linuxcnc-2.8.0-pi4.img - no USB on raspberry pi 4 - 8GB & 2GB

What does "sudo rpi-eeprom-update" say?

I have an idea.

After installing the realtime kernel, but before reooting:

sudo apt-get install rpi-eeprom

short story: on my RPI4 4G the loss of usb is is due to >= 4G mem.
i have a full install now by adding
total_mem=3072
to /boot/config.txt
i got the fix from
www.cnx-software.com/2019/11/04/raspberr...ork-on-ubuntu-19-10/

I did the above
BEFORE installing linuxcnc-uspace
AFTER rt kernel install

( i tried installing rpi-eeprom but it was already latest)

the bad news, chromium browser wont run
complaing no suitable sandbox

i have no browser right now
but can run latency tests

i edited cmdline.txt and added
isolcpus=1,2,3 idle=poll

then for Samco's time spike
sudo apt-get install ntp

rebooted fine with usb mouse and kbd and wifi

10 minutes of aletency-histogram --base 50000 --servo 1000000
with 4 glcgears
has
base -44 +39 servo -152 +158

there's hope for rpi software stepping, esp if dblstep is fixed ( if reset pins are available... working on it.. NAP NAM not a programmer not a monkey )
tomp

apt-get reinstall chromium will get the web browser back (but might leave the tool bar icon lunching Dillo...)

There might be more going on here than we at first thought.

The first fix was to add the USB eeprom firmware loader, as on the newer boards that it held in the OS not a ROM.
But if restricting the memory changes the behaviour, then something else is at play.

tjtr33 wrote: i tried installing rpi-eeprom but it was already latest

Could you post 'sudo rpi-eeprom-update' command output?

longer testing with software stepgens shows rpi4 not suitable. I tried longer and longer Base threads and even at 100uS base I still get Unexpected Real Time delays errors. Base 100us servo 1000us, ntpd, isolcpus-1,2,3 idle=poll and ferror = 0.07. Its not up to software stepgen IMO. It is suited to use with hardware stepgens. TomP