On 10/13/2016 8:01 PM, Chris Albertson wrote: > > For sophisticated motion control you really need both. (my internet is > in robots, no as much CNC) One to run an OS and drive a user interface > and screen and talk over a network and so on. and a smaller processor > to make I/O lines go up and down and drive motors and read encoders. > In LinuxCNC we sometimes have two processors a PC and a Mesa card. > On an ARM based CNC, I think you'd see an "A" type perhaps it is a > Raspberry Pi or perhaps it is an iPhone app. Then you'd have "M" > types physically driving the hardware.
This is what I like about the BeagleBone (the PRU substitutes for a Cortex-M for hard-real-time bit-twiddling) and the Xilinx/Altera SoC+FPGA combinations (where you can put the Mesa open-source VHDL firmware in the FPGA). It works particularly well if you drive the servo-thread timing via interrupts from the hardware (with position captured by the hardware when it fires the interrupt), thus side-stepping the relatively poor ARM Cortex-A interrupt latency and jitter. -- Charles Steinkuehler char...@steinkuehler.net
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