The Current Bread & Butter Setup?

Billy Boy wrote:

Is the rPi GPIO interface considered fully baked, or is the Mesa 7i96S the smart bet? I would totally love to avoid the $150+ for the Mesa, but only if that does not then cost me an additional $300 in labor time.

 

It depends on what you need. I don't think that the GPIO interface on the Pi is quite as good as a parallel port, and the parallel port is only supported out of habit and as a way to get new users started cheaply. 

You will get more speed out of steppers with a Mesa card, and this is not solely down to step rate. It comes down to the resolution of the increments in step rate as the system accelerates.  If the Pi can do 20kHz flat-out then the slower rates are quantised at 10Khz, 6,66kHz, 5kHz... The motor can't physically follow such large speed steps. The Mesa card can do 20kHz, but also 19.99999 kHz too. And 20.00001

But, you could start with the GPIO and see if it's acceptable for the application. 
 

Somewhat of a novice here but like you it has been several years since my last retrofit/build of a LinuxCNC machine. The last machine built was back in 2020 and the pi platform was not really a good option then. Currently I just retrofitted a full size industrial CNC router and I am using the pi5 8GB with a Mesa 7i96s. So far it has been flawless and totally stable. My motivation for using the pi is basically downloading the image and go, other than a couple of minor tweaks to the OS (my preferences) it just runs out of the box. Using the pi I don't have to worry about finding another PC that would work in the event of a hardware failure and the fact that I can make multiple super cheap fully operating copies of the OS on a SD card cannot be beat. The machine that I just retrofitted is going to be used in a production environment and will need to be totally reliable day in and day out.

One advantage of the Pi is that it is perfectly reasonable to have an identical spare to swap in in case of trouble.