On Saturday 14 March 2020 12:24:25 Andrew wrote: > Hello! > > I need to control a small machine with 3 Copley Controls Junus drives > and 5V incremental encoders on the motors. > I would like to keep the cost as low as possible. Luckily Junus has > PWM inputs and I don't need analog outputs. > I am going to buy RPi 4 for this project. > 1. Anyone has experience with RPi 4 and 7i90HD via SPI link? When I > tried it with RPi 3, the link was really unstable.
I've been controling and old sheldon lathe with first an rpi3b, and now an rpi4b, and would have to say that while the 3 worked, the 4 does it a lot easier, only needing a clock boost to 800 MHz to do a really easy job of it. All thru a cascade of an spi interfaced 7i90 with 3 7i42TA's for both noise protection of the 3.3 volt fpgs, and to interface to the 5 volt world. But 3 weeks ago I found that the glue I was using to hold a trio of ATS667's I had glued to a bracket to make a spindle encoder out of the bull gear on the spindle into and encoder was being wetted by the 0w-20 synthetic oil I was useing for spindle lube, had destroyed the goop. the ATS667's came adrift and got smunched by the gear. destroying the encoders index pulse. So I have been busy rebuilding that but with JBWeld, which cancels any possibility of pushing the around to optimize the quadrature. Then some how, I seem to have managed to destroy the 7i90 at the bottom of my pile of interfacing. I am out in the wilds of WV so the earliest I can put more of those in my mailbox is at least Tuesday late in the afternoon. I also have a web site with a preempt-rt kernel for a raspbian armhf install of buster that has quite decent latentcy, and unfortunatly a linuxcnc for this install the because in machine is dowm until I get a working encoder hacked up again, has not been available for testing. All I can say is that it passed 100% of the runtests before I made debs out of. Those are all available from my site. Its not public, but click on the link in my sig, add lathe-stf to the address bar, then click on the directory linuxcnc4rpi4 to get to it. Its also about a 300kb uplink as I'm not one of the big boys. Its all I can afford on SS. The debs were made from the clone, pull to update to master but otherwise the recipe from our wiki's Building LinuxCNC, an 8 page tome, and were actually built on the rpi4b running my lathe. There is quite a list of dependencies you'll do exits over until they are installed, so the first build will sputter and stop. install as required and restart. Extra hardware attached to this pi: A 120G SSD on a usb3-sata adapter partioned for a 10G swap, and the swap file on the U-SD is disabled to take that write wear off the U-SD. Another 240G SSD on another usb3-sata adapter, partition and mounted as /media/pi/workspace which is the workspace to build all this, again to take the write wear off the boot U-SD. The kernel was built as the user pi, as were all the debs. For more earlier history, and the install instructions for the preempt-rt kernel, see the README in that directory. Be my guest. More info if your search-foo is any good can be had from the LinuxCNC forum. Be my guest. But since I put it up about 3 months back, and I have a very limited upload bandwitdh, I'm now at 59 iptables rules tp stop the damned bots whole ignore my rules.tst and insist on mirroring the whole site, which is about 30 GB. I wouldn't mine their indexing, but the want it all and all that does is an excellent job of DDOSing me, so the iptables rules are up to about 70 input lines, DROPing whole /24's. > 2. Assuming the first reply negative and I use 7i92: do I have to buy > 7i85 or 7i75 is enough protection for FPGA chip? Or is it possible to > connect encoder outputs and PWM inputs (74HC14) directly to 7i92? > 3. Any other option? Using the 7i90HD, or any of the multiple 50 pin socket boards like it, add 3 7i42TA's, just their terminal strips are worth the sheckels come time to hook it all up. They will also gobble up noise that will blow the outputs of the fpga's on the 7i90 with any ringing or noise that goes more than .1 volts below ground. You'll need enough 50 wire ribbon cable and 6 of those IDC connectors to hook up the 7i42TA's to the 7i90HD. And last, and MOST important, build with a Single Ground Bolt and Connect ALL grounds for everying ONLY to that bolt, incluing the powerline static incoming ground. Shielded cable? Ground the shield only at that bolt. Its the only way to control ground loops, ground loops that will cost you 7i90HD's. I am using the shield as ground for those ATS667's and may yet have to switch to a 5 wire+shieled cable just to get a good ground at the ATS667's, Right now its 4 wires and the grounded shield. But thats what I had at the time. > Thanks and best regards, > Andrew Back at you Andrew, and good luck. > > _______________________________________________ > 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
