Ian what files are needed? Forgive me if its in the read me. Thanks
On Fri, Sep 5, 2014 at 2:56 PM, paul swed <paulsw...@gmail.com> wrote: > Ian > Have not downloaded the info yet. > But I was surprised by the fact you were using LORAN sooo you must be in > Europe. Lucky you to have such a fine signal. > Great job on the tic. Now to go download the bits. > Thanks again. > Regards > Paul. > > > On Sun, Aug 31, 2014 at 10:26 PM, Tom Van Baak <t...@leapsecond.com> wrote: > >> Hi Iain, >> >> Thanks very much for posting, and for sharing the code. I know many of us >> are interested in how well modern CPU's or SBC's can be used as time >> interval, time stamping, and frequency counting instruments. I know the BB >> PRU's have been mentioned before on the list but it's really nice to see >> actual code and test results. >> >> About the hp 5370 -- realize that these are still 1000x more precise (on >> the order of tens of ps) than what a BB/PRU is capable of (on the order of >> tens of ns). But as you observe, they key point is -- for mid- to long-term >> measurement of free-running time/frequency standards you do not necessarily >> need ps-level measurement capability. Nanosecond, or even microsecond time >> resolution is more than enough to create comprehensive plots of time and >> frequency drift over the long-term. >> >> Again, thanks. >> >> /tvb >> >> ----- Original Message ----- >> From: "Iain Young" <i...@g7iii.net> >> To: "Discussion of precise time and frequency measurement" < >> time-nuts@febo.com> >> Sent: Sunday, August 31, 2014 1:24 PM >> Subject: [time-nuts] Poor Mans TIC (Using Beaglebone onboard PRU) >> >> >> > Hi Folks, >> > >> > As much as we all love our HP 5370B's, they are a tad expensive if you >> > want to monitor several PPS sources long term to ensure they are all >> > closely syncronised. >> > >> > In my case, I have three Austron 2100 LORAN receivers and a HP Z3816A >> > GPS receiver. I wanted to be able to compare each of their PPS outputs >> > with the PPS output of the Z3816A, as well as each other. >> > >> > Clearly, multiple 5370's would have been too expensive, not just for >> > initial outlay, but also ongoing electrical costs would not be helped! >> > >> > >> > However, the Beaglebone (Both White and Black variants) have two PRUs. >> > These are real-time units, with clocks that run at 200 MHz, and most >> > instructions complete in 1 clock cycle (5ns) >> > >> > So, I decided to write a TIC in the PRU Assembler to scratch my >> > particular itch. The current code waits for the "A" clock to go >> > high, and then counts until "B" goes high, resets it's counters, >> > and waits for "A" to go high again. >> > >> > It also keeps track of a "sequence" number for sanity's sake, and >> > onward processing. >> > >> > Since the Beaglebone's have two PRUs, I have written the code to run >> > on both at the same time, and use different GPIO pins, so you can >> > compare up two sets of two clocks, or two clocks with a common >> > reference. Pins are documented in README.txt >> > >> > Now, it's resolution is 20ns. However, it gets confused if the two >> > pulses are less than around 10-11uS apart. I -think- this is when >> > it sends the data back to the host processor via shared RAM. >> > >> > In my case, this is not an issue, as I can just slew the PPS from >> > the Austron's (or even use the Fixed PPS), but if you wanted to >> > compare two GPS receivers, then that would be an issue. >> > >> > >> > I'll have to look if there's a better way to do the shared memory >> > stuff (interrupts, signaling etc), or store multiple intervals and >> > send them all at once, although the current code seems pretty >> > tight. >> > >> > I'd like to have tried it with 1MHz, 5MHz, and even 10 MHz clocks, >> > as 20nS resolution will handle that, but I think I need to fix >> > the <11uS separation issue first. >> > >> > Then again, it was written to compare PPS's from different Austron >> > 2100's and GPS. It also took less than 24 hours from concept to >> > running :) >> > >> > If anyone wants it, the code is here here: http://hal.g7iii.net/bb_tic/ >> > >> > You will need the pasm compiler, and probably the am335x PRU package, >> > although there are (tiny) binaries there as well >> > Setup, Compile, and Running instructions are included in README.txt >> > >> > Oh, Sample output: >> > >> > PRU0: Seq No:848 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:849 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:850 Interval:11700 ns or 0.000011700 seconds >> > PRU0: Seq No:851 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:852 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:853 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:854 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:855 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:856 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:857 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:858 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:859 Interval:11680 ns or 0.000011680 seconds >> > PRU0: Seq No:860 Interval:11660 ns or 0.000011660 seconds >> > PRU0: Seq No:861 Interval:11660 ns or 0.000011660 seconds >> > >> > You can plainly see the Austron has a jitter of around +/-20 ns from >> > the GPS PPS (figures confirmed with the 5370). Slew was around 11.5us. >> > >> > I must wire up the other two Austron's but will need to build a new BB >> > image first :) Hope someone else finds the code useful. >> > >> > >> > Iain >> > _______________________________________________ >> > time-nuts mailing list -- time-nuts@febo.com >> > To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.