Re: RPi + TDE + 7i90HD

On Friday 24 May 2019 04:48:50 am Dr. Nikolaus Klepp wrote: i bought a roll of 26 wire cable and a bunch of connectors 26 on one end and db25 on the other, and then discovered /I had to peel one wire off the far edge of the cable. So it fits the parport on the pc, and the 26 pin socket on the 7i90. I'd had some cable failures since, 2 or so, mainly from inadequate smunch when assembling the cables. I have never used the terminator board for a mesaflash session, but you'll need one at the pi header. Get it from OSHPark, Jon at Pico systems can give you the oshpark part number. 3 of those is less than a tenner. You'll need 3 little grain of sand surface mount 120 ohm resistors per board, a 40 pin shrouded male connector that fits the pis header on one side of it and a 26 pin shrouded male socket on the other side. The termination is simple, src term but does allow slightly longer cables, but I mounted a fan from a video card under the pi and mounted it upside down so the heat sinks are right over the fan. Turning the pi upside down put the pi's gpio hearder on the lower edge, which allowed me to use a cable about an inch long. Now, the 7i90 is a 3 volt card, and ANY noise will blow things. So get 3 7i42TA's, a 6 pack of 50 pin scsi connectors to fit the sockets on the 7i90HD, and a hunk of old 50 wire scsi cable you can cut up to hook the 7i42TA's to the 7i90. The 7i42TA's contain the noise absorbers that protect the 7i90HD, allowing the 7i90HD to work in 5 volt circuits, and they give you rows of the green screw terminals to greatly simplify hooking all this up. I made a stack useing most of a standoff kit and stairstepped them on top of the 7i90HD, so none of my 50 wire cables are over 5" long. I've got a hal file from hell, lots of gingerbread and have made a much slower thread than 1 khz servo-thread, something in the 100 to 200 hz range is working well and I put all the hand controller stuff in that thread, else the servo-thread would be too long to make 1khz work. TDE I always figured needed more iron than a pi had to spare, so mine is still running the default raspian xfce4 for a gui. With only a gig of dram, my thinking was that the pi would get bogged down in swap. Video refresh in real time is but a dream, 5-7 frames at best using xfce4. You do eventually get used to it. You'll need to locate a 3.4-9-rtai-686-pae=3.4.0 kernel and mark it with a *hold to keep apt from replacing it. It has one major bug, so the first thing you do after bootup is find the keyboard/mouse setting uttility in the menu, and make a change so it will be saved so that key repeat is limited to 15 cps or so. It boots up at about 1500 cps and that floods the usb port nearly everything but the spi and wifi goes thru to get to the outside world. Put bluntly, that causes the pi to lose key-up events, leaving the machinery you just jogged, jogging until you hit the key quickly, sending a keyup before the repeat kicks in or it hits something. Thats broken quite a few carbide tools by running then into the workpiece when the spindle isn't turning. There are a couple later kernels, but they all have this same bug. They may work now that we know how to fix it. Until the after boot thing is done, use very quick pecks on the keys. How big is the lathe? And how will you drive the spindle? I toured the local recycle places and found a pair of 1hp 3 phases on a 50 year old air compressor that came in from the local horsepistol during a remodel, and a 50 dollar bill got the hoses unfurled to cut them off the pads. I ordered bearings and replaced them in one motor, saveing it as a spare, and put the other on the end of the cables from a 1.5 horse rated vfd, and have a 30 amp corfam brick wall filter near the vfd output and another at the vfd's input, and radiated noise has not been a problem. I used a mesa spinx1 to translate the pwm to analog controls for the vfd. I can run this motor at 10hz with this vfd for around an hour before I need to let it cool. Obviously I set a current limit in the vfd to not exceed the motors FLA, and its all Just Worked. Having spare i/o's, so I also have a pair of 40 amp SSR's rigged to turn off all motor power when motion is disabled by the F2 key. So I can leave power on the pi full time. I also have a pair of the MPJA dials mounted on a replacement apron, and thats more gingerbread x2 in the hal file, but that gives me a 5 speed jog that works just like the hand cranks used to for manual control. Down to .0002" per click. My compound was smashed by a fallover sometime in its pre-gene history, so its a solid block of cast iron carved from a free sprue from the foundry that makes wheels for whites large cars (they are here in town) now (linuxcnc _is_ the compound as it can drive both to get any angle you need to a higher accuracy than you could ever set a compound to, so neither of my lathes have a compound today.) The same fallover that broke the compound, came to a sudden stop hard enough that the weight of a mounted chuck bent the spindle just a tad so I had to regrind the MT5 in it by about 5 thou, and regrind the backplates to get the chucks running true again. And I've put screw comp in the hal to compensate for most of the bed wear, diddling X by up to 3 thou depending on Z position. So I can turn a pretty good cylinder now. I've also made clamps to prevent unscrewing a chuck with the belt yelping turnaround's that rigid tapping demands. Turning around a 40 lb chuck at 250 revs takes quite some power. :) I've got some hal to tell me how far it travels AFTER the reversal command has been given, and I shorten the tap depth in the G33.1 accordingly. I hope some of this saves you some time and headaches in running machinery with a pi. *hold, here is the contents of my /etc/apt/preferences.d/kernel.pref file: ================================ Package:linux-kernel pin: version 4.4.4-rt9-v7+ Pin-Priority: 1001 Package: linux-headers Pin: version 4.4.4-rt9-v7+ Pin-Priority: 1001 Package: raspberrypi-bootloader Pin: version 1.20170427-1 Pin-Priority: 1001 Package: raspberrypi-kernel Pin: version 1.20170427-1 Pin-Priority: 1001 ================================= Good luck Nik. 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) Genes Web page <http://geneslinuxbox.net:6309/gene>