Denis, while GPIO was found being slow, there was some attempts to use the DeviceTree. Since the Linux kernel 3.8, it is part of the system. Here are some links:
https://learn.adafruit.com/introduction-to-the-beaglebone-black-device-tree/overview http://chiragnagpal.com/examples.html Especially the second one, gets the performance from 3.5kHz up to 2.8MHz. What is more - it seems to be possible to do some changes during the runtime (Device Tree overlays) Well, I am no HW expert, just a former scripting guy, so sorry if I am confused :-) Cheers, Petr Dne neděle 22. listopadu 2015 20:06:31 UTC+1 Dennis Lee Bieber napsal(a): > > On Sun, 22 Nov 2015 02:09:09 -0800 (PST), Marc Wells > <[email protected] <javascript:>> declaimed the > following: > > >i am newbie ,, been looking for a board and there are lots out there ,, i > >am running a raspberry pi 2 ,, to slow ,, any way . i would like a nice > >fast little computer to run my cnc , which board it right foe me > > I suspect I'm not the one who should be answering (I don't think > I've > managed to get my BBB to flash an LED using Python yet... > Javascript/Bonescript demo, yes... Python, no). > > However, in order to answer the question, one needs to understand > what > aspects your are finding "to(o) slow". Number crunching algorithms or I/O? > If I recall, the R-Pi, as with the BBB, handles GPIO via special entries > in > the Linux file system. That is going to be slow on any board since one > basically has to open/write/close the special device files to make any > change in state on the GPIO. > > If it is the number crunching side, rather than the I/O control > side, > the R-Pi 2B is a quad-core Cortex A7 at 900MHz with 1GB RAM ( > https://www.raspberrypi.org/products/raspberry-pi-2-model-b/ ). The BBB > is > a single-core Cortex A8 at 1GHz with half the RAM ( > http://elinux.org/Beagleboard:BeagleBoneBlack ). The R-Pi 2B, if the > multiple cores are used, should be faster for number crunching. > > If my understanding of GPIO via the Linux file system is proper, > there > likely isn't much of a difference between 900MHz and 1GHz -- especially > not > if the cores on the R-Pi2B are in play so one is number crunching while > the > other is running an I/O thread; the BBB would have to alternate the > functions. > > OTOH, the BBB does have a pair of specialized PRUs designed to > have > faster, direct access to the GPIO. But they aren't programmed using the > common OS tools -- and they will end up running in parallel. > > You may really be looking at a coprocessor system -- Linux > computer > with add-on microcontroller... Say an Arduino Due programmed to handle the > actual CNC machine, with its (relatively) high-speed GPIO capability, > while > using the R-Pi2B as the number cruncher, and sending path commands (simple > "MOVE TO x, y, z" to the Due; the Due then implements the step commands to > actually reach that position. The Due (a Cortex M3 as I recall) may even > have enough power to handle simple spline computations -- "SPLINE FROM > x1,y1,z1 THROUGH x2,y2,z2 END x3,y3,z3"). > > The TIVA TM4C boards use variations of ARM Cortex M4F processors > with > lots of add-on peripherals (interrupts, the 123 board has enough timers > that one could dedicate a timer to each track of a soap-box derby coarse > and still have left-overs [6 32-bit that can be split into 12 16-bit, AND > 6 > 64-bit splitable into 12 32-bit]; the 1294 "connected" has Ethernet and > lots of memory for a controller, you likely don't need the 129E "crypto > connected" with hardware encryption modules). The TIVA controllers can be > programmed using TI-RTOS -- real time OS. (You will need CCS6 to program > RTOS, but if you want simple, there is Energia -- a TIVA specific fork of > the Arduino IDE) > > > Emphasis: TIVAs are controllers [TI considers them evaluation kits > for > the chips themselves, not as a hobbyist product like an Arduino, they'd > like you to buy hundreds of the chips for embedding in your own products]. > > And yes, I'm rambling... Too many boards, not enough time {BBB, > TIVA > TM4C123, TM4C1294, TM4C129E, Arduino Due, Uno, Mega2560, BASIC Stamps 2, > 2p, 2px, Propeller -- the BS2 is really overpriced by modern standards, > and > a handful of PIC chips} > -- > Wulfraed Dennis Lee Bieber AF6VN > [email protected] <javascript:> HTTP://wlfraed.home.netcom.com/ > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
