The Pi4 and a Mesa ethernet card seemed like a brilliant idea when I bought mine ... I now regret it. The networking nightmare it has caused is painful. There is no WiFi down in my shed, only wired ethernet, so I had to put in a WiFi to ethernet bridge, connectivity is odd, sometimes it appears on the network, sometimes it doesn't.
Any bright ideas on how to add a second ethernet port to the Pi? On Sun, 6 Mar 2022 at 02:19, gene heskett <ghesk...@shentel.net> wrote: > On Saturday, 5 March 2022 19:12:45 EST John Dammeyer wrote: > > I had to clean off my workbench for another project so the Pi4 has been > > boxed for a short while. But in mentioning LCNC to a friend who was > > buying a used PC (Intel NUC7i5BNH) that he should download the latest > > LinuxCNC Image and run the latency test to see how well it would work > > for LCNC. > > > > I then mentioned I'd had my Pi4 running it but also told him about the > > one time latency message I get every time I boot it. That I suspect > > it's due to also have the WiFi running in addition to the Ethernet to > > 7i92H. > > > > So that's the background. > > > > Now the question. > > > > If LCNC has been ported over to a Pi4 should there even be a latency > > issue? It's a fixed hardware platform so that message on start-up has > > always puzzled me but since it's just for playing around on the bench > > and not doing real machining I've never really cared. > > > I've been running an old sheldon I rebuilt with ball screws etc. I have > beem told that the hardware of the pi does not make use of the isolcpus > command in the same manner that x86 hdwe does which may explain my > latency testing results being in the 12 u-sec territory which my setup > with a 7i90 using the spi interface seems to tolerate very well until I > fire up FF while the test is running, and FF is a hog, quickly pushing > the latency out to the 200 u-sec territory. However I have run a 50 loop > repeat of the lathe_pawn.ngc program, carving air while I browsed the > news sites and I can count on one hnd the number of times my lathe > actually stuttered in half and hours fooling around. > > I used the 7i90 and the spi interface to it, in order to preserve the > pi's internet connectivity. The speed of the spi interface is amazing and > I watched it on a 4 channel, 350mhz scope for hours trying to spot a com > timing error that caused a repeat transmission going either way. It > hasn't happened. There has been zero com errors. > > That protocol uses 3 gpio lines as a serial port, sending data in 32 bit > packets to the 7i90, and getting its reply's back, sending and receiving > clocks logged as it initializes the card at lcnc startup: > hm2_rpspi: SPI0/CE0 clock rate: 41666000/25000000 Hz, VPU clock rate: > 500000000 Hz > hm2_rpspi: SPI0/CE0 write clock rate calculated: 41666666 Hz (clkdiv=12) > hm2_rpspi: SPI0/CE0 read clock rate calculated: 25000000 Hz (clkdiv=20) > Note pleaase thats sending at 41.666666 megahertz, and receiver the cards > answers at 25.000000 megahertz > > I'll submit that we do NOT have in the wintel cpu family, a com speed > capable of moving data at 10% of that speed/bandwidth product. And has, > as near as I can tell, zero effect on network performance while its doing > it. So my goal of not sacrificing my network to use a cat5 interfaced > card like the 7i92 was quite handily achieved. > > If it wasn't for the lack of an spi capable interface on the wintel > stuff, AND the combined cost of the 7i90HD + 3 7i42TA's, I would have > converted every machine here to be run by the rpi4b. > > Not having tested the 7i90HD fed by a parport, in epp mode so you get all > 8 bits per byte, I'll let Peter testify as to whether or not, the 7i90HD, > using its 26 pin interface to a pc parport, is as fast AND dependable. I > suspect its just as dependable as an epp port can be, but considerably > slower. > > FWIW, I'm using SSD's on usb-3 adapter cables for workspace and swap on > that rpi4b, lots easier on the u-sd, and on raspi's buster I can build a > realtime kernel in about 35 minutes, and I can build LCNC master from > github and install the english of it, in about 75 minutes. > > About 45 minutes to build a 5.16.2 preempt-rt kernel, but I can't build > LCNC, bullseyes python-3.9.2 is to new and breaks LCNC. python-3.7 from a > buster install works fine. > > The other thing that impresses me, is the rpi4b's phenominal uptimes. I > have a teeny ups on it and a 20kw nat gas generator in the back yard that > fires up in 6 or 7 seconds so it never sees a power failure. Uptimes have > been more than 6 months several times. The monitor draws 11 watts, the > idling pi about 8 or 9, so I only shut it down to change boot cards. > > I had LCNC running but doing nothing all the time it took me to type > this, shutdown reports latency: > task: 409277 cycles, min=0.000056, max=0.017526, avg=0.006107, 0 latency > excursions (> 10x expected cycle time of 0.006000s) > > Draw your own conclusions as to whether its fit to run machinery. Works > fine for me. > > My $0.02. > > > Ideas? > > > > Thanks > > John > > Cheers, Gene Heskett. > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > > > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
