On Saturday 09 March 2019 14:12:43 Chris Albertson wrote: > Gene, > > Yes, the Pi has slow I/O but this thread is about the "Blue Pill" > board that costs $2.60 with free shipping. > > SO what I do is build a hybrid. The cheap little STM32F103 has many > I/O pins that are robust and even 5 volt tolerent. I use the STM32 > to connet to the world and then SPI to telk betwween the Pi and the > STM32 > > > Allof the I/O on the Pi is not slow. The current version o the pi, > to Pi3B+ can do networking at 300 megabits persecond. This is > faster then any 100BaseT device but not the 1000BaseT we would like. > None the less fast enough > > But the Pi's SPI and I2C pins on the GPIO head go DIRECT to the CPU > chip, In fact all the lines in the 40 pin header to straight to the > chip. > > Back to the hybrid system. This is thebest model and is very much > like the old PC drinving a Measa FPGA card. A the can replace the > old PC and an STM32 ( can replace the Mesa. > > Somepeople are using BeagalBone Black boards because the BBB has those > PRUs. This is like the Pi/STM32 hybrid, logically identical. > > Dn't complain about the Pi3B+. If you are still using a 100BaseT > network switch, that switch will be the bottleneck,not the Pi. > > > My hybrid right not is runing real-time control at microsecond > resolution over WiFi, I have the "blue pill" device phyically near the > motors then a short cable to a Pi3 then WiFi to my Macbook. Motors are > DC with 64 pulse encoders running up to about 10,000 RPM into a 100:1 > reduction gearbox. So we see roughtly about 10,000 encoder edges per > second times two motors in the worst case of "full speed". The PID > loops work fine even using low-end STM32 chips > Thats doing pretty good, but you're in the realm of on-offs no one else can fix too. I find thats the major objection to the pi, no one knows how it works but me.
> On Sat, Mar 9, 2019 at 5:33 AM Gene Heskett <ghesk...@shentel.net> wrote: > > On Saturday 09 March 2019 07:53:05 Nicklas Karlsson wrote: > > > > On Sat, 9 Mar 2019 at 11:59, Nicklas Karlsson > > > > > > > > <nicklas.karlsso...@gmail.com> wrote: > > > > > I think CPU Cortex-M4 is a lot slower than arduino > > > > > > > > Really? That isn't my experience. Given that the M4 is running > > > > at 120MHz and the Arduino is 8MHz and both are running the same > > > > code? > > > > > > No I got it wrong and mixed it with raspberry, I think. > > > > The pi's huge, glaring slow i/o problem is that internal usb-2 hub. > > AIUI, only the wifi and gpio bypass that huge bottleneck. > > > > > _______________________________________________ > > > 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> > > > > > > > > _______________________________________________ > > 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> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
