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cakeslob wrote:

ohhh you are using debian instead of raspi-os. that would explain why things arent working. I do not think you can change things with a config file like with rpi-os or use raspi-config, as debian is not using the dbts. I also dont think the hm2_rpspi driver works with debian bookworm anyways

Unfortunately I am not using raspi-os indeed, because as far as I know the "LinuxCNC 2.8.1 Raspberry Pi OS based on Debian 10 Buster" (which is on the LinuxCNC frontpage) is incompatible with RPi's that have been sold over the past two years...

Oh, it's top top secret. You have to be an inner circle member to buy it.

I didn't realize what you were specifically interested in. Yeah, the spacing of the holes in relationship to the header on the Raspberry Pi boards does seem like a design oversight. I mounted the stand-offs on the board and tried to plug the cable in and said "what the $@%!#^?". The Stand-offs I bought are plastic, so i put them in a vice and filed them as close to the center hole as possible. If you look closely at the attached photos you'll see that the sides facing the connector are flat. It just fits. I created the "top hat" that the fans are mounted on in SOLIDWORKS, and 3D printed it. So I needed to flat file four stand-offs. Here are the stand-offs and screws I used.
www.digikey.com/en/products/detail/essen...M025045G008/11637936
www.digikey.com/en/products/detail/w%C3%...ik/971180155/9488784
www.digikey.com/en/products/detail/w%C3%...ik/970170155/9488718

Best,

Gene
   

 

Thanks for your advice, but where in the start menu could I find the setting? 
When I Google it it looks very easy, but all the explanations seem to be aimed towards Raspberry Pi OS. In my installation I for example don't have the "Preferences" button, my start menu looks like this:

Thank you for your comments! 
Today I tried readhmid, but the response is still “No 7C81 board found”



This did however not surprise me, as I have not enabled SPI manually, I didn’t succeed in that yet:

Google tells me I should do this via raspi-config, but that command is not found, although I updated and upgraded my install. Perhaps that is because I am not using Raspberry Pi OS?
I am running Debian Bookworm instead (build date 2023-01-01, from this page: raspi.debian.net/tested-images/ )

 

Next, instead of using raspi-config, I tried to change the setting manually in the file boot/config.txt.
On the RPi this file does not exist, so I put the SD card in my Windows machine and opened the file there.
But the config.txt file told me not to modify it, but go to another file instead.



 

I tried to create a new textfile and save it as /etc/default/raspi-extra-cmdline, but this is not possible. I received the warning “The document is read-only, do you want to save it as another file?”.



So unfortunately I haven’t been able to enable SPI. Perhaps am I doing something wrong?

TFTP upload of the configuration file is "knda" working... well the TFTP server is happy but the data isn't

I will need full debug capability to understand where my memory addressing is wrong. I'm reading data out of the wrong region or something...

I did bring my ST-Link converted to CMSIS-DAP probe with me but the SDK debug does not like the firmware version as some commands are not implemented.

So, I've ordered a Raspberry Pi Debug Probe, which will be waiting when I get back into Oz. This probe may be a nice out of the box use for the RT1052 boards as well. The Pico is also so so cheap and easy to program that a normal Pico would be a simple option as well.

I would start with trying to readhmid or something first
Its been a few years since I did it, Ill have to find which rpi had my notes, but from what I remember, it was something to do with

--spi
or the spidev address,
or turning on spi manually when trying to use it

edit, I found my notes. they look pretty contrived, but I think this was the successful part, as it was the last entry in my notes. its been a few years since Ive done it, so maybe its different now

Hi HansU,
I am sorry for my late reply (I didn't have a lot of time unfortunately lately to play around with my RPi) but I tried this and it did indeed solve my issue. I am now able to build a nice and functioning GUI, something I was looking forward to for a long time.
Thank you!

Perfect! Move on to the next challenge.

Here are the latency results. Both are with two glxgears processes running.
 

 

Good enough.

I think isolcpus is the right tool for Linuxcnc.
I have been doing a bit of kernel tracing with mentoring from a couple of guys from the RT kernel team.
Linuxcnc (setup for Mesa) only uses one thread so it picks one of the isolated CPUs.
We never need to turn it on and off. I think cpuset would need implementation in the code.

Probably using cpuset when starting the threads  in the source only while Linuxcnc is in operation could improve performance if it's not in use
But moving 69 threads seems wrong!

With the dietpi image I setup I was averaging around 40us with 5 x glxgears running and no real overclocking
So it sounds about right although I think it'll vary based on the kernel version.
6.3 onwards for the newer ones, and maybe 5.4 / 5.10 for the older ones, with the ones inbetween possibly being worse.
As others have said though I don't think it should matter if you're using a mesa card.

My understanding is there's normally two threads, the base thread and the servo thread.
Without a mesa card (such as using the GPIO pins to drive stepper motors directly) the RPI has to do the base thread and generate lots of steps very quickly
With a mesa card that part of the workload is offloaded so the Pi has less to worry about and just manages the servo thread.

If you really want to push things, I think with the newer Pi4's you can run them at 1800 instead of 1500 for the frequency
but it's probably not worth it if there's a mesa card in use
www.raspberrypi.com/news/bullseye-bonus-1-8ghz-raspberry-pi-4/

I did see the same thing in so far as isolcpus being depreciated when I was digging around for options to try out.
I think it's because once it's set at boot time it can't then be changed later on.

cpuset allows you to dynamically turn stuff on and off whenever you want at runtime so is more flexible.
www.spinics.net/lists/linux-rt-users/msg25176.html
www.codeblueprint.co.uk/2019/10/08/isolc...eprecated-kinda.html
stackoverflow.com/questions/11111852/how...eduling-threads-onto

However I couldn't get it to work as far as linuxcnc.
I think cpuset shield is supposed to do the same job as isolcpus at runtime
But when I tried it the historgram wouldn't run, so maybe a linuxcnc bug as far as supporting shielded cpu sets, or maybe it's the wrong method.
 

Interesting. Yet in other places kernel.org has docs for isolcpus without mentioning that. Linuxcnc is not a complex applictation, and we are users not developers. isolcpus generally gives performance improvements as it isolates some cores that are basically exclusively available  for Linuxcnc's real time threads.

In recent testing this week we saw latency drop from about 90k to 50k by adding isolcpus=2,3 for the Pi.
If you are getting latency of 60k, move on and worry if it doesn't work. I'm sure it will be fine.

It's a bit involved, but we put a guide together here for inclusion ito the Linuxcnc docs. There are a few more tweaks there you can try...
github.com/rodw-au/linuxcnc/blob/rodw-ge...sing-debian-bookworm
But don't bother with this unless yours stops working...

​​​​
 

Awesome work!
Is there a working image available yet?
How can the GPIO be configured for LCNC?

Thanks for confirming that I'm chasing my tail and wasting time.

There is a lot of conflicting information on the internet regarding how to reduce jitter in Linux. That typically means black magic time sink that varies greatly from setup to setup.

Moving forward.

@rodw -This is from kernal.org
 

Best,

Gene

Isolcpus is not deprecated. Its purpose is to isolate some cores to only be used by real time threads.
Our testing showed improvements with isolcpus=2,3