Mesa - Ethernet v's PCI/e

Hi Rod. NZ mate. Yeah Makershop is local. They only stock the pci/e stuff though.

Support wise, agree. Forum support is going to be critical with the likes of PCW clearing the fog. I started snooping at the config wizard for mesa cards, yikes! Way more options and sub tabs ro get lost in compared to the parallel port version.

I already have the controller box which is a re purposed rack server case. Its not large enough to hold a pc MB, video card, ssd as well as everything else. So i am going with seperate PC and CNC boxes. Treating those as a two building blocks linked with a cable will work ok.

You do raise a good question, can anyone tell me if the pci/e board will care about the order PC vs CNC enclosure is powered on?

Cheers,
J.

The card FPGA will not care but if you use either a 7I76 or a 7I76E, the system (FPGA card _and_ 7I76 or I/O section of 7I76E) must be powered before LinucCNC can start.

Its possible to detect if the I/O hardware has power so you could make a script that just waited for the hardware to be powered up before launching LinuxCNC, perhaps with a "Waiting for system power" message.

Thanks PCW.

Assuming I am going with a 6i25+7i76 combo, my understanding from your explanation is that the PC in of itself does not care if its powered on before or after the CNC electronics are.

What matters is that when loading a config into Linuxcnc with HAL components/drivers that expect the Mesa h/w to be present that the 6i25+7i76 are powered.

Which means I can load sim configs and run simulations of gcode files to ensure it looks ok. Then power up the cnc h/w block (which would include the 7i76), restart linuxcnc with the Mesa config and would be good to home axis, setup the work piece etc etc.

If I have this all turned around just kick me and tell me what I have mucked up.

Cheers,
J.

I thought it might be useful to find and show some examples of just how fast the movement an ethernet connected board like the 7i76e can achieve. Nothing like actually seeing stuff to understand how fast is FAST.

Utilising some great footage from RodW's build:

General large scale movements.


Cutting some parts so slow cutting movements and fast rapids on repositions.


While this is plasma and not a Mill the point is to show that the 1KHz "speed" on the ethernet connections can run steppers at a pretty fast pace.

Cheers,
J.

Takes me back! I've never really paid attention to the rapids on my machine but having rewatched the video, it is pretty quick!

I'm running 5x microstepping and 3:1 on the NEMA 23 X axis and 5:1 on the Nema 34 Y axis gantry ends so the step rate is pretty high at full speed. There are a lot of hardware and timing limitations that usually prevent the full 10 Mhz stepgen frequency being used. I think from memory my max speed is about 95 kHz.

The reason the Mesa hardware gets such high performance is that it has a hardware step generator. So Linuxcnc tells it to generate step pulses at a given frequency and it does that until LinuxCNC tells it to change. LinuxCNC can change the commanded frequency 1000 times a second so it becomes a very responsive system.

Hello.
If we suppose that computer has very low jitter for example the jitter has the orange pi5.
What is the best servo thread frequency
can achieve an ethernet and a pci-e mesa card? What are the limitations of eth and pci-e buses?
For stepper systems 1khz is enough
but what about pwm like H-bridge or analog speed servos with encoders feedback to linuxcnc that needs high speed/accelaration?
1khz in this case is enough or 4-8khz has improved performance?