-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 6/1/2013 7:20 PM, Ed Nisley wrote: > On 06/01/2013 12:39 PM, Charles Steinkuehler wrote: >> I particularly like the acceleration control in LinuxCNC. It >> seems smoother than the Arduino code. > > At least on the Marlin firmware branch of the RepRap tree, the > interrupt handler switches from one-step-per-interrupt to > two/interrupt at 10 k step/s, then to four/interrupt at 20 k > step/s, with abrupt step timing changes. These pictures show the > step pulses to the X axis of my M2 during the ramp up to 450 mm/s > at 5000 mm/s^2: > > https://www.dropbox.com/s/llrx2ik6vlq4ne9/X%20Axis%20450%20mm-s%2050%20mm%20-%20100%20us-div%2041.9%20ms%20dly.png > > https://www.dropbox.com/s/z4w4mg6wklnhvpm/X%20Axis%20450%20mm-s%2050%20mm%20-%20200%20us-div%2019%20ms%20dly.png > > The top trace is the motor winding current, the bottom trace is the > Step pulse from the Arduino to the driver chip. The pulse clusters > on the right side show how a single interrupt produces multiple > steps, with the *average* rate remaining constant. However, speeds > over about 112 mm/s (on the M2, anyway) have irregularly spaced > Step pulses. > > I'm getting ready to disconnect the stock RAMBo board and hitch up > LinuxCNC through a Mesa card and some stepper driver bricks to the > M2; I think it'll be happier with regular Step pulses!
Great 'scope traces! The PRU step/dir code I wrote is currently running with a 10 uS task period. With a minimum of two task periods per step pulse, that puts the "marketing" maximum step frequency at 50 KHz, although I'd personally back that off by a factor of about 10 from the task period to insure smooth operation. So currently 10 kHz is easily possible, and since the PRU is currently about 85% idle (with a second PRU 100% idle), there's upside to get to about 40-50 KHz step rate with good performance via configuration and performance tweaking. It looks like as things stand now the PRU should easily run circles around the Marlin traces you showed. I'll try to capture something and post for comparison. ...and props for running a system at 450 mm/s! That rocks! :) - -- Charles Steinkuehler char...@steinkuehler.net -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlGqvXQACgkQLywbqEHdNFwmqwCgrIhkNI0Rd53oKe48E8HFZH3A iUYAoKYAE0Xswllxys4H82J2pYvsh7cW =oNF7 -----END PGP SIGNATURE----- ------------------------------------------------------------------------------ Get 100% visibility into Java/.NET code with AppDynamics Lite It's a free troubleshooting tool designed for production Get down to code-level detail for bottlenecks, with <2% overhead. Download for free and get started troubleshooting in minutes. http://p.sf.net/sfu/appdyn_d2d_ap2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
