LinuxCNC on Raspberry Pi 5

I think this is particularly concerning. The ethernet connection just seems unstable. As pointed out, there simply should not be packet loss.

I will try replacing the Pi 5 with a PC tomorrow to trying eliminating the 7i96s as part of the problem.

cnc@linuxcnc:~/Downloads/7i96s/configs/hostmot2$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.

--- 10.10.10.10 ping statistics ---
7234 packets transmitted, 7233 received, 0.0138236% packet loss, time 7240ms
rtt min/avg/max/mdev = 0.101/0.106/0.132/0.002 ms

Replaced RPi 5 with HP desktop running LinuxCNC 0.29.1, connected to 7i96s over CAT6 cable.

sudo chrt 99 ping -i .001 -q 10.10.10.10

Quick test shows 0% packet loss for 40,000 packets.

And a longer test:

2312351 sent, 2312350 received  <<<<<<<  Loss of 1 packet

rtt min/avg/max/mdev = 0.177/0.266/0.455/0.019 ms

Seems ATM the RPi5 isn't the best candidate for Linuxcnc.

Here's half a days worth of pinging a 7i96S on a Intel PC:

sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.

^C--- 10.10.10.10 ping statistics ---
72908387 packets transmitted, 72908387 received, 0% packet loss, time 72908386ms
rtt min/avg/max/mdev = 0.067/0.082/0.361/0.010 ms

 

This command FOLLOWED BY CTRL+C consistently leads to a single dropped packet in about 50% of runs. Perhaps this is happening due to the Ctrl+C causing the code to exist a loop somewhere while not awaiting the last packet to return from the 7i96s...?

sudo chrt 99 ping -O -i .001 -q 10.10.10.10

569 packets transmitted, 568 received, 0.175747% packet loss, time 568ms

1400 packets transmitted, 1399 received, 0.0714286% packet loss, time 1400ms

320 packets transmitted, 319 received, 0.3125% packet loss, time 319ms

Changing to

sudo chrt 99 ping -O -i .001 -q 10.10.10.10 -c 500

where the -c 500 causes the ping code to exit after 500 cycles consistently (100%) results in 0% packet loss (ca. 20 attempts).

Probably not important, bu I cannot duplicate that:

pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
532 packets transmitted, 532 received, 0% packet loss, time 531ms
rtt min/avg/max/mdev = 0.073/0.083/0.110/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
500 packets transmitted, 500 received, 0% packet loss, time 499ms
rtt min/avg/max/mdev = 0.071/0.083/0.116/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
1143 packets transmitted, 1143 received, 0% packet loss, time 1142ms
rtt min/avg/max/mdev = 0.072/0.083/0.111/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
908 packets transmitted, 908 received, 0% packet loss, time 906ms
rtt min/avg/max/mdev = 0.073/0.083/0.114/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
565 packets transmitted, 565 received, 0% packet loss, time 564ms
rtt min/avg/max/mdev = 0.072/0.083/0.114/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
421 packets transmitted, 421 received, 0% packet loss, time 420ms
rtt min/avg/max/mdev = 0.072/0.083/0.112/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
332 packets transmitted, 332 received, 0% packet loss, time 331ms
rtt min/avg/max/mdev = 0.073/0.084/0.116/0.007 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
381 packets transmitted, 381 received, 0% packet loss, time 380ms
rtt min/avg/max/mdev = 0.072/0.084/0.112/0.007 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
588 packets transmitted, 588 received, 0% packet loss, time 587ms
rtt min/avg/max/mdev = 0.073/0.083/0.120/0.006 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
484 packets transmitted, 484 received, 0% packet loss, time 483ms
rtt min/avg/max/mdev = 0.073/0.084/0.122/0.007 ms
pcw@pcw-HP-Compaq-Elite-8300-USDT:/proc/irq/25$ sudo chrt 99 ping -i .001 -q 10.10.10.10
PING 10.10.10.10 (10.10.10.10) 56(84) bytes of data.
^C
--- 10.10.10.10 ping statistics ---
452 packets transmitted, 452 received, 0% packet loss, time 451ms
rtt min/avg/max/mdev = 0.073/0.084/0.109/0.006 ms

 

LOL wasn't sure whether you were having me on or not... anyways, I unplugged the wireless KB/mouse dongle and replaced it with a wired KB....... the 1x dropped packet issue remains. Weirdy.

So....... this morning the Pi 5 has been quite stable in terms if ethernet comms. I might naively be thought to have caused this because I added 1x 0.1 uF and 1x 47 uF/16 V electrolytic capacitor across the blue terminal block (photo a couple of pages back) which is across the +5V / 0V rail.

I did this for a few reasons. First, because yesterday I plugged in the 7i96s while the Pi was running which may have caused the Pi to reset. Possibly the voltage at the Pi dipped due to 7i96s capacitance. I don't know if the Pi has any decent amount of power supply capacitance -- perhaps it is hidden under the heatsink (not a good place for electrolytic capacitors to live).

Second, the 5V/3A Meanwell PSU datasheet does not specify the output capacitance (or stability if you add capacitance). But in any case, the resetting of the Pi could suggest it doesn't have a lot of output capacitance.

Third, the 5V rail wiring is a bit long and all over the place, so could be picking up noise from other appliances, so this could suppress it a bit.

I also raised the Meanwell 5V rail voltage from 5.0 to 5.1V at the PSU terminals. Voltage drop in the wiring is about 100 mV according to my dodgy DMM, thus perhaps the rail was causing instability.

Well, things were quite stable, so I reversed all of the above and things are still stable !!! I can repeatedly send 50,000 packets with 1 ms spacing and get 0% loss.