> From: Nicklas Karlsson [mailto:nicklas.karlsso...@gmail.com]
> On Sat, 23 Jun 2018 21:04:48 -0700 > "John Dammeyer" <jo...@autoartisans.com> wrote: > > > But we are still talking about a Multi-Tasking, Round Robin Priority Driven > > OS right? Like 3 tasks with the same priority are time sliced with equal > > processing time? ... > I think an excellent example of a "hard" although not neccessary critical real > time process is to read data from some kind of serial receive buffer. If dead > line is set to buffer full and trigger then half full I think this example will fit > perfectly with the theory. In case hardware to trigger real time process, > usually an interrupt and pirority is available theory will fit with practical > implementation. > > > Inter task communication done with pipes. A task can > > suspend on a pipe until it's written to by another one. ... I did a project like that last year with a Pi and a PIC32. The Pi just can't wake up fast enough so the PIC32 had to buffer thousands of CAN bus messages. Once the Pi was awake it became the SPI bus master to pull messages up from the PIC32 and write them with time stamps to a file. Although I initially roughed out the Pi software with Python I had to change to C to make it fast enough too. My application forked into two tasks and with a pipe, signaled to another application that took care of reading the files and shipping them off to the cloud via WiFi or CellNet. And like my project, I guess the Robot Arm Chris mentioned is also another example of where the RT is passed off to a dedicated processor while anything requiring 'OS' features like SSH are carried by the Linux system. Hard Real time isn't as important. After all, aren't we already seeing that with modules for Windows like the SmoothStepper and for Linux aren't most of the expansion cards intelligent enough to do the hard RT processing? In effect what the PRUs do on the BeagleBone? Just to bring this back to LinuxCNC... John ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
