Is a raspberry PI a real host solution for LinuxCNC right now?

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08 Apr 2022 10:01 #239644 by marafado88
Hello everyone,
I've two old home grade mid-towers in two CNCs, both with old linuxCNCs running.
This is a benchmark of the best of those two: prnt.sc/Afggkk9KuaUU
And I am looking for a machine that could control those CNCs but fanless and with a small footprint, like a mini desktop or even a raspberry pi.
The raspberry pi seems a interesting alternative in terms of dont having a fan, small footprint, and the possibility to use an USB to Parallel port.
My question is if I can use a raspberry pi (If yes with what specs), or if a mini desktop with enterprise grade hardware is better.
Thank you,
 

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08 Apr 2022 12:07 #239657 by Aaroncnc
Yes a rpi 4 can be used for linux cnc.
Is it better than a desktop that im not sure.

Also usb to parallel ports dont work with linux cnc for real time control. These usb adaptations use buffering that prevents realtime control.

The pi's have a few control options.

The most feature complete and best documented is to use a mesa ethernet card.
store.mesanet.com/index.php?route=produc...r=ASC&product_id=311

The second option with less documentation and some speed limitations would be to use the GPIO on the pi itself.

Third is the remora project that uses 3d printer main boards connected to the PI via SPI for realtime control.
This project is new and documentation is improving, But i think there are only a few members maybe 4-5 have tried or using it.
remora-docs.readthedocs.io/en/latest/

I would not replace something if its not broken or limiting me.

Latency is not a big deal when using a mesa card or remora as the Realtime base thread is offloaded onto the connected real time boards.
The following user(s) said Thank You: marafado88

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08 Apr 2022 14:02 #239673 by rodw

Latency is not a big deal when using a mesa card or remora as the Realtime base thread is offloaded onto the connected real time boards.

Its not actually the base thread being offloaded. Its just doe differently. LCNC tells the mesa stepgens to run at a specific frequency forever unless I tell you to change it which lcnc can do 1000 times a second.

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08 Apr 2022 14:37 #239675 by Aaroncnc
interesting.

In my simple understanding then lcnc sets the clock and the board just run at the set time.
But the thread and instructions and Realtime nature are then off loaded onto the board itself.

Could you expand on it a bit more? Is it more that lcnc running the instructions still in a base thread of sorts then sent to the board to run on its set time but not doing the logic on the board itself?

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08 Apr 2022 15:41 #239676 by tommylight

..... which lcnc can do 1000 times a second.

It can do that 4000 times a second, i was to scared to push it further! :( Chickiiiin

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08 Apr 2022 15:55 #239678 by Aaroncnc
Also some of us put fans on our RPI4, its not needed but i like to overclock it to the max and then some.
Also its adorable. 
 
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09 Apr 2022 22:35 #239785 by andypugh
I made an Aluminium case modelled after the Mac Pro:
The following user(s) said Thank You: tommylight, fletch, tlflow

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