status message 0x001A: "Synchronization error".
[ 2574.413072] EtherCAT 0-0: Acknowledged state SAFEOP.
[ 2574.421158] EtherCAT 0: Slave states on main device: PREOP.
[ 2574.724604] EtherCAT WARNING: Datagram 000000005d8b16eb (master-fsm) was SKIPPED 1 time.

it is just foe experimenting purposes but durin negative syncs are everything rock solid ...
<masters>
    <master idx="0" appTimePeriod="250000" refClockSyncCycles="-100">    
        <slave idx="0" type="generic" vid="0x0000006a" pid="0x03000700" name="x-s343" configPdos="true">

            <!-- driver outputs setup -->
            <!-- reset number of mapped PDOs -->
            <sdoConfig idx="1A00" subIdx="00">
            <sdoDataRaw data="00 3F 6C 65"/>
            </sdoConfig>
            <!-- status word UINT16 -->
            <sdoConfig idx="1A00" subIdx="01">
            <sdoDataRaw data="10 00 41 60"/>
            </sdoConfig>
            <!-- incremental position from motor feedback INT32 -->
            <sdoConfig idx="1A00" subIdx="02">
            <sdoDataRaw data="20 00 63 60"/>
            </sdoConfig>
            <!--
             incremental position from motor extrenal feedback INT32 
            -->
            <sdoConfig idx="1A00" subIdx="03">
            <sdoDataRaw data="20 00 50 20"/>
            </sdoConfig>
            <!-- actual velocity in incremental status INT32 -->
            <sdoConfig idx="1A00" subIdx="04">
            <sdoDataRaw data="20 00 6C 60"/>
            </sdoConfig>
            <!-- internal operation mode INT16 -->
            <sdoConfig idx="1A00" subIdx="05">
            <sdoDataRaw data="10 00 53 23"/>
            </sdoConfig>
            <!-- driver warning code INT32 -->
            <sdoConfig idx="1A00" subIdx="06">
            <sdoDataRaw data="20 00 00 20"/>
            </sdoConfig>
            <!-- actual AI status INT16 -->
            <sdoConfig idx="1A00" subIdx="07">
            <sdoDataRaw data="10 01 B2 20"/>
            </sdoConfig>
            <!-- actual AI status INT16 -->
            <sdoConfig idx="1A00" subIdx="08">
            <sdoDataRaw data="10 02 B2 20"/>
            </sdoConfig>
            <!-- driver warning code INT32 -->
            <sdoConfig idx="1A00" subIdx="09">
            <sdoDataRaw data="20 00 02 10"/>
            </sdoConfig>
            <!-- define number of mapped PDOs -->
            <sdoConfig idx="1A00" subIdx="00">
            <sdoDataRaw data="09 40 6F 77"/>
            </sdoConfig>
            <!-- driver outputs end setup -->
            <!-- driver inputs setup -->
            <!-- reset number of mapped PDOs -->
            <sdoConfig idx="1600" subIdx="00">
            <sdoDataRaw data="00 3F 6C 65"/>
            </sdoConfig>
            <!--
             0x6041 0010 == register 0x6041 + value 0x10(16bit decimal) 
            -->
            <sdoConfig idx="1600" subIdx="01">
            <sdoDataRaw data="10 00 40 60"/>
            </sdoConfig>
            <!-- 0x60C1 0020 == 0x20 == 0d32 bit INT32-->
            <sdoConfig idx="1600" subIdx="02">
            <sdoDataRaw data="20 00 C1 60"/>
            </sdoConfig>
            <!-- actual velocity in incremental status INT32 -->
            <sdoConfig idx="1600" subIdx="03">
            <sdoDataRaw data="20 00 FF 60"/>
            </sdoConfig>
            <!-- opmode request UINT16 -->
            <sdoConfig idx="1600" subIdx="04">
            <sdoDataRaw data="10 00 52 23"/>
            </sdoConfig>
            <!-- digital outputs write INT16 -->
            <sdoConfig idx="1600" subIdx="05">
            <sdoDataRaw data="10 00 02 23"/>
            </sdoConfig>
            <!-- define number of mapped PDOs -->
            <sdoConfig idx="1600" subIdx="00">
            <sdoDataRaw data="05 40 6F 77"/>
            </sdoConfig>
            <!-- driver inputs end setup -->
            <sdoConfig idx="1C12" subIdx="01">
            <sdoDataRaw data="00 16"/>
            </sdoConfig>
            <sdoConfig idx="1C12" subIdx="00">
            <sdoDataRaw data="01"/>
            </sdoConfig>
            <sdoConfig idx="1C13" subIdx="01">
            <sdoDataRaw data="00 1A"/>
            </sdoConfig>
            <sdoConfig idx="1C13" subIdx="00">
            <sdoDataRaw data="01"/>
            </sdoConfig>
            
