RPI4 Raspbian 64 bit & LinuxCNC

There is a protection diode that dies if you hook up the gpio wrong. It heats up by the psu connector. If you remove it you may find your pi works again. But don't play with the gpio till you replace that diode.
Not always will it save you depending on how bad you messed the gpio up but it has saved me a few times.

I was having odd performance issues while trying to improve latency in different scenarios.

Ultimately, I was able to conclude that it was a matter of the Pi thermal-throttling the CPU.I found that overclocking the CPU to 2.0GHz had a small improvement in LinuxCNC's latency test, but would eventually overheat and ruin test results.


I ended up running a number of tests with a tool called "stressberry", which monopolizes all 4 cores with prime-finding and logs the internally-reported CPU temperatures. After seeing that reported temperatures were far higher than would be expected with the actively-cooled heatsink I have attached to the Pi, I swapped out the standoffs for the heatsink with ones that were about 1mm shorter to improve contact with the CPU.

This small change had a tremendous impact on the stressberry tests: 

This is the same test, run for the same amount of time, before and after.

I've been meaning to report back these finding, because I've been trying to get the fantastic results shown previously in this thread:
forum.linuxcnc.org/9-installing-linuxcnc...cnc?start=150#253623

Aaroncnc wrote:

There is a protection diode that dies if you hook up the gpio wrong. It heats up by the psu connector. If you remove it you may find your pi works again.
 

I don't suppose you have a link to something I can reference regarding this?

I am very happy with the linucnc-2.9.0pre-bullseye_arm64rt distribution from elovalvo, which is presented on page 16 of this thread. 
After a lot of troubles with other distributions, this one made my CNC machine running.

However I do have a question: how do I install additional software? I would like to install Microsoft Remote Desktop, but I cannot find something like a software center in this distribution. Any advice is very much appreciated.

Some additional information:

I installed xrdp on the RPi.
The ifconfig terminal command outputs 3 sections; etho, lo and wlan0.
The eth0 section contains this line:

inet 192.168.0.111 netmask 255.255.255.0 broadcast 192.168.0.255

On my Windows machine I opened the Remote Desktop application, entered “192.168.0.111” in the PC name field, with username linuxcnc and password cnc.

But when I connect I only see a blue greenish empty screen.
After a couple of minutes it shows a "Connection Log" (first photo), when I click the Ok button it opens the "Login to raspberrypi" window (second photo), but entering my username/password brings me back to the empty screen for a couple of minutes, until the  "Connection Log" window appears again.

 

 

rodw wrote:

This is now superceded as its in the 2.9 documents now.
Please refer to this link instead. linuxcnc.org/docs/2.9/html/getting-start...etting-linuxcnc.html [/s]

Following this recipe I have LinuxCNC running on a Pi.
However, this install does not appear to have access to the GPIO.

On Raspbian there is a file /dev/gpiomem but that isn't created on a normal Bookworm installation.

The hal_pi_gpio module uses this to access the gpio, and won't load without it.

I have a problem with a new pi4b.
hal_pi_gpio refuses to load. It states Revision 7 is not supported.
Is there a solution for this?