Andy Pugh wrote: > 2010/1/7 Flying Electron <sa...@flyingelectron.com>: > > >> So with a hypothetical setup of a mesa card, a brushless dc servo drive, >> and a 1000 CPR encoder, the mesa card's only job would be to read the >> encoder and report back to EMC and EMC would send the pwm signals out >> parallel port pins to the servo drive? >> > > You could do that (as long as your parallel port isn't full of Mesa > card) but it makes a lot more sense to do the PWM generation on the > Mesa card too. (Mhz rather than kHz PWM capability) > Ok, that makes more sense. I think I was confused because I didn't know that EMC2 could send commands to the mesa card to have the mesa card generate the pwm signal. So just to make sure I understand correctly, instead of EMC2 generating the pwm signal by toggling a parallel port pin, it's possible for EMC2 to send a command to the mesa board to set the duty cycle of a PWM output of the mesa card and the CPU on the EMC2 box only needs send a command to the mesa box whenever it wants to change the duty cycle of the PWM instead of constantly toggling the pin of the parallel port itself. And this happens once every servo period, which is around 1ms?
Looking at the Pico Systems PWM Brushless Servo Amplifier, it recommends a PWM frequency of at least 25khz, so assuming the parallel port could be driven fast enough the CPU would have to send data to the parallel port at least 50000 times a second to toggle a pin as opposed to sending 1000 commands a second to vary the generated PWM duty cycle. Is that kind of how it works? I think I'm slowly starting to understand how this is all supposed to work together... > Bear in mind that the Mesa (or similar) cards have a lot more pins > with more (and documented) current drive capability than a parallel > port too. > ------------------------------------------------------------------------------ This SF.Net email is sponsored by the Verizon Developer Community Take advantage of Verizon's best-in-class app development support A streamlined, 14 day to market process makes app distribution fast and easy Join now and get one step closer to millions of Verizon customers http://p.sf.net/sfu/verizon-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
