mesaflash - default interface

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10 Feb 2022 17:58 #234495 by nighteagle
Hello PCW,

okay i understand the 10.10.10.10 idea - but how can LinuxCNC communicate with the MESA-Card if the LinuxCNC share the Network 192.168.8.0/24?

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10 Feb 2022 18:13 #234497 by tommylight
Mesa board has to be connected directly to the PC.
No switches or hubs or routers.

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10 Feb 2022 18:26 #234505 by nighteagle
Okay - i wonder now... and how can i put the PC in the network? Do you not want to tell me i have to use some USB-Stick for transfering G-Code or make Backups?

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10 Feb 2022 18:29 #234506 by PCW
Replied by PCW on topic mesaflash - default interface
A USB <--> WIFI or USB <--> Ethernet adapter is a good solution
for network connectivity if you only have one Ethernet port.

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10 Feb 2022 18:51 #234509 by nighteagle
@PCW

So if i have a Mainboard with two Ethernet-Ports then i have the same functionality like one Port with a Switch. So for me that makes no sense!? The Ethernet Ports on Mainboards go over the same bridge - like a configurable switch - means the have the same data-load and processing for the cpu - but instead of one Gigabit i have bandwith of two Gigabit on the ethernet-bridge. But the data for the milling are so much smaller than one gigabit that i think that can not be the right solution...

All of this looks like there is problem of realtime if the ethernet port have traffic - but which traffic do you have really?

It is very confusing - first Ethernet is not a realtime interface - it is the same like USB because you can not send data in parallel only serial... in this case i don't understand the problem...!?

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10 Feb 2022 18:56 #234510 by PCW
Replied by PCW on topic mesaflash - default interface
The LinuxCNC interface needs realtime communications
so cannot be shared with other traffic.

Ethernet is capable of realtime communications.
To run LinuxCNC connected to Ethernet motion hardware,
you must use a dedicated Ethernet connection. This
is why you need to add an alternate connection for normal
network connectivity.

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10 Feb 2022 19:16 #234515 by tommylight
If you have 2 ethernet ports on the PC, you CAN use one for Mesa and the other for Internet/sharing.
You can also add a USB/PCI/PCI-E to ethernet or to WiFi.
You can do whatever as long as Mesa has it's own connection to the PC.

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10 Feb 2022 19:19 #234516 by nighteagle
Okay,
so i understand now what do you want to say - this is a nice and hope all going well now realtime ethernet - because ethernet is a stochastic access-network and can not be realtime - my education is along time ago but the Framelength is about 1500 Bytes ans own Network Storage and Copy of each Mesaage - so no way for realtime.
But if we prevent any other traffic we can say only the traffic they occur between two hosts is dedicated and so we mean a pseudo-realtime.

There is another technique for realtime in automation for using fieldbusses and another protocol over ethernet with special dedicated hardware to have access of the storage of network-controller and the are not copies of dataframes to became a very quick communication - but this don't implemented in the LinuxCNC - right? And a normal PC can not have dedicated Network-Controller for Realtime :-))

I will write something for this in the documentation after some research.

So long story short - we want to bring a one to one communication without other traffic from third parties between LinuxCNC and MESA to be sure we have not a bad delay in communications.

In this case i will Use WLAN for Backup and GCode and Ethernet Port for the MESA-Card. So if i use 10.10.10.10 of Mesa-Card then i have to use a similar IP-Range on the PC - so far so good and i will explain it in the docu. Also change all IPs on the ini and hal files... to 10.10.10.10.

Thanks for your help now...

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10 Feb 2022 19:22 #234518 by PCW
Replied by PCW on topic mesaflash - default interface
Ethernet can be realtime on a dedicated link where stochastic
access (collisions etc) are not involved.

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10 Feb 2022 19:49 #234523 by nighteagle
Have you are source for this information?
I mean it is not possible with normal Ethernet-Interfaces - it is only a pseudo-realtime - because the delay is to high and the frames to small - collision not occur if you use switches. But this is all offtopic. If you have a source i will research them...

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