Didier, Thanks. I doubt Hittite will send me a couple of samples for "this one and that one and oh that one", but you do raise a good point. I can always try! :)
With respect to fpga development boards, for this project I am all set! I am currently tinkering with these two boards: http://www.digilentinc.com/Products/Detail.cfm?Prod=NEXYS2 http://www.digilentinc.com/Products/Detail.cfm?Prod=ATLYS Both have one of those ez-usb fx2 controllers from cypress (cy7c68013a), which I find easy to work with under linux. Plus I already had verilog modules from some older projects that take care of the usb fifos on the fpga side. As for processor, currently I use a picoblaze softcore which works for both the spartan-3 and spartan-6. So I only have to write code for that once... My remarks regarding the tqpf-100 package was for the benefit of those who might be looking for something to put in a DIY counter and want to be able to solder it themselves. Since I'm already using these development boards for other stuff as well, I thought it would be fun to see how far one can take these things timing resolution-wise... I am not familiar with the Actel parts. Do you happen to know what kind of timing granularity is possible with the carry chain or similar structures on those Actels? regards, Fred --- On Thu, 1/6/11, [email protected] <[email protected]> wrote: > From: [email protected] <[email protected]> > Subject: Re: [time-nuts] No State Of The Art Counter > To: "Time-Nuts" <[email protected]> > Date: Thursday, January 6, 2011, 8:25 PM > Fred, > > Good luck on your project, it sounds exciting. > > I have been able to get a couple of samples for free from > Hitite. That was several years ago (before the > recession...) > > Regarding FPGA, Actel has a demo board for their > SmartFusion device (big flash-based FPGA + Cortex M3 > processor + 256k program flash separate from the FPGA on the > same chip, not a soft core) which has USB slave and Ethernet > ports for about $200 in qty 1. There is also a smaller FPGA > (ProASIC+) on the board, not sure what it is used for? I > have one of these boards, but I have not done anything with > it yet. It is a nice board full of potential... The chip is > in a BGA package, but if you use this board, you don't need > to add much, just the clock and input circuits. > > Didier KO4BB > > Sent from my Verizon Wireless BlackBerry > > -----Original Message----- > From: Tijd Dingen <[email protected]> > Sender: [email protected] > Date: Thu, 6 Jan 2011 11:02:12 > To: <[email protected]> > Reply-To: Discussion of precise time and frequency > measurement > <[email protected]> > Subject: [time-nuts] No State Of The Art Counter > > To whom it may concerns, > > Currently I am building a DIY frequency counter. Since this > is my first serious counter project I am trying to keep > things simple, hence It Will Not Be State Of The Art. Maybe > a not-too-difficult hobby level counter will be of interest > to some, so I'd thought I'd post here... > > The architecture in a couple of bulletpoints: > - fpga based as much as possible to keep the parts count > down > - coarse counters running at max 200 MHz for now > - interpolation is done using TDC's. The TDC's look > suspiciously much like tapped delay lines and are > implemented inside the fpga, using mainly the carry chains. > - 10000 continuous time stamps per second > - 500 ps timestamp resolution. And with resolution I mean > the smallest resolvable thingy (related to bin size), not > precision nor accuracy. > > That 500 ps is conservative. I intend to do better than > that, but just to give some idea of the starting point... > The main thing for now is to get a handle on the DNL of the > TDC. > > I am currently playing around with some designs in a > spartan-6 and a spartan-3e. The spartan-6 design has more > promise resolution wise, but it is also not very hobby > friendly (bga package). So if this is ever to be built using > hobby level soldering skills it will be spartan-3e. The 250k > gates devices are available in tqfp-100 package which is > doable IMO. > > The timestamps are transmitted over usb to the pc for > number crunching. The idea is to do some curve fitting to > get a frequency estimate, computate Allan Deviation, and do > the obligatory plots. With regard to Allan Deviation, as > long as I make sure the measurements have zero dead time, I > can compute Allan Deviation using the raw time stamps, > right? > > Also note the glaring lack of a prescaler. This can and > will be added at a later date to extend the range of the > counter. For now I just want to get the basics working > properly first. On the subject of prescalers, does anyone > know where to order Hittite parts in low quantities? I > noticed on hittite.com you can place an order but if I > understand correctly that is only for 10+. Which is probably > great if you do a group buy, but not if I want to try out 3 > of those, 2 of those, etc... > > Another question for those that have already done this ... > suppose you have a "good" 10 MHz (OCXO, GPSDO, WhateverO) > and want to use that for your reference counter. What is a > reasonable low cost method to end up with a 200 MHz clock in > a spartan-3e and a 500 MHz clock in a spartan-6? I am > currently using the fpga's internal dcm but the added jitter > is considerable. > > Since I am a newbie when it comes to this time stuff, no > doubt there will be plenty of you that have more experience > with implementations of counters ... so what are regular > pitfalls I should be aware of? > > Thank you for your time, > Fred > > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
