Date: Fri, 4 Mar 2016 10:54:14 -0600 From: Karl Denninger <karl@denninger.net> To: freebsd-stable@freebsd.org Subject: Re: PPS input on a generic GPIO pin on Raspberry Pi. Message-ID: <56D9BDB6.6040903@denninger.net> In-Reply-To: <8C90C80B-AC5F-4B12-8E84-84193B8C55C4@pean.org> References: <8C90C80B-AC5F-4B12-8E84-84193B8C55C4@pean.org>
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[-- Attachment #1 --] On 3/3/2016 12:57, Peter Ankerstål wrote: > Hi! > > I have sort of exactly the same question as Erik: > http://lists.freebsd.org/pipermail/freebsd-questions/2014-July/259055.html > > I have bought a https://learn.adafruit.com/adafruit-ultimate-gps and want to use the PPS output to discipline my clock. > > But the only source of information on how PPS works in FreeBSD I could find is this: https://docs.freebsd.org/doc/8.0-RELEASE/usr/share/doc/ntp/pps.html and it clearly states the two ways to provide a PPS signal. "The PPS signal can be connected in either of two ways: via the data carrier detector (DCD) pin of a serial port or via the acknowledge (ACK) pin of a parallel port” > > Since the Pi doesn’t have any DCD pin i would like to use a generic GPIO for this. There is a linux kernel module for this: http://lxr.free-electrons.com/source/drivers/pps/clients/pps-gpio.c?v=3.6 GPIO is supported on the Pi, I'm using it on 11-Current on my home control software to drive relays on my pool hardware (e.g. valves, heater, VFD motor drive, etc) and it is working very well. I don't believe tapping into that at the kernel level to expose a pps signal (e.g. on /dev/pps or something of the like) would be very difficult at all, since the low-level driver capability is already present. If I get some free time I'll dig around a bit and see if I can cobble something up. It's of some interest to me as well since I have a GPS clock here that currently talks to a serial port on an Intel-based machine and being able to move that to a $35 "appliance" for NTP using the Adafruit setup looks sort of attractive given that the Pi plus the module would be under $100 all-in. -- Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ [-- Attachment #2 --] 0 *H 010 `He 0 *H _0[0C)0 *H 01 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1"0 *H Cuda Systems LLC CA0 150421022159Z 200419022159Z0Z1 0 UUS10UFlorida10U Cuda Systems LLC1 0 UKarl Denninger (OCSP)0"0 *H 0 X@vkY Tq/vE]5#֯MX \8LJ/V?5Da+ sJc*/r{ȼnS+ w")ąZ^DtdCOZ ~7Q '@a#ijc۴oZdB&!Ӝ-< ? HN5y 5}F|e f"V لio74zn">a1qWuɖbFeGE&3(KhixG3!#e_XƬ Ϝ/,$+;4y 'Bz<qT9_?rRUpn5 Jn&Rx/p Jyel*pN8/#9u/YP EC)TY>~/˘N[vyiDKˉ ,^" ?$T8 v& K%z8C @?K{9f`+@,| Mbia 007++0)0'+0http://cudasystems.net:88880 U 0 0 `HB0 U 0, `HB OpenSSL Generated Certificate0 U -h\Ff Y0 U #0$q}ݽʒm50 U 0karl@denninger.net0 *H Owbabɺx&Uk[ (Oj!%p MQ0I!#QH}.>~2&D}<wm_>V6 v ]f>=Nn+8;q wfΰ/RLyUG#b}n!Dր _up|_ǰc/%ۥ nN8:d;-UJd/m1~VނיnN I˾$tF1&}|?q?\đXԑ&\4V<lKۮ3%Am_(q -(cAeGX)f}-˥6cv~Kg8m~v ;|9:-iAPқ6ېn-.)<[$KJtt/L4ᖣ^Cmu4vb{+BG$M0c\[MR|0FԸP&78"4p# }D Z9;V9#>Sw"[UP710001 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1"0 *H Cuda Systems LLC CA)0 `He M0 *H 1 *H 0 *H 1 160304165414Z0O *H 1B@y oc=2E a'A{BkB|HoQ^2YEfeQiھ+:9k):20l *H 1_0]0 `He*0 `He0 *H 0*H 0 *H @0+0 *H (0 +71001 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1"0 *H Cuda Systems LLC CA)0 *H 101 0 UUS10UFlorida10U Niceville10U Cuda Systems LLC1 0UCuda Systems LLC CA1"0 *H Cuda Systems LLC CA)0 *H v11CtQ N=}dO( >kU\ҪQP<3ȵq@w?c-G J(kVa ɏ"| ҵ4q;]tAV8oK%UBbNRiLix\m9 cl2IDR}(1rt GLj at8o _dYr\,RЄl ` YpGoua eS[0xeHU/L(R H&__$>׃B {$C dr&NNG{CeLb)jJqQ/tS Ð]W&i]Ni0^2pC+0ɎbN5Ԣ i%/<nރ(ѢҰ إtFvfLV \_qm-;U@֬!z*Rnb' ѢHYurs!k/gg
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