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Hello everyone,
As it's my first message here, let me first introduce myself.
Feel free to skip this part

So... I'm a 40+ years old electronics engineer. I'm currently self-employed, and in long term partnership with a French CNC/3D-printer vendor. I'm using Linux since kernel 2.4.18 (~20+ years), and currently using Linux exclusively.
Most of the time, I develop custom solutions to specific problems, that includes board design, firmware development, computer software, web interfaces... I also worked on few CNC-based 3D printers. (few keywords for the curious: PIC, AVR, C, C++, python, MySQL, php)
I'm quite familiar with Beckhoff and Bosch-Rexroth, as these are the most common in my area (there's Siemens too, but Siemens being Siemens, I just can't...).

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Read this as a quite general discussion about PLC synchronization, I'm currently working on a project to eject and replace any closed-source Windows-based software for CNCs (i.e. no more TwinCAT and IndraWorks, for runtime and development), and my feelings are telling me that I can easily replace existing PLC tasks (that are synchronized) with some python script (that won't be synchronized). Note, you may also think of C as a replacement for python, it's not the point here.

I'm planning to use python as a base to write PLC programs, but as I see it, it won't be synchronized with servo-thread.
Does anyone has any arguments on the critical conditions that any PLC program running has to be synchronized with servo-thread, or the opposite ?
As far as I'm concerned, I don't see anything that has any real impact of both the servo-thread and PLC task are not synchronized (read it as: I has no side-effect for the servo-task to get an action from the PLC on next cycle), but I may miss some cases.

Ofc, I don't talk about critical procedures like homing or emergency stop. I'm talking about procedures like, let's say T3 M6, this has no obligation to be synchronized, so having a python task that run independently is fine, as long as it has the correct checks and waits, and acknowledge the procedure after everything is done.

I build a small pyvcp side panel and did some gcode coding to build a test program. Not finished yet, but I think it will be handy for testing.

Random values and one can change the limits on the go via the panel.

Sorry for the bad video and picture quality. 
Video

oooh

All pins have GPIO capability (primary function) 
Secondary functions are PWM,Stepgen etc

Does anybody have a post processor that will work with Fusion 360 for LinuxCNC's  GUI QTPlasmac
Thanks

Thanks for looking into things.
I am not sure if I understand correct.
If I type mesaflash --device 5i25 --readhmid I get this



Is I/O port and GPIO refering to the same thing. In the screenshot I/O port 8 says it has no sec. (secondary?) function.


 

linuxcnc.org/docs/stable/html/config/ini...ome_absolute_encoder

if using multiturn absolute servo encoders there isn't any homing, the encoders use batteries to maintain their position and on startup of linuxcnc those encoder positions are written to linuxcnc. this is all setup inside the config files, check the docs for using absolute encoders for the correct ini settings. they are unique and special. with this once started and the encoder positions update the dro's the machine is set in the homed state. linuxcnc does not store the previous positions on shut down as they could be useless on startup even for a non absolute encoder machine which may move slightly when powered off or could be moved while powered off giving an incorrect assumed position to actual machine position.

in the sidebar tab under the WCS tab is a button named limits override but its use is somewhat finicky from my experience. it is just commanding the same functionality available via linuxcnc so the docs will have all of the use case information for how/when to use it.