Raspberry Pi 4 Tutorial - fatal error

JohnnyCNC wrote:

I ran the latency test with 6 glxgears running but no other abuse.
Servo thread (1ms): 73079
Base thread (25us): 93953

If I run just the servo thread the number goes up over 100,000.

Anything I should try to lower the latency on the Pi4?

I may get a 7i76E and give this a try. Right now I'm using a 6i25+7i76+7i83

John

I have heard that using ISOLCPUS is useful on the Pi4, try isolating 2 or 3. Of the cores.

andypugh wrote:

JohnnyCNC wrote:

I may get a 7i76E and give this a try. Right now I'm using a 6i25+7i76+7i83n

6i25 on a Pi?

No, I have that on my mill using an J1900 (I think). Just playing with the Pi 4 right now.

Did you follow the instructions on the first page to edit /boot/cmdline.txt?
gnipsel.com/linuxcnc/uspace/rpi4-rt.html

JT[/quote]

I did "go by" the instructions but apparently "follow" may be too strong of a word. I must have lost my place and skipped that. Doing this late evening when I am tired and work is nagging me via email was not a good idea.

Thanks. I'll try that tonight.

Definitely do the cmdline thing, it brought my servo thread to under 50,000 with 6 gears running.


Might as well post my results. i tried doing the install from the uspace but couldnt get the rt kernel to go. at this line "make bcm2711_defconfig" i was getting an error about over riding or something with the kernels and didnt spend enough time on it (being new to rpi, please bear with me),I am also not sure where i am looking in the menuconfig to select the preempt kernel. I opted to use the premade image andy posted here (even though I love an openbox from scratch, i will try again later), forum.linuxcnc.org/18-computer/36879-raspberry-pi-4?start=70, and resumed my install from the rpi-emc page and everything seems to be working.I bought one of those new mesa cards ,the 7c81, I am also new to mesacards. I would appreciate help when the time comes in regards to the mesacards as well if you linuxcnc gurus dont mind

I had done the step with sudo nano /boot/cmdline.txt but didn't get EVERYTHING on one line. I fixed that and now I am getting:

Running 6 glxgears
Servo thread (1ms): 27207
Base thread (25us): 32552

I did get the message "Unexpected realtime delay on task 0 with period 25000"

I have some spare SD cards I'll give it a try.

John