Hi For $15 to $45 a number of places will sell you a uBlox receiver card that runs off of 5V and has an internal antenna. They are quite sensitive and have a timing output. They are plenty good enough for what you are trying to do. The practical issue is getting good enough GPS signals at an arbitrary location inside a house. To do that, you want a sensitive receiver.
No matter which receiver you get, they all put out fairly complex serial strings that need to be parsed to get the time information. For a wall clock the serial data “time of arrival” will be better than your eye can see. The PPS output is overkill, but this is Time Nuts. I would do the parsing with a small MCU. I doubt that an older FPGA will have enough “stuff” in it to do the job. You will need a few hundred bytes of RAM for buffering and not a whole lot else. There are thousands of different MCU’s that can / will / could / might do the job. Getting one already built up on a board for < $10 is pretty easy. Getting one on a board for < $3 is possible. Lots of choices. Bob > On Jul 10, 2016, at 11:55 PM, John Swenson <[email protected]> wrote: > > I'm thinking about converting a Nixie clock I built years ago into using GPS > for the time base. No real NEED, just for fun. > > The clock uses an FPGA for formatting and display, using the 60Hz line > frequency as the time base. The case is a single hollowed out block of walnut. > > I'm looking into a TU36-D400-020 receiver. This seems to be optimized for > timing purposes rather than navigation, it has 1PPS and 10KHz outputs. > > I'd be getting it from RDR Electronics, which says it it uses the Motorola > command set. This seems fine for me, it has the information I need, > specifically UTC time so I don't have to worry about leap seconds. > > I have a few questions about this receiver: > The data sheet lists two serial ports, but I don't see any information about > which to use. Are they identical, do I have to use one for some functions and > the other for other purposes? > > What are the serial port parameters? 9600-8-N-1? Or something else? > > Which is better to use, the 1PPS or the 10KHz? I can easily go either way. > The clock display just goes down to seconds so 1PPS would work. I could also > re-clock the 1PPS with the 10KHz. > > What antenna to use? I would prefer something mounted inside the case. It is > wood so an internal antenna will hopefully work. The board comes with a > pigtail but it is not SMA. > > Any other hints for using this? > > I've never done a GPS interface before so I'm not sure about how I calibrate > the time coming from the message over the serial port. Is it something like > "the time is such and such at the rising edge of the next PPS, or the > previous one? Or is there some other mechanism for calibrating when the > second changes on the display to something close to reality? > > I previously toyed with the idea of using an X72 rubidium oscillator just for > the bragging rights, but I would still need the GPS to get the time, I > decided the TU36 on its own is probably just fine. > > Thanks, > > John S. > > > _______________________________________________ > 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.