            <!-- Set OpMode to Cyclic Synchronous Position -->
            <sdoConfig idx="6060" subIdx="00">
            <sdoDataRaw data="FA"/>
            </sdoConfig>
            <!-- Set Cycle Time -->
            <sdoConfig idx="60C2" subIdx="01">
            <sdoDataRaw data="19"/>
            </sdoConfig>
            <!-- Set Cycle exp = (-3) == 10^(-3) -->
            <sdoConfig idx="60C2" subIdx="02">
            <sdoDataRaw data="FB"/>
            </sdoConfig>
        
        <syncManager idx="0" dir="out"> </syncManager>
        <syncManager idx="1" dir="in"> </syncManager>
        <syncManager idx="2" dir="out">
            <pdo idx="1600">
                <pdoEntry idx="6040" subIdx="00" bitLen="16" halPin="target-controlword" halType="u32"/>
                <pdoEntry idx="60C1" subIdx="00" bitLen="32" halPin="target-position-inc" halType="s32"/>
                <pdoEntry idx="60FF" subIdx="00" bitLen="32" halPin="target-velocity-inc" halType="s32"/>
                <pdoEntry idx="2352" subIdx="00" bitLen="16" halPin="target-internal-opmode" halType="s32"/>
                <pdoEntry idx="2302" subIdx="00" bitLen="16" halPin="target-digital-output" halType="s32"/>
            </pdo>
        </syncManager>
        <syncManager idx="3" dir="in">
            <pdo idx="1A00">
                <pdoEntry idx="6041" subIdx="00" bitLen="16" halPin="actual-statusword" halType="u32"/>
                <pdoEntry idx="6063" subIdx="00" bitLen="32" halPin="actaul-position-inc" halType="s32"/>
                <pdoEntry idx="2050" subIdx="00" bitLen="32" halPin="actaul-position-inc-dro" halType="s32"/>
                <pdoEntry idx="606C" subIdx="00" bitLen="32" halPin="actual-velocity-inc" halType="s32"/>
                <pdoEntry idx="2353" subIdx="00" bitLen="16" halPin="actual-internal-opmode" halType="s32"/>
                <pdoEntry idx="2000" subIdx="00" bitLen="32" halPin="actual-warning-code" halType="s32"/>
                <pdoEntry idx="20B2" subIdx="01" bitLen="16" halPin="actual-analog-input-1-mV" halType="s32"/>
                <pdoEntry idx="20B2" subIdx="02" bitLen="16" halPin="actual-analog-input-2-mV" halType="s32"/>
                <pdoEntry idx="1002" subIdx="00" bitLen="32" halPin="status-register" halType="u32"/>
            </pdo>
        </syncManager>
            <dcConf assignActivate="730" sync0Cycle="*1" sync0Shift="0"/>
        </slave>
</master>
</masters>
 

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12 Apr 2026 16:14 #345457 by papagno-source
Replied by papagno-source on topic Ethercat random jitter fix
I've already run tests with:
refClockSyncCycles="1" and syncToRefClock= "true"
refClockSyncCycles="5" and syncToRefClock= "true"
refClockSyncCycles="1000" and syncToRefClock= "true"
refClockSyncCycles="-1" and syncToRefClock= "true"

With these settings, the machine makes noise when moving.
Now I've set refClockSyncCycles="-1" and syncToRefClock= "false"
and the machine is working without problems so far.

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12 Apr 2026 17:17 - 12 Apr 2026 17:24 #345459 by Hakan
Replied by Hakan on topic Ethercat random jitter fix
You have actually switched off the pll, the synchronization code.
You can double-check that with the lcec.pll-err value.
If that one counts up/down it is on. If lcec.pll-err isn't moving it's off.

There is no difference in the code with "-" and syncToRefClock.
It is just two different ways to switch on the option. The actual code is the same.
The bug happens to to be when both options are used, it will be left off in that case
if I understand what I wrote by mistake once.
Last edit: 12 Apr 2026 17:24 by Hakan.
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12 Apr 2026 18:12 #345461 by endian
Replied by endian on topic Ethercat random jitter fix

xml on debian trixie
i have test refClockSyncCycles = -1 , but problem is the same
Warning: Spoiler!

 

what help me during the grinding noise was reinstall driver to chip native or dcConf assignActivate = "300" edit to something as dcConf assignActivate = "730" ... then generic driver works well ...

I have hardware which runs at 250us and generic driver was not capable therefore I searched for other way of grinding avoiding with higher value of assign ... else with native chip driver is 0x0300 good enough 

 

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  1. Configuring LinuxCNC
  3. Advanced Configuration
  5. EtherCAT
  7. Ethercat random jitter fix
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