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Excellent info. I've started working on a similar procedure.There are a few more optimisations but I'll test before sharing anything.
Now PREEMPT_RT is in the mainline, there are a lot of articles emerging about  RT tuning.

I've had a bunch of issues with the TB6600 drives, both missed steps and failed parts. Although they might have been knockoffs but still.
I've used the DM556 series exclusively since then with no issues.

But I've already done that, even if it have been with GRBL and ESTL instead of LinuxCNC.

I already have both the EtherCat servos and EtherCat IO so that is the way forward in this project.

Top work.

The thing is there is a few users of the RPi, I know about 3 personally, but very rarely do they post or answer any questions. So it gets left to a few to get the job done.
Personally I like the RPi5 I just acquired a second one thanks to my son for father's Day and grabbed the same waveshare housing and Nvme adapters I'm using on the mill.
I have been wondering about including a basic 3 axis Byte2Bob config in the next experimental image. Your thoughts ?
Would you be ok with some of your attachments, with due credit, being included ?

Cheers
Rob

Some advice regarding chatgpt and AI in general for help. Currently it is not a good idea asking about Linuxcnc, many many times it gives answers that make no sense and will not work.

I wonder if it would be worth having a sticky thread that is an index to some of these great posts regarding latency and such.

Hello friend, I will try to help as much as I can.
First I would like to ask what language is best for you ? I am asking this as I can only speak English. It is my hope that there maybe someone that speaks your native language and maybe able to help.

For the image the most recent can be found here:
forum.linuxcnc.org/9-installing-linuxcnc...mages?start=0#338181

Byte2Bob help can be found here:
forum.linuxcnc.org/9-installing-linuxcnc...aughter-board#339613

I hope this is a start. I will do as much as I can to help.
All the best
Rob

Hi everyone,
I’ve been thinking about how to handle the toolchanger logic on my lathe, and it’s turning out to be more complicated than I first expected. I’d like to get your opinions on the approach I’m considering.

Problems I’m trying to solve
1. My machine has a 4-position turret plus a back-toolpost. When a tool change is commanded, LinuxCNC needs to decide whether the turret actually needs to rotate or not.
2. Some toolholders can carry multiple tools, so I need a way to define several tool offsets for the same physical holder.
3. A program might use more toolholders than I currently have installed, which means a manual tool change may be necessary.
4. But if the requested tool is just another tool inside the same holder, then no manual intervention should be required.
5. I want to achieve all of this without making CAM programming more complicated.

Nomenclature
Toolholder: The physical holder that can contain up to four tools.
Toolchanger position: One of the physical locations where a toolholder can be installed.
• Back-toolpost = position 0
• Turret stations = positions 1–4
Tool pocket: A logical element in the tool table used to identify and group a toolholder and its tools. A tool pocket maps to a toolchanger position using:
tool pocket number % 5 = toolchanger position
For example, tool pocket 7 corresponds to toolchanger position 2 (because 7 % 5 = 2).
Tool table number:
The line number (ID) in the tool table.

My idea
I’m proposing to use the tool table in an unconventional but structured way:
• Every tool table number divisible by 5 is used as a toolholder descriptor.
This tool table entry represents the holder itself and indicates which tool pocket (and therefore which toolchanger position) it belongs to.
I plan to store the tool pocket number in the diameter field.
• The four following tool table numbers describe the actual tools inside that holder.
These tool entries can be used normally in CAM and have their own offsets, as usual.
In summary:
Toolholder → tool table numbers 5, 10, 15, …
Tools inside holder → table numbers (N+1) to (N+4)

Additional requirements for the component
This approach requires the component to check a few things when a tool change is requested:
• Is the requested tool number divisible by 5?
(If yes, the request refers to a toolholder descriptor, not an actual tool.)
• Does the corresponding toolholder descriptor exist?
The component needs to confirm that the descriptor entry is present in the tool table.
• Is the diameter field of that descriptor a valid integer?
This determines which tool pocket (and therefore which toolchanger position) the holder belongs to.
These checks should be fairly easy to implement.


What this should allow my component to do
• Decide when a turret rotation is required
• Decide when a manual tool change is required
• Select and apply the correct tool offsets
• Remember which toolholder is installed in each toolchanger position (even if that position is not currently active)

Questions
Does this approach make sense?
Is there anything fundamental I may be overlooking?
Any feedback or suggestions would be appreciated!

you can use this bob directly on the RPI GPIO's:

www.amazon.de/DollaTek-5-Achsen-CNC-Brea...reiber/dp/B07PNDXZQK

only need to build an adapter cable, there are no 5v comming out of the bob on the db25 side, no risk to damage the gpio's.

