Chris Morley wrote: > I switched to the .8 max velocity. It still errors. > It is still magnitudes worse in the negative direction. > I didn't have time to make scope screenshots nor > test very much. I can tomorrow if you would like.
I'm seeing something fishy here too, with ferrors when the [AXIS_?]MAX_VELOCITY approaches the stepgen's physical max. It may well be a bug in the driver, i need to look in to this more, but i got to thinking... The Hostmot2 firmware reports the clock rate that it's using for the stepgen timings, and the user's timing parameters from HAL (steplen, stepspace, etc) are converted to be ticks of that clock. The stepgen uses the hm2 "ClockLow" rate, which on the 5i20 is reported as exactly 33 MHz, but in reality is whatever the PCI bus runs at. It might be significantly different from 33 MHz, I've heard figures of 30-33 MHz as in-the-wild PCI clock rates. So... If the human asks for (for example) 1 microsecond StepLen+StepSpace, and the driver thinks the stepgen clock runs at 33,000,000 ticks/second, then it's going to ask for 33 ticks. But if the stepgen clock in reality runs at 30 MHz, then those 33 ticks will take 1.1 microseconds, and the max step rate will be 10% less than what everyone thinks. The human diligently computes the axis MAX_VELOCITY based on the 33 MHz stepgen clock, then gets ferrors when the actual setpgen clock is slower than that. Makes me want to calibrate the hm2 clocks at module load time... -- Sebastian Kuzminsky the sky calls to us -- carl sagan <http://www.youtube.com/watch?v=zSgiXGELjbc> ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
