On Thursday 09 August 2018 23:31:07 Greg Bentzinger via Emc-users wrote: > Greg - To Gene - and list > > > If the RPi can use SPI over a 250mm length cable at rated speed then > it is a great option. > Doubtfull
> No? How about a 150mm cable? Maybe. > > If the signal can't get off the host PCB and to the target PCB > reliably then the whole issue is a non starter moot point. As I explained in the previous post, the pi is mounted upside down, with a teeny fan under it. This puts the pi's interface connector to the mesa 7i90 on the same side as the 7i90 might be mounted, removes the need for a pin order correcting 180 degree twist in the cable, allowing a very short cable with a total signal path length of not more than 2"/50mm, and includes the 40 to 26 adaptor/spi terminator that Jon Elson drew up and is available from OSHPark at around a 10 dollar bill from 3 of them, bare, needs 3 "chip" resistors of 120 ohms. I have made a 150mm cable work, but its more error prone than the shorter version, which seems to be bulletproof. > Maybe if there was an off the shelf adapter PCB to rig a hat sandwich. > For 90% of users PCB level mods are beyond what they signed on for. What mods are you talking about? Granted, the ultra short cable I'm useing requires familiarity with a soldering iron, but I've had an iron in one hand and a scope probe in the other for a good 65 years now. I can make more of those, but I'll grant its tedious work. > SPI is faster than needed which is nice to have extra available free > time in the loop. According to a "halcmd show threads" and given the move to a slow thread for all the human interface stuffs, my pi is almost collecting unemployment. > But MACH 3, other than smooth stepper users was almost all para port. > LCNC proved it could drive parallel ports just fine. Higher level > controls Like Pico Systems and Mesa ECP/EPP based FPGA cards have > proven that an ECP/EPP connection is plenty effective speed wise. Never tried a smoothstepper, its well above my pay grade, designed to solve a windows problem linux doesn't have. I do not have a windows machine on the premises. That also explains why I've never tried MACH, any version. > > For my mill retrofit I went with a small pile of Mesa cards starting > with a 5i25/7i77 with several additional SSerial cards added to the > mix (mega overkill, and probably not really needed) ;-) > I still have a 7i43 I bought way back, and I have a lathe conversion > that has been on a back burner for a few years. I was thinking of > driving the 7i43 with a new/old stock DM510 I have had on the shelf > NIB long enough that any warranty has long expired. Sadly the DM510 is > actually less powerful than the RPi, only thing in the DM510 favor is > I can stuff it with 4gb ram. > > I have renewed my interest in the Pi because I'm looking at some > simple applications which using the Pi as the front end driving an > Arduino with GRBL is plenty. One application is a powered feed with > auto reset for my horizontal bandsaw, a second axis could be used to > auto feed the stock for the next cut using a vise clamped/unclamped > sensor switch to inhibit/resume. Another RPi + Arduino GRBL is a stand > alone programmable 4th axis indexer for manual milling - plus having > connectors that would allow bypassing the Pi/GRBL and driving the > stepper (with encoder feedback) from LCNC. > > Another project that is just on the wish list at this point is a 5 > axis tool grinder, but it might become 8-9 axis if I include > programmable form wheel dressing. (bring Whiskey and Asprin) Probably not in that order. > Currently all conversions are on hold as I am trying to make space to > shoehorn in the machinery I purchased from my Uncles Estate. I have a > Okuma LK 350mm lathe, Bridgeport, another horizontal bandsaw and a > Harig 6x18 Surface grinder. Been so much rain the soil is too soft for > the forklifts to unload. So delivery keeps getting pushed back. > Thankfully I'm not backlogged currently because after the machines are > in, then I have to go back to the old site and remove the wiring and > phase converter and install the outlets at my shop. > > Greg > > ---------------------------------------------------------------------- >-------- Check out the vibrant tech community on one of the world's > most engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
