LinuxCNC raspberry pi - Microcontroller to do realtime stuff

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13 May 2020 15:29 #167654 by nickom44
Hello All,

Total newbie here with regards to Linuxcnc so the question might be naive or covered elsewhere.

From what I can gather the favoured equipment to do the realtime hard grunt stuff seems to be based around some form of Mesa card. Is there information on why an FPGA is considered best option to go for.

Best regards
nick

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13 May 2020 15:54 #167657 by tommylight
Simple reason is the Mesa boards are made to do one thing, and they do that very good, while RPI is made to do a lot of things and does non of them good ! But it is small ! :)

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14 May 2020 08:48 #167713 by nickom44
Thanks Tommylight,

Does the Mesa card output pulses , bitstreams, etc that can't be handled by a low-cost microcontroller.

I'm interested in running LinuxCNC on a raspi and see the favoured option is to use a mesa card connected via ethernet (i think), the limitation with this is raspi v3 and lower doesn't have an ethernet port that can provide realtime output.

Could another option be to connect a microcontroller via I2C or SPI to the PI.

Thanks
Nick

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14 May 2020 10:42 #167719 by nickom44
Having looked at the Mesa 7C81 manual , it connects via SPI to a PI so all looks very good.

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14 May 2020 11:01 #167721 by tommylight

nickom44 wrote: Thanks Tommylight,

Does the Mesa card output pulses , bitstreams, etc that can't be handled by a low-cost microcontroller.

I'm interested in running LinuxCNC on a raspi and see the favoured option is to use a mesa card connected via ethernet (i think), the limitation with this is raspi v3 and lower doesn't have an ethernet port that can provide realtime output.

Could another option be to connect a microcontroller via I2C or SPI to the PI.

Thanks
Nick

Mesa and PiDiCnc have boards that connect to RPI3 through SPI:
Mesa 7c80 <<< do check if this is correct
PididCnc 3805 for steppers

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14 May 2020 15:29 #167754 by PCW
Also if you a are not married to the RPI idea, you could use a OrangePI
that has a built in independent microcontroller that can handle real-time tasks:

forum.linuxcnc.org/18-computer/39037-linuxcnc-orange-pi#167290

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19 May 2020 05:31 - 19 May 2020 05:33 #168228 by ttt

nickom44 wrote: Hello All,

Total newbie here with regards to Linuxcnc so the question might be naive or covered elsewhere.

From what I can gather the favoured equipment to do the realtime hard grunt stuff seems to be based around some form of Mesa card. Is there information on why an FPGA is considered best option to go for.

Best regards
nick


People choose the Mesa option because it is known to work with minimal hassle and issues. When I say minimal I don't mean easy... That prize still goes to commercial solutions.

Could it be done with a RPI alone? In theory sure. There is no existing working software or hardware setup for that AFAIK. That means you have to write all the drivers and support software yourself. When you get to this point, let us know and I can retire my Mesa cards ;-)

When I had a little bit more time I played around with BeagleBone CNC hats and various microcontrollers to drive my lathe and mill. The reoccurring problem with this stuff is that the supplied software is horrendous and integrates with nothing. Some of the best open source solutions remain the GRBL and Marlin firmware, but that's geared towards 3D printers, laser cutters and small routers.
Last edit: 19 May 2020 05:33 by ttt.

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19 May 2020 19:38 #168292 by kjames
I have LinuxCNC running on a Raspberry Pi 4, with a 4-axis TB6600 board I got from eBay. I'm not sure how well it would run on a 'proper' mill/lathe/plasma, but I have a little Sieg-X3 rebrand from Axminster that I started to convert to CNC about 12 years ago so it's not that much of an issue. I gave up about 11 years ago and spent a month or so on it a few times before giving up again, but this time I seem to be getting much further.

I can get about 2400mm/s on X and 500 on Y and Z. I don't where the limitation is but I'm working through that now..
The following user(s) said Thank You: thefabricator03

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