Bonjour,
Si je crée un script via l'utilitaire "Hole enlarge" afin de faire le surfacage d'un disque (pas d'incrément en profondeur), je lis une boucle du genre:
(Create spiral with 7 loops)
N55 o100 repeat [630]
N60 g91 g1 @  0.2889 ^-4
N65 o100 endrepeat

Dites moi SVP où trouver la documentation sur les signes non GCode @ et ^ ?

To reduce network latency:

1. Make sure basic host latency setup is done (disable power management etc)
Actions:

sudo apt update
sudo apt install net-tools

Edit your GRUB config:
sudo nano /etc/default/grub

Find the line starting with:
GRUB_CMDLINE_LINUX_DEFAULT=

Append these parameters:
quiet splash isolcpus=nohz,domain,managed_irq,1 intel_idle.max_cstate=0 processor.max_cstate=1 idle=poll

Adjust isolcpus numbers later once you know your CPU layout.
Then update and reboot:
sudo update-grub
sudo reboot

Also:
Disable CPU frequency scaling:

 sudo apt install cpufrequtils
echo 'GOVERNOR="performance"' | sudo tee /etc/default/cpufrequtils
sudo systemctl enable --now cpufrequtils

Disable power-saving for NIC and USB:

 sudo ethtool -s eth0 wol d
sudo systemctl mask sleep.target suspend.target hibernate.target hybrid-sleep.target

2. If you have an intel MAC on the host PC, disable IRQ coalescing.
IRQ coalescing groups interrupts together to reduce CPU load — bad for real-time use.
Run:
sudo ethtool -C eth0 rx-usecs 0 rx-frames 0 tx-usecs 0 tx-frames 0

Make it persistent by adding it to:
sudo nano /etc/network/interfaces

Example:
auto eth0
iface eth0 inet static
    address 192.168.1.10
    netmask 255.255.255.0
    pre-up /sbin/ethtool -C eth0 rx-usecs 0 rx-frames 0 tx-usecs 0 tx-frames 0

3. Use isolcpus to run LinuxCNC on the last CPU
You “isolate” a CPU core so only LinuxCNC and its threads run there.
Example:
 If you have 4 cores (0–3), you isolate the last one:
isolcpus=3 nohz_full=3 rcu_nocbs=3

That goes into your GRUB line (as above). Then:
sudo update-grub
sudo reboot

To verify:
cat /sys/devices/system/cpu/isolated

4.  (in conjunction with #3) Pin the Ethernet IRQ to the last CPU
(and set irqbalance to one-shot mode so it doesn't mess with the IRQ pinning)
First, find your Ethernet IRQ number:
grep eth0 /proc/interrupts

You’ll see something like:
123:   12345   0   0   0   IR-PCI-MSI  eth0

→ IRQ number is 123
Then pin it:
echo 8 | sudo tee /proc/irq/123/smp_affinity

Here 8 is a bitmask (binary 1000) meaning CPU 3.
 (Use 1, 2, 4, 8, etc., depending on which CPU you isolated.)
irqbalance dynamically moves IRQs — you don’t want that after pinning.
Edit:
sudo nano /etc/default/irqbalance

Find this line:
ENABLED="1"

Change to:
ENABLED="1"
ONESHOT="1"

Then restart:
sudo systemctl restart irqbalance

irqbalance dynamically moves IRQs — you don’t want that after pinning.
Edit:
sudo nano /etc/default/irqbalance

Find this line:
ENABLED="1"

Change to:
ENABLED="1"
ONESHOT="1"

Then restart:
sudo systemctl restart irqbalance

5. Set irqbalance to One-Shot Mode
irqbalance dynamically moves IRQs — you don’t want that after pinning.
Edit:
sudo nano /etc/default/irqbalance

Find this line:
ENABLED="1"

Change to:
ENABLED="1"
ONESHOT="1"

Then restart:
sudo systemctl restart irqbalance


To check maximum network latency:
sudo chrt 99 ping -i .001 -q -c 60000 192.168.1.10
( Assuming 192.168.1.10 is the 7I76E IP address ) 

This will run for 1 minute and print statistics


Command Breakdown
sudo chrt 99 ping -i .001 -q -c 60000 192.168.1.10

Part
Meaning
sudo
Run with root privileges (needed for chrt and for such a short ping interval).
chrt 99
Runs the command with real-time priority 99 (highest possible SCHED_FIFO priority).
ping
Standard ICMP ping utility.
-i .001
Interval of 1 millisecond (1000 Hz) between packets — very fast.
-q
Quiet mode (only summary results).
-c 60000
Send 60,000 pings, which takes about 60 seconds at 1 kHz.
192.168.1.10
Target IP address (replace with your remote machine or device).


