On Monday 17 February 2020 12:01:40 John Dammeyer wrote: > > From: Les Newell [mailto:[email protected]] > > > > > Since very slow PCs with limited memory could do this as well as > > > the slower > > > > PRU processors on the BBB, I'd venture a guess that if a Pi4 can't > > do at least 50kHz stepping while also doing trajectory planning and > > screen updates there is something really 'off' with LinuxCNC. > > [SNIP] > > > > Maybe too many hardware abstraction layers? > > > > Remember LinuxCNC is designed to be a versatile, highly customizable > > and modular machine controller. It's original name Enhanced Machine > > Control reflects this. You can use it to run anything from a simple > > X,Y desktop engraver to a huge 5 axis monster with a complex tool > > changer or a robot arm. It was never intended to be optimized, > > tweaked and streamlined to wring out every last drop of performance > > for one task. You can have performance or you can have versatility. > > You can't have both. > > Thank you Les. That was a very comprehensive reply and I appreciate > the time you took to write it. > > I want the performance, not the versatility. And it appears that this > performance is only possible by offloading from LinuxCNC to MESA or > PICO or whatever. Which is why I bought the MESA 7i92H instead of > just complaining about the speed of the parallel port. > > Since I know very little about rebuilding Linux systems in general > it's unlikely at this point that I could spend any time doing even > what Gene has done rebuilding the system to run on a Pi. What he says > is a totally foreign language to me. > My apologies John, perhaps somewhat explained by the fact that my "training" is 100% from experience gained at what is sometimes called the University of Hard Knocks, which if anybody cares, is actually existed as a fund raiser for the student loan fund at Alderson Broddus University in Phillipi WV. They hold an annual dinner for graduates from UHK that costs $125, A $100 donation to the fund and $25 for the catered dinner. Other that that, my formal education stops at the end of the 8th grade, at which point I went to work fixing what was then these new-fangled things called televisions. It seems I had the "Nack", google that, but I was an electronics nerd before the word was invented. I was blessed with a mother that was the only girl in the 1929 class on aviation technology at Des Moines Technical High School, and if she didn't know the answer to a 6 yo's questions, she did know where the Madison County library was, so by the time I was 7 and about finished with McGuffies Readers in a little one room school, I was also reading high school physics text books. Making LinuxCNC run on a pi is not my first electronics project by about 75 years. Now that is slowly fading with the years, 85 now, and medical accidents that have slowed my thinker some, first of which was a pulmonary embolism when I was 79. Thats a blood clot stuck in the lung preventing blood flow to the brain and is typically slightly over 98% fatal. And that should explain why I at times ask what should be common sense questions. At the same time, I've got a lot of BTDT's I can still remember quite well. And I have a reputation for interrupting people saying it can't be done, by doing it while they are argueing against me.
Perhaps my biggest mistake is in asssuming everyone on this list is not only a machinist, but also has a C.E.T. And thats not the case for many here. The bottom line is that each of us can teach the other a lot, if a common starting point can be found, something I readily admit I am not very good at finding. > But I am perplexed that if LinuxCNC is so modular why MachineKit for > the Beagle was forked rather than maintained as part of LinuxCNC. > Perhaps the word modular is overused in this case? After all the goal > of running a RPi4 must be to have a really low cost small processor > but it does require a MESA if you want stepping pulses over 10kHz. If > the BBB doesn’t need a MESA card then the overall cost does end up > being lower. And it gets away with that by using the PRUs then that's > a good thing. But it seems that the BBB and LinuxCNC into > MachineKit were more like an exercise to see if it could be done > rather than a desire to make a smaller more modular LinuxCNC engine. > > All I remember is there was a discussion and some lamenting that the > fork for MachineKit wasn't maintained. Or that it couldn't be > maintained. > > I think partly I don't understand the difference between the current > LinuxCNC and the MachineKit LinuxCNC. What does make them so > different that a newer version of LinuxCNC with bugs removed can't be > used? Since the Beagle has an Ethernet port could I use it to run the > MESA? Or does that once again require long strings of LinuxOS upgrade > knowledge since the for LinuxCNC need a precompiled (for BBB) hostmot2 > driver? > > loadrt hostmot2 > loadrt hm2_eth board_ip="192.168.1.121" config=" num_encoders=0 > num_pwmgens=0 num_stepgens=5" setp hm2_7i92.0.watchdog.timeout_ns > 5000000 > etc... > > Again, thanks for your very thoughtful reply. > John Dammeyer > > > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
