Hi Charles I need to drive three axis, so three step/dir generators would be ideal. That data about the pru_period would be nice!
What is the main goal of using the PWM signals? Regards Maxi 2013/11/14 Charles Steinkuehler <[email protected]> > On 11/14/2013 2:10 PM, Maximiliano Fermín Córdoba wrote: > > > > My main goal is to test the beaglebone with linuxcnc in the worst > escenario > > so as to decide if it is capable of managing the whole system operation. > > Maybe the best option is to use an external stepgenerator and use the > 'bone > > only for the graphical interface and the gcode interpreter. Something > like > > sending through spi (or something like that) the actual movement and the > > external embedded system drive the steppers. > > > > So my actual drivers are driven with 2usec pulses and I was willing to > > generate reliable signals with a max frecuency of 50k. If the jitter is > > like the one Im facing now its useless. > > > > I would really appreciatte your guidance in configuring properly my > system. > > If you really want 2 uS wide pulses, you'll have to get the PRU task > period to be 2 uS or less. That's possible, but I wouldn't run that > fast with the default configuration. You can probably pretty safely > drop to 5 uS without issue (the 10 uS period is *VERY* conservative), > but 2 uS is pushing things without verifying the worst-case PRU task > period time. > > One thing I forgot to ask is how many channels of step/dir you are > trying to generate and if you are using the PWM channels. The fewer > tasks you have the PRU performing, the shorter you can dial the task > period. If you only need 3 step/dir generators, 2 uS is probably > reasonable with the existing PRU code, and it will dramatically improve > the jitter you're observing with 50 KHz steps. > > You can control the number of step/dir and PWM generators via the > hal_pru_generic command options when loading the driver (the parameters > should be fairly self explanatory), and you can add the pru_period= > parameter to set the task period to something shorter than the 10 uS > default. > > Let me know how many step/dir channels you need to run, and I'll try to > verify how long the PRU task takes to execute (and thus a safe > pru_period value). > > -- > Charles Steinkuehler > [email protected] > > ------------------------------------------------------------------------------ DreamFactory - Open Source REST & JSON Services for HTML5 & Native Apps OAuth, Users, Roles, SQL, NoSQL, BLOB Storage and External API Access Free app hosting. Or install the open source package on any LAMP server. Sign up and see examples for AngularJS, jQuery, Sencha Touch and Native! http://pubads.g.doubleclick.net/gampad/clk?id=63469471&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
