Raspberry Pi 4

Gene heelo
I downloaded the kernel img...
oops it changed again on 22 feb so my original thought is not up-to-date

anyway
I think you should supply the config.txt and cmdline.txt
so other users can duplicate your setup.
Because I already got the previous incarnattion (~4days ago )
and supplied what i thought were like your config.txt cmdline.txt
( which wsa isolcpus-3, no mention of idle=poll ..
thats as close as i can guess from your posts ..)
and got > 54uS right away, 4 tests,
no time to add any other processes for extra load,
and 4 cold boot retires)
so, i think there is something missing,
something outide of geneslinuxbox.net:6309/gene/lathe-stf/li...c4pi4b/rt-kernel.tgz
May be you have a low rez monitor? mine is 1380x??? not on rpinow ;-9

I appreciate your work, i just dont get the expected results.
thx
tomp

Hello,
I also used PiCNC on an rpi3b.
What problems do you find using it for rpi4/buster?

Its a great idea but the SPI is limited to thread speed
so its like the speed issues of the parallel port.

thx
tomp

tjtr33 wrote: Gene heelo
I downloaded the kernel img...
oops it changed again on 22 feb so my original thought is not up-to-date

Its not, its all root:root internally now

anyway
I think you should supply the config.txt and cmdline.txt
so other users can duplicate your setup.
Because I already got the previous incarnattion (~4days ago )
and supplied what i thought were like your config.txt cmdline.txt
( which wsa isolcpus-3, no mention of idle=poll ..
thats as close as i can guess from your posts ..)
and got > 54uS right away, 4 tests,
no time to add any other processes for extra load,
and 4 cold boot retires)
so, i think there is something missing,
something outide of geneslinuxbox.net:6309/gene/lathe-stf/li...c4pi4b/rt-kernel.tgz
May be you have a low rez monitor? mine is 1380x??? not on rpinow ;-9

I appreciate your work, i just dont get the expected results.
thx
tomp

Done, and I also updated the sha512sum for rt-kernel.tgz And I should emphasize that this is for an rpi4b and likely will perform poorly on an rpi3b, and that I don't have a latency-test other than the one that comes with LinuxCNC My monitor is a 1920x1080

Since I am not running LCNC with a base thread, use
'latency-test period'
which will complain about the missing variable, but it will run it without a useless base thread. Here its the servo-thread that counts, but be aware in this $config, there is a 200 hertz slow thread that runs the jogging stuff.

I should pack up the linuxcnc/$config dir and post it so others might see what sort of gingerbread I have added to axis, the gui, and maybe put up a screenshot in case it won't just run on your hardware. So look for those additions later tonight. Since apache2 runs in a sandbox, I have to chown it all to me while I'm making those additions, them put it back.

Take care TomP.

the spi transmits 32 bit packets at about 40 megabits/sec and rx's the 32 bit packets at 25 megabits/second. Running a 1 kilohertz servo thread, there's time to sendand rx more than 1 packet per thread execution. That's why my 26 pin cable is under 2" long, the pi is mounted upside down with a small fan under it. No twists in a cable that is actually a transmission line that way. It reports those clocking rates as its starting up linuxcnc

As for picnc, I've not heard of it till tonight, describe it please.
The config and a screen snapshot.png are now pull-able.

Take care TomP

Hi Gene,
will try your newest asap.

re PiCNC
its a hdwr stepgen for linuxcnc using a simple (hahah) chip

here's the original 3 axis version
github.com/kinsamanka/PICnc-V2/wiki

and here's a 5 axis branch
github.com/Wireb/PICnc-5axis

I talked about using it here
wiki.linuxcnc.org/cgi-bin/wiki.pl?RPi3BPreemptRT
thx Gene

Hello again

I'll try out your latest, on a Pi4 ( and Pi3 ) later today.
Will report back

Re Picnc:
Originally developed on Linuxcnc circa 2012.
I think it is OK on Lcnc 2.7 but not 2.9.
As a bare bones on stripboard, comes in at under £10
See
github.com/kinsamanka/PICnc-V2/wiki

And a mighty long thread here
www.raspberrypi.org/forums/viewtopic.php...d17afefffe677405a0ba

Cheers
MrGreg
Edit
Beat me to TJ