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Month: March 2018

Re: [trinity-users] my silly project continues

From: Gene Heskett <gheskett@...>
Date: Tue, 20 Mar 2018 12:05:19 -0400
On Tuesday 20 March 2018 08:19:14 Dr. Nikolaus Klepp wrote:

> Hi Gene!
> Am Montag, 19. März 2018 schrieb Gene Heskett:
> > [...]
> > The install is armbian jessie lite. Downloadable from the armbian
> > site LinuxCNC is the uspace version of 2.8-pre. Weird config, no
> > PID's used Works fine.
> >
> > PM me, and I can send you what should be working configs IF you've
> > installed and wired up a pair of MPJA's 100 ppr a/b encoders to
> > function as hand wheels. This encoder is also available elsewhere,
> > s/b under $25 a copy. Interface is a mesa 7i90HD, with 3 7i42TA's to
> > protect the 3.3 volt 7i90HD from the noises. Spindle control is a
> > 240 volt single ph input 1.5 hp vfd, running an old (probably about
> > 40 yo) 3 ph, 1 horse I took off a scrapped air compressor.
> > But no use further cluttering this list, so PM me.
> Thank you for your hint. Sorry, no mesas in my shop, but at least I
> have some encoders waiting :-)
> Ages ago I had a single RPi2 (the newer ones) running with linuxcnc +
> TDE and GPIO for signals, just like the parallelport. Latency was not
> so great (~ 20000ns), but at least the steppers turned. Last week I
> wanted to resurrect the project, just finding the RPi beeing unable to
> boot. Well, following your hints I came to the conclusion that almost
> anything is better than a RPi for CNC (oh my, never thought I would
> write that).
> Now I've placed a T60 mainboard into a 15.4" T61p with libreboot
> (stock bios gives horrible latency) + linuxcnc + TDE + NativeCAM,
> looks neat and has nice latency (<2000ns).
> Nik

You will never generate software stepping thats usable on an r-pi w/o the 
mesa stuff. Does away with the base-thread. But as I added more ginger 
bread, to the halfile, I got to thinking that the stuff I has hacking 
into the halfile didn't even need a servo-thread speed, so I setup an 
even slower thread at 200HZ for that stuff & all works as expected.

2 main problems with the r-pi3b, only one of which is eliminated by the 
mesa interfaces, the other being that with anything like a rtai kernel, 
it throws away mouse and keyboard events. In wholesale quantities, 
depending on which hand my coffee cup was it when it was power cycle 
rebooted. If I could buy or build a usb<->spi interface, I believe that 
would also go away because I think its all data collisions in the 
internal usb that are causing the event losses.

But when its acting sicko, anywhere from one to 10 reboots will finally 
fix it and I've had month's of uptime's w/o this problem.

I've bought a couple rock64's, with 4 gigs of dram.  Dozens of times 
faster than an r-pi3b. But changing the kernel to one that can run 
LinuxCNC, takes more knowledge of how u-boot works than I have been able 
to connect with.  And the guys at armbian who could educate me, simply 
ignore my questions.  I've had both jessie and now stretch installed on 
them, and jessie is far more stable.  jessie runs great on the pi's.

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)
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