> > How come you send the velocity commands and not target positions? Size of > > the positioning data I assume? > > > Basically just following the LinuxCNC model of having the host be the > locus of control. This is the basic difference between buffered systems > like Mach and LinuxCNC. By having the LinuxCNC host be the controller > you gain a number of advantages: > > 1. The external hardware is simpler (and more uniform) > 2. The more complex parts of the control are located on a host > with basically unlimited memory and CPU capabilities so real time behaviour > is extensible by a large group of users/developers using standard tools. > 3. Specifically, returning actual position allows use of the following > error mechanism for tuning and robust fault detection without a side > channel of status information. >
I get the general idea. But I am still a little shy on the details. It sounds on a LPT port setup the host sends every individual step to the port. Now if the motor has an encoder LinuxCNC could read the position every 1ms and make it a host based closed loop system. And I get the appeal. But people are also using LinuxCNC with a BOB and Open Loop Steppers without an encoder. So it sounds like the feedback is missing there. Now for the Mesa card setup. IIUC LinuxCNC does not send every individual step over ethernet. Instead it sends motion controls commands. You said they are velocity commands. So it should be something along the lines of: "x+1000 steps in 1500ms" "y-100 steps in 500ms" On top of that the Mesa card will report back the position of the motors (steps from 0?) every 1ms to the host. Is that correct? cheers, Torsten _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
