Linuxcnc on Raspberry

I have built a pcb to interface the RPi to a Ramps1.4 pcb.
It has 3 TXS0108e chips for 3.3 <-> 5V level shifting
I am in testin with it now.

update 21may2021:
The outputs of teh TXS0108e are said to be pulled up.
Well, they dont pull up to 5Vm only to about 2.7
So I added 47K pullup sip resistors.
Now the 3.3V side floats to 3.3 and the 5V side is idle at 5V
The signals now switch rail to rail.

Also, there is a race condition on OE, It has to be asserted AFTER the reference volatges are stabile,
ao, I broke out an unused Pi pin for OE

New PCBs are at JLCPCB now,
when they arrive, and are populated and test,

tomp

Is this pcb your own design? Will you make the schematics/design files open to the public?

Does this project use linuxcnc or is it still using marlin/grbl on the ramps?

1)yes , my design. and yes its free & open source ( its just a wiring harness turned into a pcb with level shifters )
2)it's for linuxCNC , the ramps1.4 itself has no brains ( it is usually plugged into a mega but not here )
also the design will work with PYcnc ( the dma stepper ).
I am waiting the 2nd revision pcbs ( more ground fill and moved 1 connector a tad )
Then will make available
here is the beta in kicad format

You should be able to an Orange pi by rotating the assembly of the shim and ramps shield by 180 degree,
It will just plug in

tomp

hello, now running kernel 5.10. on rpi4 4G
usb wifi ok without choking memory

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.10.25-rt35-v7l+ #1 SMP PREEMPT_RT Wed Mar 24 19:51:39 PDT 2021 armv7l GNU/Linux

pi@raspberrypi:~ $ free
total used free shared buff/cache available
Mem: 3919140 132908 3538204 37312 248028 3619740
Swap: 102396 0 102396

This was using the newest ( 15apr2021) from kdoren as Andy Pugh mentioned
using kernel .debs ( not building)

goto
github.com/kdoren/linux
and on right side of page, look for 'Releases'
click that
and scroll down to
"To install from deb packages, as root:"

1st get a root pwd ( google it )
2nd follow his notes
3rd reboot

the latency is not impressive for stepper people,
80uS base immediately got an UnxpectedRealtimeDelay

tomp

if you are using hardware stepping and having latency issues, perhaps try the 64bit image elvalo posted
forum.linuxcnc.org/9-installing-linuxcnc...i-4-8gb-2gb?start=50
forum.linuxcnc.org/9-installing-linuxcnc...xcnc?start=40#204950

67-80 has been pretty much the average for me accross the 32bit images ive used (without playing with cmdline stuff), but on the 64bit images, despite being power hungry, im getting 20-50 with glxgears

re elovalvo;s 64bit image for rpi 4

my interests are for native software stepping
so thats why i run these tests this way....

It looks good so far with latency-histogram --nase 80000 --servo 1000000
I booted with isolcpus-1,2,3 idle-poll
screensaver killed
4glxgears at 60fps each
at 5123 seconds (85.4minutes)
I will let it cook overnight

I will try base thread at 50us if good tomoorw morning.

this is on a
pi4 4G with arctic cooler and 3amp wall wart, logitech usb kbd&mouse
and a 30 inch hdmi display ( i dunno rez )

30.2uS max latency on base
19.5uS max on servo

thx elovalvo again
tomp

btw most problems that i encounter with img's on pi
are from the sd cards
not dd/rp-imager/balena
not bad downloads
usually the src != dest ( bad sd's )
it is important to use a write method that verifies

rpi4 4g elovalvo's 64bit img
isolcpus=1,2,3 idle=poll
screenblanking disabled
latencyhistogram --base 80000 servo=1000000
4 glxgears
after 14hrs
30.2uSmax latency
w00t!
thx again
tomp

tjtr33 wrote:

hello, now running kernel 5.10. on rpi4 4G
usb wifi ok without choking memory

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.10.25-rt35-v7l+ #1 SMP PREEMPT_RT Wed Mar 24 19:51:39 PDT 2021 armv7l GNU/Linux

pi@raspberrypi:~ $ free
total used free shared buff/cache available
Mem: 3919140 132908 3538204 37312 248028 3619740
Swap: 102396 0 102396

This was using the newest ( 15apr2021) from kdoren as Andy Pugh mentioned
using kernel .debs ( not building)

goto
github.com/kdoren/linux
and on right side of page, look for 'Releases'
click that
and scroll down to
"To install from deb packages, as root:"

1st get a root pwd ( google it )
2nd follow his notes
3rd reboot

the latency is not impressive for stepper people,
80uS base immediately got an UnxpectedRealtimeDelay

tomp

thanks that was helpful

Is there still a 30k max step rate though sence the rpi4 does not have a dedicated i/o chip like a beegle

The Mesa 7190HD is 59USD and works over SPI has anyone given this a shot yet?