On Monday 09 October 2017 12:57:45 Nicklas Karlsson wrote: > On Mon, 9 Oct 2017 12:36:20 -0400 > > Gene Heskett <ghesk...@shentel.net> wrote: > > On Monday 09 October 2017 11:45:58 Nicklas Karlsson wrote: > > > > > There ARM M is tiny and dirt cheap and is very good for > > > > > real-time work. I have a robot with four motors and encoders > > > > > and get 44,000 interrupts per second > > > > > and much better real time latencies then from any Linux based > > > > > solution on any platform. > > > > > > > > > > My solution for robot control is a hierarchy with ARM M for > > > > > the lowest level, then > > > > > Raspberry Pi 3 connected by high speed serial. > > > > > > Right now I am at this point with high speed serial communication > > > to ARM for the lowest level. > > > > > > > I did succeed in building a fully rt-preempt 4.9 kernel on it > > > > today, took about 4 hours, but I've not yet attempted to boot it > > > > as I saw some stuff go by during the build (when I wasn't > > > > checking my eyelids for leaks :) that I yet need to turn off. I > > > > think, other than fine tuning the kernel build, that convincing > > > > the hm2_rpspi driver that it should run on the rock's rk3328, > > > > arm64 quad core SoC, running at up to 1.5GHz should be the last > > > > major hurdle to making linuxcnc run on it, ... > > > > > > Happen to know how many SPI ports there may be? > > > > This driver that Bertho Stultans wrote, can do 5. Over 2 pin groups > > IIRC. However since I was the lab rat, only the SPI1 set has been > > extensively tested. > > There is hardware support for 5 SPI ports, or?
Software support, depends on the gpio's not being otherwise occupied. The driver of course can move those around, which would need a new cable to be made. > > > the "rates" are the write, and read, clock rates, corresponding IIRC > > to a 41 megabaud write to the 7i90 rate, and a slower 25 megabaud > > rate for reading back the data from the 7i90. > > I figured around 100kbit/s full duplex is what is needed per axis, it > should be possible to squeeze into a 1Mbit/s CAN network but it's at > the limit. UART would work but setting baud rate for speeds above > 1Mbit/s might have accuracy problem. 5-10Mbit/s SPI give me about 5-10 > times more bandwidth than needed. > > > Both of those rates could probably be improved with stronger, as in > > faster rise and fall times in the pi's pin drivers, they are a tad > > puny. > > Delay is a problem for the signal coming back. > > > The interconnect cable between the pi and the 7i90 is only about an > > inch long ... > > No need for driver here, in these cases SPI make sense, fast and > cheap. > > > > Regards Nicklas Karlsson > > ---------------------------------------------------------------------- >-------- 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 > Emc-users@lists.sourceforge.net > 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
