Hi Sam, Nice. But it does seem to support my premise on isolating LinuxCNC from the hardware control.
For example, way back a Pentium 386-66 with WIN-95 and MACH2 CNC was able to do this at 25KHz stepping. A BeagleBone Black with Machine Kit has PRUs to do the stepping and it's what, 4 years older than a RPi4? You’ve already shown that for a 1GHz+ LinuxCNC system that with an external Ethernet Hardware engine you can now get faster stepping rate . But only 10K steps/second on a 1GHz+ Pi? Since very slow PCs with limited memory could do this as well as the slower PRU processors on the BBB, I'd venture a guess that if a Pi4 can't do at least 50kHz stepping while also doing trajectory planning and screen updates there is something really 'off' with LinuxCNC. Maybe too many hardware abstraction layers? If I do the math. The RISC processors generally run one instruction per clock cycle and if that's really true there are 20,000 CPU cycles between each step at 50kHz. Coming from the embedded world where I work that’s huge. And generally the trajectory planners create FIFO buffers that hold a step and a direction bit for 4 axis in one byte. Each byte, sent out at 50Hz, either has a step signal nor not. At the end of the 5uS step pulse time as you said, the step levels are set off again. So as long as you can keep the buffer filled it's the interrupt routine that places it out to a parallel port. And filling the buffer is the job of the trajectory planner which does the co-ordinated accel, velocity, decel for all axis to be able to maintain a specific feed rate in 3 or 4 dimensions. I'd say being able to 10kHz stepping and being happy with that might be setting the bar very very low. BTW, I really do enjoy your videos. John Dammeyer > -----Original Message----- > From: Sam Sokolik [mailto:samco...@gmail.com] > Sent: February-16-20 3:27 PM > To: Enhanced Machine Controller (EMC) > Subject: [Emc-users] RPI4 is pretty close to a decent machine control > solution... > > software stepping... > > https://www.youtube.com/watch?v=LKjNOVHhHio > > Ethernet > > https://www.youtube.com/watch?v=2SEB7TuCUR0 > > I don't have an spi solution to try.... > > sam > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
