Raspberry PI4, MESA 7I96S problems

I started out with the RPI4 and the Mesa 7i96 (not the S version). It seemed like it worked well at first. However, I would get very random disconnects, which obviously is not a good situation, especially running large jobs. I made the decision to abandon the RPI4, and got a refurb HP mini PC and it has worked great since then. (Amazon has them for $100)

I didn't figure out why the disconnects were occurring till recently. I was working on one of my other PIs and happened to run 'lsusb' that I noticed the ethernet port was listed as a USB device, which is not a good situation for real time operation. Random disconnects explained!

Your best bet with using a RPI is using one of the Mesa boards that interface directly the GPIO

vidgabor@gmail.com wrote:

No. It's an 3 axis mini milling machine, with three steppers. I use step-dir interfaces.
 

Hi vidgabor@gmail.com,

Have you managed to get it to work, please? I am asking because I am thinking of trying out the same set up. I have a Raspberry Pi 4B with 8 GB and real-time kernel. I have not bought a MESA 7I96S yet. But I am planning too.

Thank you and best regards,

...behai.

Basically the issue is that the RPI4 Ethernet interface is connected via USB
and USB is not suited for real time.

For a RPI4 I would use a SPI interfaced device, The RPI5 (or most PCs) are fine with Ethernet
LinuxCNC motion controllers because their Ethernet hardware are not USB devices.

I was always under the impression that up to version 3 the ethernet was on the USB bus and 4 and after were on the PCIe bus.

Cant do this anymore bye all wrote:

I was always under the impression that up to version 3 the ethernet was on the USB bus and 4 and after were on the PCIe bus.

Me too !

Yes I had forgotten, its the RPI3 that uses USB --> Ethernet
I should know since I have run a Mesa Ethernet card from a RPI4.

 (I think some RPI4 --> Ethernet motion card users needed to increase
the servo thread period to 2 ms to get it to run reliably)