> On Nov 28, 2014, at 9:18 PM, Angus <[email protected]> wrote: > > > > > On Fri, 28 Nov 2014 08:57:37 -0600, you wrote: > >> Hi >> >>> On Nov 28, 2014, at 7:04 AM, Li Ang <[email protected]> wrote: >>> >>> The TDC-GP22 is the best choise for me at the moment. Since I am not a >>> hardware guy, simplicity is important. It's very cheap in China(About 3$ >>> for each piece ). >> >> Which is a very good reason to play with it > >> >>> >>> >>> TDC-GP22 has 2 modes and 3 trigger inputs (start, stop1, stop2). The min >>> time between start and stop is 3.5ns. max time is about 2.4us.(0 to 2.4 us >>> between stop channels). >>> Time resolution is 90ps, or 45ps in double_res mode(1 stop input only), and >>> 22ps in quard_res mode(1 stop only) >> >> All of which is *plenty* good enough to make a decent counter. That assumes >> that they are talking about accuracy (even 1 sigma) rather than just the >> resolution of the LSB. Specs are often confusing on parts like this. > > Hi , > > Unfortunately the 22ps etc is just resolution and there is also a fair > bit of noise - some typical SD's are given in the data sheet which > vary from 35 to 72 ps depending on the settings, and that only covers > part of the range. 60ps RMS noise is also mentioned. > > The nominal clock input is 2-8MHz, but the 22ps range is only > available for clocks <6MHz, and not in Mode1 which is being used. > > Should still be enough to give most counters a workout.
Hi As long as the one sigma point is below 100 ps, that’s not a disaster for turning it into a counter. It’s not going to beat out a SR 620, but it’s still a very respectable device. Being able to do it all with a handful of parts and at 1 to 3% of the cost of a new counter is pretty impressive. Assuming that the counter timebase is 10 MHz, a clock into the chip of 5, 3.333, or 2.5 MHz could be done quite easily. It sounds like they all would hit the 2 to 8 MHz range needed. Bob > > Angus. > > > >>> The biggest problem I met: >>> If you trigger start first, 100ns later stop1, another 100ns later >>> stop2.Get the result of stop1-start and stop2-stop1. You will find >>> stop1-start is very unstable(+-2% level) and stop2-stop1 is stable(+-0.1% >>> level ). Dont know if it's my problem or theirs. >> >> This may be the resolution / accuracy thing I mentioned above. Dont give up >> quite yet though. >> >>> >>> Here is the configuration of it (the document is very bad, took me 3 weeks >>> to play with these 6 registers to get it work as I expected) and schematic. >> >> Gee > that sounds like the documentation on a LOT of parts these days > . Its also what keeps people from trying this sort of thing. >> >> A few hardware questions: >> >> 1) What frequency is the crystal at? (can you drive the chip from an OCXO?) >> >> 2) Is there more bypassing on the circuit than shown? (If not, add some >> more). >> >> 3) How confident are you of your input signal? (can you check it with a >> known good counter?) >> >> 4) Have you tried jumping the 10 ohm resistor on the regulator output? (it >> may not be helping things > ) >> >> >> A full counter will have a bit more stuff than just this chip. I think >> getting this part working *before* you work on the rest of it is a very good >> idea. One small piece at a time > . >> >> Bob >> >> >> >>> Register_0 = 0x00c42700, >>> Register_1 = 0x19498000, >>> Register_2 = 0xe0000000, >>> Register_3 = 0x00000000, >>> Register_4 = 0x20000000, >>> Register_5 = 0x10000000, >>> Register_6 = 0; >>> >>> >>> ? >>> >>> 2014-11-28 0:20 GMT+08:00 Tom Van Baak <[email protected]>: >>> >>>> Your project sounds wonderful. The TDC-GP22 has been mentioned only a few >>>> times over the years and I keep waiting for someone to post actual results >>>> from this chip, or better yet -- schematics, photos, and source code. >>>> >>>> >>> <tdc_gp22.GIF>_______________________________________________ >>> 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. _______________________________________________ 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.
