Raspberry Pi 4

gtt38 wrote: Nobody told which version of the RPI4 (size of memory used) and cooling.
There is a huge difference between the RPI4 with 1Go and 4Go of RAM.
Due to thermal throttling i've seen a huge difference when i installed a fan with a heater.
I don't care about latency since i'm using an FPGA. The raspberry is not the Beaglebone, there is no PRU. So using RPI GPIO for Fast I/O is limited i think.
The cheapest way to have fast I/O on RPI could be a STM32 in SPI using the Hostmot2 RPSPI driver as start.
github.com/LinuxCNC/linuxcnc/blob/master...hostmot2/hm2_rpspi.c

I came across this thread searching for info on the PICnc. It was mentioned in the MK group and while that thread doesn't sound super interesting to me , the PICnc does. Low cost isn't a huge concern for me, I'm more interested in small things that can run LinuxCNC that I can attach a custom purpose-built daughtercard to with hostmot2-like configureabillity. I was almost there with the mksocfpga which is an awesome idea, but I'd pretty much be stuck with MK and it's outdatedness and the embedded arm cores typically being a bit too weak.

I know nothing about writing firmware and such but I'm wondering if the PICnc project can be resurrected with a decent STM32 or PIC32. Is any of that code PICnc code portable to a more stout micro and an Rpi4? Is it something that the LinuxCNC code wizards would get behind?

I was using MK on a BeagleBoneBlack with a homemade cape and 3.3v to 5v translator boards. The slow graphics on the backplot never seemed to be too much of an issue. The PRU step & direction was pretty good.....but Linuxcnc has better support and seems to have more active development.

BeagleBrainz wrote: I was using MK on a BeagleBoneBlack with a homemade cape and 3.3v to 5v translator boards. The slow graphics on the backplot never seemed to be too much of an issue. The PRU step & direction was pretty good.....but Linuxcnc has better support and seems to have more active development.

I made this for the de10-nano running mksocfpga
drive.google.com/file/d/1ih-1KqdshXeu-BH...Qf/view?usp=drivesdk

That worked great but I doubt anyone is going to move mksocfpga into linuxcnc, and MK seems like it's about a year from completely stalling out.

The stm32 dev boards are dirt cheap and an stm32 based on the cortex M4 is probably plenty fast for handling IO from a rpi over spi

Someone forget to make that link shareable ?

Yeah....lots of big ideas with MK, but not a lot of work done.

I saw a while ago that someone was working with the BBB, but bare metal, for cnc motion control. Tried look for the links, but to no avail.

Personally ATM I think the ol' X86 (_64) platform has the best long term viability. As long as the PC platform still has non-usb Ethernet running MESA Ethernet motion control is still a good long team option. Even more so for those that do commercial installations. Plus the fact I am unaware of the RPi being certified for industrial use.
Now what would be interesting is a BBB with similar specs to the RPi4 and still keeping the PRU subsystem.

@Blazini,
Check PiDiCnc, they have stepper and servo +-10V boards for RPI3, so should work on RPI4.
I still have 2 of them, they do work nicely and are quite versatile. Also stackable, with IO boards available.
The stepper version has also 4 places for small drives directly on the board so it end up as a very small full control system.
I have used the stepper one for testing, a lot, it never failed.
Unfortunately, there are still no prices on their website, been told they should be around 80Euro, so very good price. The board and connector quality is top notch. And they provide 5V for the PI, so only 1 power supply needed.

Hello
I have largely replicated the same latency results as tj-33 ( Tomp ) with similar settings & loadings.
(Pi4)
Briefly as follows; (1ms servo)
Start ~ 29us
9.5hrs ~ 51us with 4 x glxgears
Ditto + web browser ~ 168us
11.5hrs ~ 191us

Looking quite positive.
Thanks to all , especially GH for providing RT kernel & stuff.

Cheers
MrGreg