LinuxCNC on Raspberry Pi 4

Hy Gents.

Sorry for my late reply... Thank you for your help, Iam on the way to get a system running, but i still have a problem.

1. RPI4 4GB version booted from external SSD trough 3.0USB port. Using this OS: "2021-08-01_2021-05-07-realtimepi-buster-armhf-lite-0.6.0" from unofficialpi.
2. I installed the XFCE desktop with ( xserver-xorg xfce4 xfce4-goodies) .
3. Installing Linuxcnc Uspace from buildbot "linuxcnc-uspace_2.9.0~pre0.6129.g907754aa9_armhf.deb" 
4. Then I get this latency  

I tried it with SD card ( speed class 10) but the result is worse. Anyway i will use it with 7I76e, so achieve software step generation is not my target.
But i feel something is not working properly. Do you have any idea?
Anywhere in the forum i can see good latency results with RPI4 with realtime kernel combined with Uspace.

Thank You!

Hello, I am looking to run LinuxCNC on a pi4 with 4gb, and use software step gen with a USB to DB25 cable to a cheap BOB. It's for a very simple Taig lathe. I'll control the spindle through RS485 to the VFD through yet another USB cable. Am I asking for trouble? 

Using a USB to parallel port adapter will not work, like it does not work for I86 based linuxcnc. The usb protocol does not provide a real-time connection to the individual DB25 I/O pins. It works for printers because you write a complete 7-bit character in one go, and printers buffer the input before they process it, making it much less dependent on timing.

With the RPi, you take the signals from the 40 pin connector on the board, provide optical isolation and adapt the I/O signals to what you need to drive steppers / servos and read home and limit signals. The electronics is not complicated, but requires some design and soldering work if you make it a DIY project. You could this way wire up the parallel port of a BOB, but you need in any case 3.3 to 5V signal adaption.

Linuxcnc on the RPi4 is very experimental, I have a test setup that does not work yet. This forum publishes some information on how to configure the RPi, but I have not yet seen a complete example (ie with both the required  .ini and .hal files) published here to copy as a test.

Elco
 

So there are a few options to use a RPI for cnc
First is the use the gpio header, there is a lack of documentation around this but its doable.

Second is to use a mesa ethernet card. This has the best documentation but come at a price of around 90$
store.mesanet.com/index.php?route=produc...rt=p.price&order=ASC

Third is a relatively new project. Remora.
This uses the spi output from the pi to drive a supported 3d printer main board in Realtime via SPI.
You can read about it here.
remora-docs.readthedocs.io/en/latest/

If you re just trying things out i would try and use the GPIO and some cheap level shifters.
www.amazon.com/SongHe-Channels-Converter...07YZTW2SM/ref=sr_1_4

Thanks all, I ordered a Mesa 7i96 for use with my pi. If all else fails I suppose I can use a spare desktop that needs a video card. Still waiting for parts before a test can be done.

I am having the same result. Have you gotten it to work yet?

Its a bit of a work in progress but there is a 64 bit Raspberry Pi image builder that has decent latency here:
forum.linuxcnc.org/9-installing-linuxcnc...nuxcnc-ethercat-xfce

The image built in this process is good so far.
I got VTK built last night for QTPYVCP

 I flashed LinuxCNC 2.8.1   Raspberry Pi OS based on Debian 10 Buster  on a card and tried it on a RPi400. When I first started it there were a message that the CPU is not supported but it started anyway and everything seemed to work (exept wi-fi) until I should shutdown the RPi400. I couldn't shut it down, it always restarted. What does this mean?

Many regards,  malare

malare wrote:

 I flashed LinuxCNC 2.8.1   Raspberry Pi OS based on Debian 10 Buster on a card and tried it on a RPi400. When I first started it there were a message that the CPU is not supported but it started anyway and everything seemed to work (exept wi-fi) until I should shutdown the RPi400. I couldn't shut it down, it always restarted. What does this mean?

Many regards,  malare

If you need to use version 2.8 (64-bit) you can take the image you find here.
forum.linuxcnc.org/9-installing-linuxcnc...cnc?start=120#224608

LinuxCNC also works on raspi400 (I have one and have checked) but the version is not the most recent and therefore the hal_pi_gpio driver does not work.

If you want to use version 2.9 instead you can use the image you can download here
forum.linuxcnc.org/9-installing-linuxcnc...cnc?start=130#238020