Retrofitting a 3-axis VMC with DC servos - guidance needed

Hi everyone,

I've just purchased the host PC and I'm waiting for it to arrive so I can set up the RT-OS and start digging into the retrofit.

To practice on the bench and learn the ins and outs of LinuxCNC, I put together a Mesa hardware stack: 7i97T + 7i74 + 7i84U + 7i73.

I have a quick question regarding the initial configuration workflow. From what I’ve gathered reading through the forum and docs, the easiest path forward seems to be:

Use mesaflash to flash the proper binary (.bin) to the 7i97T so it supports the Smart Serial expansion through the 7i74.

Once the main FPGA board has that specific firmware, use mesact to configure the machine basics, pinout, and closed-loop settings.

Regarding step 1: Is mesaflash strictly necessary for this, or can I flash the firmware directly from within mesact? From what I've seen in recent updates, it looks like mesact has a built-in flashing utility that might work for this. Is that correct and reliable for ethernet cards?

Lastly, I’d love to get your advice on the best learning path to fully grasp how Mesa cards interface with LinuxCNC. Should I just wire everything up on the test bench and learn by trial and error, or is there a specific documentation, manual, or forum thread you'd recommend reading first to avoid spinning my wheels?

Thanks a lot for all the help!

Japoo_Ness wrote:

Lastly, I’d love to get your advice on the best learning path to fully grasp how Mesa cards interface with LinuxCNC. Should I just wire everything up on the test bench and learn by trial and error, or is there a specific documentation, manual, or forum thread you'd recommend reading first to avoid spinning my wheels?

Depends a lot, but documentation is a nice start, browsing this forum helps a lot, and there are tutorials/howto's for near everything be it very nice or chaotic written by me.
But nothing can replace the hands on approach: wire stuff and test while reading and checking pictures.
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This last is how i learned last few days that Pico2W is utterly useless as a flight controller, for many, many reasons, but mostly their (anything RPI) being convoluted and disorganized beyond belief for something normal people should use, requiring hundreds of libraries, and never ever consistently building firmware without complaint.
No wonder ESP32 won, much cheaper and much faster and most importantly with flash memory.
Next, use that Pico2w for LinuxCNC, oh joy!

I've just finished installing the system, disabled all power-saving features (C-states, SpeedStep, etc.) in the BIOS, and isolated a CPU core using isolcpus.

Here are my latency test results while stressing the system with 4 instances of glxgears and a YouTube video playing in the background

Note: I am currently running this test using an old VGA monitor. I suspect the analog output/Xorg driver might be causing some minor latency spikes compared to using a pure digital connection, but I'm not entirely sure.

What do you think of these numbers? Are they good enough to move forward with my Mesa setup, and what should my next steps be?

Thanks in advance for your feedback!

Looks fine but for mesa its better to run: latency-histogram --nobase --sbins 1000 --show to get rid of the base thread window which gets in the road. and can suppress results. Run that and reshare.

This are the results
for what i understand are good for mesa Ethernet boards
Now i´m gonna try to make connection to the board
its that okay?
 

Looks OK, so test with the Mesa attached and a running config.