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List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 29 Nov 2019 06:52:01 -0000 On Fri, 29 Nov 2019, Peter Jeremy wrote: > On 2019-Nov-27 22:20:50 -0700, Ross Alexander wrote: >> An Adafruit "ultimate gps hat" (typical commercial hyperbole, sigh.) >> It's about $65 after you add the 40 pin molex connector, the >> micro-whatever to SMA cable, and the external amplified patch antenna. > > You can get a uBlox 7 or 8 module with a patch antenna and PPS output > for O($10). It should be possible to wire the serial data to the PL011 > UART and preserve the serial console UART but you'd to write a driver. Agreed. The hat spares you the wiring and mounting challenge. The s/w issues are why I'm running the GPS box on Debian. I do plan to go back and try it again on that same h/w using 12-stable at some point. I recall that some of the uBlox parts are designed for timing apps rather than navigation - they would be the ones to go with. > I have a metal roof and find putting the GPS module with a patch > antenna near a window (or even near an external wall) is sufficient. I have an identical (pi-2, ult hat, external patch antenna, debian) system running at work where I can get only a view of half the sky and it has significantly more jitter. A broader sky view gives more confidence in the position domain (more birds, and they are more spread out), which translates into lower time jitter. I'm arguing from a very small sample size here, of course. I would love to have a larger population to test. BTW, another *significant* source of jitter is the brand and age of the sd/mmc card used. As they age, the write speed decreases and block write latency gets less uniform; this shows up as system clock jitter in the loopstats. After a few years (3 or 4), the box becomes a complete falseticker and you need to replace the sd/mmc card. regards, Ross =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D Ross Alexander, (780) 675-6823 desk / (780) 689-0749 cell, rwa@athabascau.c= a 54.71593 N 113.30835 W Order is simply a thin, perilous condition we try to impose on the basic reality of chaos. -- William Gaddis, _J R_ -- This communication is intended for the use of the recipient to whom it is a= ddressed, and may contain confidential, personal, and or privileged informa= tion. Please contact us immediately if you are not the intended recipient o= f this communication, and do not copy, distribute, or take action relying o= n it. Any communications received in error, or subsequent reply, should be = deleted or destroyed. ---