What It Tests
Latency/jitter of your Ethernet path between your host and the device at 192.168.1.10

Consistency under real-time scheduling (since chrt gives the ping thread real-time priority).

Impact of CPU isolation and IRQ pinning on network determinism.

then

How to Interpret the Results
When it finishes, you’ll get something like:
--- 192.168.1.10 ping statistics ---
60000 packets transmitted, 60000 received, 0% packet loss, time 60040ms
rtt min/avg/max/mdev = 0.120/0.135/0.210/0.015 ms

Value
Meaning
min
Best-case latency.
avg
Typical latency.
max
Worst-case latency (what we care about most).
mdev
Standard deviation (jitter).

Good results for a well-tuned LinuxCNC host:
max under 0.5 ms (ideally < 0.2 ms).

No packet loss.

mdev small (under 0.05 ms).

Bad results (what to look out for):
max spikes to several milliseconds → indicates power management or IRQ contention.

Packet loss → NIC or cable issues.

mdev large → jittery CPU or network driver.

Tips
Make sure your Ethernet link partner (the device at 192.168.1.10) responds quickly — e.g., another PC on the same subnet, or an EtherCAT master/slave device.

Run it while LinuxCNC is idle and again under load (with the machine moving) — compare the two.

For continuous monitoring, use:

 watch -n 1 "ping -q -c 1000 192.168.1.10"
 to sample shorter bursts every second.

then 

edit servo thread time to for example Ts=333 333 ns in the .ini file

finaly

edit setp hm2_7i76e.0.read.timeout 100000      # 100μs or less depends at measured latency

and check the time of servo thread which has to be less then for example < then Ts
 

NOT can found, no have, only can use paraller port hat and paraller port breakoutboard, if want rpi use stepper drive direct need voltage level shifter board, 3,3V to 5V 8 pin converter, rpi use 3,3V and convert output can use 5V stuff, etc, stepper motor driver, step and dir pin, and enable pin. and same can bi -directional board use input too 5V sensors,limitSW etc convert to 3,3V and use whit rpi. same output relays etc, cn use gpio pin 3,3V convert to 5V and then use trnsistor who connect to relay on/off relay. gpio not handle lot current about 2mA out and in little more, or burn input/output port. thats why need converter and optocoupler to input current resistor need too, stuff not broken rpi. and shift level converter and resistor output no burn output pin, if have lot money waste buy ower price protoneer rpi cnc shield 100€ horriple price, or cheapen option rpi paraller port hat 35€ and cheap chinese 10€ breakoutboard. i think have possiple use shift level converter to input/output gpio pins and optocoupler cheap in-out system direct to driver and all limit,home,probe,etc inputs, opto input pins and shift level converter output pins, i hope working , i need test if has order all parts, but i not understand what software need do, image were is linuxcnc and how working whit paraller port hat if use, or what need hal file doing or other, programs and code not my job ,not understand anything.

That really depends on use case, sometimes both sides must be used, sometimes only one side.
I really do not think i can do a god job of explaining that, so i'll shut up.

Thanks for correcting the comment re grounds terminated at one end only. I was concerned connecting at both may create a ground loops.
Its nice to be corrected and learn better ways.

unknown wrote:

Thanks Tommy ...

You are absolutely welcomed, always.

Well, to late, but no need for any of that fuss.
We need as much info as possible for the machine, motors, drives, controllers, whatever else, and a lot of pictures of the wiring and setup.
From you picture it seems like brushed servo motors, but i can not see if they have tachos, if they do that would make them analog servo, if not then most probably position controlled with probably step/dir signals or if older with up/down control or plain quadrature.
See, to much assumptions, so more pictures.
For analog servo, you can use this howto and with a bit of time and effort have the machine tuned pretty fast:
forum.linuxcnc.org/10-advanced-configura...ning-detailed-how-to
The link above will not work for any other type of control, only analog with Mesa boards, although it works with other controllers also.