LinuxCNC at RPI4 with using IO Pins only ?

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16 Mar 2021 08:09 - 16 Mar 2021 08:21 #202458 by herbk
Hi,
Is it possible to use LinuxCNC at an RPI4 without a mesa card?
In other words: Can i use the IO Pins to connect the RPI4 to a BOB ( like it is possible at a PC using the parallel port ) ?

Sorry for the post at the wrong forum...
Last edit: 16 Mar 2021 08:21 by herbk.

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16 Mar 2021 15:10 #202484 by PCW
Yes you can, there is a LinuxCNC GPIO driver for the RPI

Note that RPI GPIO pins are 3.3V only so any BOB used
must output only 3.3V max to the RPI , not 5V

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18 Mar 2021 01:19 #202693 by andypugh
I can understand why you might ask the question, as the hal_pi_gpio component does not appear to be mentioned in the docs.

There is a sample config which seems to be the nearest thing to documentation for it:

github.com/LinuxCNC/linuxcnc/blob/2.8/sr...hal_pi_gpio_demo.hal

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20 Mar 2021 14:12 #202985 by herbk
Thank you.

One more question: Is there still the problem with the 8GB Rpi4 ? - I have a 8GB and want to use it if possible...

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20 Mar 2021 19:00 #203014 by andypugh

One more question: Is there still the problem with the 8GB Rpi4 ? - I have a 8GB and want to use it if possible...


I have no idea. I have reports of issues with every single Pi, and reports of success with them all too. So without buying myself an example of every possible Pi to test with I have little feel for what the true situation is.

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23 Mar 2021 09:13 - 23 Mar 2021 09:29 #203365 by elovalvo

Hi,
Is it possible to use LinuxCNC at an RPI4 without a mesa card?
In other words: Can i use the IO Pins to connect the RPI4 to a BOB ( like it is possible at a PC using the parallel port ) ?

Sorry for the post at the wrong forum...


One of my students modified a CNC3018 with the following scheme.

A CNCShield has been used to support stepper drivers and to facilitate connections.


He also used a joypad as a teach-pendant.

The related hal file is attached.

File Attachment:

File Name: giuntini.hal
File Size:3 KB


The board was a Raspberry Pi 4 with 4 Gb
Attachments:
Last edit: 23 Mar 2021 09:29 by elovalvo.
The following user(s) said Thank You: Mike_Eitel, seuchato, herbk

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28 Mar 2021 13:51 #203900 by Mike_Eitel
Thx elovalo
I was always thinking if this wouldn't be working... Eventually with tmc2209.
Have bought those part some while ago but never found time to play with it.
I think this could be a cheepo solution for some first diy small "machines".

Would be nice if there would be a solution to preset the tmc parameters via serial.
I guess this could even be done "offline" before starting lcnc.
When I hear how silent my marlin controls the steppers with the tmc's.. This solution might have its charm.
Mike

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28 Mar 2021 14:21 #203905 by andypugh
Years ago I made some PCBs to connect a Pi to a DB25 port, with level conversion:

photos.app.goo.gl/auwbTXH2wa81cAqy7

I actually found the unused PCBs whilst moving some junk earlier today.
Pretty much worthless now, they are for the original Pi Model B, with the shorter GPIO connector.

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28 Mar 2021 16:53 #203915 by PCW

Thx elovalo
I was always thinking if this wouldn't be working... Eventually with tmc2209.
Have bought those part some while ago but never found time to play with it.
I think this could be a cheepo solution for some first diy small "machines".

Would be nice if there would be a solution to preset the tmc parameters via serial.
I guess this could even be done "offline" before starting lcnc.
When I hear how silent my marlin controls the steppers with the tmc's.. This solution might have its charm.
Mike


Ideally the RPI would interface to the Trinamic chips over SPI so

1. No base thread would be needed (so the step rate is not limited by latency)
2. All chip setup could be done with hal parameters

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28 Mar 2021 18:38 #203924 by Mike_Eitel
I agree Peter, but on the other side I see the parameters as a one time shot. I see no need for recurrent cpu time in precious rt. Or maybe a comp that only runs once at startup.
Can't judge the spi part, just regarded a bit around Marlin and skr-pro bord the parameter settting hw side; read and write via one pin and I believe relatively slow serial.
m5c
Mike

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