Peter, What type of counter do you use that can propagate a carry over 32 bits in 10 nsec? That's what you need to count at 100 MHz.
Ken Peter C. Wallace wrote: > On Sun, 20 Dec 2009, Kenneth Lerman wrote: > > >> Date: Sun, 20 Dec 2009 10:54:46 -0500 >> From: Kenneth Lerman <kenneth.ler...@se-ltd.com> >> Reply-To: "Enhanced Machine Controller (EMC)" >> <emc-users@lists.sourceforge.net> >> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> >> Subject: Re: [Emc-users] Interferometric leadscrew measurement/mapping? >> >> Yes, I have an Agilent 5517D which is a frequency stabilized two >> frequency laser that I got on Ebay. >> >> How fast can the counters on the 5I20 count? I would need a pair of >> perhaps 32 bit counters that can count at more than 4 MHz and can be >> read out "simultaneously". (Actually, copied into another set of >> registers at the same time and then transferred to the host before the >> next copy time). >> >> Ken >> > > The counters will count fast enough but with hostmot2 they are only 16 bits > wide (This should not be a problem at 4 MHz as the rollover rate would only > be > 64 Hz and servo thread sampling would likely be at 1 KHz or more). Its > possible to latch both counters simultaneously with the index (or probe) > input > so seem like you could do what required. > > Probably better would be to add a HostMot2 module for interferometer > counting, with common reset, 32 bit counters (maybe with difference > available) > and perhaps a relative phase register, (at 100 MHz sample rate you could get > ~15 degrees resolution of you 4 MHz reference) > > I would not mind doing the firmware (probably no more than a couple hours > work), but the HostMot2 driver would need to have support added for the > special counter > > >> Anders Wallin wrote: >> >>>> A laser interferometer is on my todo list. I've acquired all of the >>>> optics on ebay for a total of a few hundred dollars. I've built a power >>>> supply. The major part I'm missing is the counting and interpolating >>>> electronics with a computer interface. >>>> >>>> >>> Hi Ken, >>> >>> the heterodyne interferometers I have found described mostly use a >>> two-frequency laser which emits two orthogonal polarizations with >>> slightly (500kHz? or in your case 4 MHz) different frequency. Did you >>> find a Zeeman-stabilized two-frequency laser on ebay? Or are you >>> planning to DIY and put magnets around a normal HeNe tube? Sams Laser >>> FAQ has a description: >>> http://www.repairfaq.org/sam/laserchn.htm#chndzees >>> >>> The other method is to use an acousto-optic modulator to shift the >>> frequency of the light. But the papers I've found use two modulators, >>> and I only have one to spare right now... >>> >>> If I can either find a two-frequency HeNe or DIY with magnets then I'd >>> be interested in testing this, possibly with the m5i20 (already has >>> fpga code for fast encoder counters) for data acquisition. >>> >>> Anders >>> >>> ------------------------------------------------------------------------------ >>> 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 >>> >>> >> ------------------------------------------------------------------------------ >> 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 >> >> > > Peter Wallace > Mesa Electronics > > (\__/) > (='.'=) This is Bunny. Copy and paste bunny into your > (")_(") signature to help him gain world domination. > > > ------------------------------------------------------------------------------ > 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 > -- Kenneth Lerman 55 Main Street Newtown, CT 06470 203-426-3769 ------------------------------------------------------------------------------ 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
