On Sun, 28 Apr 2013 12:55:17 -0500 Jon Elson <el...@pico-systems.com> wrote:
> Is there a consensus about BeagleBone vs. Raspberry Pi? I feel the need to defend the Pi, Cubie, Olimex, et al boards, since it appears that no one else will :) Several areas of concern are worthy of our attention, which argue for a more circumspect outlook regarding the explosion of new ARM based systems that can potentially host linuxcnc: 1. In the case of the Pi, numbers matter I think. AFAIK, the Beagle Bone has two versions which have been produced; The BBW which was produced in a quantity of 60,000 (correct me if I'm wrong please), and the BBB which is being produced in a batch of 100,000 initially. Contrast this with the Pi, which has a total production of >1,000,000 (most are Model B, and I don't know how many of Model A). Also, AFAIK, none of the Allwinner A10/A20 boards has been produced in anything like these quantities AS A DEVELOPMENT BOARD. The Allwinner chips are however INCREDIBLY POPULAR in tablets and other applications. An Allwinner board like the Cubie, or even the Cubie itself, could become available in a week, month, or year, that creates as big a stir as the release of the BBB did a few days ago. Then, there's the iMX233 based stuff (far example https://www.olimex.com/Products/OLinuXino/iMX233/). This processor is very cheap, and available. It's not as super powerful as the others, but could play a useful role, perhaps as a network connected, smart peripheral controller. My point is: It's way too early in this situation to declare a "winner". In fact, the linuxcnc future may involve solutions which employ more than one of these technologies. 2. The PRU is a TI specific thing. My best guess is that BBB solutions are going to lean on the PRU for all it's worth (which is a good thing). However, the PRU is not going to scale up as far as FPGA solutions will. For a real world example, the Smithy 1240 (early 2 phase motor models), used a stepper drive with 400kHz maximum step pulse frequency and normal operation of the machine at rapid speed used the whole 400kHz. The biggest configuration of this machine had (3) 400kHz axes, and one (rotary) at 200-250kHz. Additionally, there is a 720 line spindle encoder that has to work at up to 6000RPM (the A and B channels will max out at 72kHz). This example is far below the desirable maximum limits we should impose on potential linuxcnc users. 3. Cost: Pi=$25-$35, BBB=$45. Since the difference between production cost and retail sales price is usually a factor of 2-3x, this means a BBB solution will sell for at least $20, and as much as $60 more than a Pi based one, all other things being equal. Since both boards require at least one additional circuit board for isolation and level translation purposes, the $10-$20 difference in price between the two boards would just about cover the cost of adding an FPGA to the Pi's auxiliary PCB. A Pi+FPGA > BBB+PRU assuming software support for both in linuxcnc. 4. If linuxcnc3 supports distributed processing, and network interconnection/cooperation, then these cheap little boards could be spread out in a cluster, which is much less practical with even small PCs. The small size, low cost, and low power requirements make this very attractive AND allows each different type of little board to be applied where it makes the most engineering and financial sense. This also argues for not narrowing our focus strictly to the BBB. 5. Most of this debate is moot, because the REAL FUTURE is (IMHO) going to be in these combo ARM+FPGA chips like the Xilinx Zynq and Altera Cyclone SoC devices. This type of device will likely render the existing boards we're looking at now obsolete within a few years. Any attempt to predict the future past about 5 years is probably futile. Having said all this, I did get a BBB in the mail yesterday, and I will now play with it... :) Thanks, Matt ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_apr _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
