Gene, > Can this bbb support at least two dozen or so bi-di gpio's, 4 or 5 > stepgens, at least 1 pwm, and at least 3 abx encoders? Drive a > 1920x1280 full color monitor at a frame rate above 5/sec? At what total > cost?
The BBB has more I/O on it compared to the Pi and includes A/D. Where it really fails is that the HDMI isn't well set up for 1920x1080P HDMI. As a result the graphics side is a bit clunky. But then LinuxCNC or the original EMACs ran on a much smaller PC. MachineKit on the BBB does run with the Xylotex Cape. I think for anyone wanting CNC with a small module it's a far better starting point. And realistically how many people are really working at the low level where the processor architecture matters? If you want lots of I/Os then SPI can do this. I think there are 3 quadrature inputs on the BBB processor but it may be only two. Not sure there. I've done a pseudo real time project with the Pi but to make it work I had to use a Microchip PIC32 to capture and buffer the first 20 seconds of high speed CAN messages along with time stamping when they arrived. Then, when the Pi was finally and we'd acquired the GPS Time of Day awake I used SPI to bring the stored messages into the PI, retroactively adjust the TOD to match real time and save to files. A different task ran in the background reading the files and posting them up to a cloud database. The point is, to do what we needed, the Pi needed an external co-processor. The BBB wouldn't have been any better since the bottleneck is the Linux boot time. Only dedicated hardware is there within milliseconds of power applied ready to work. That's not needed for a CNC system but waiting a minute after you turn on power is annoying. John _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
