Date: Mon, 23 Jul 2018 11:11:12 -0400 From: Ralph Smith <ralph@ralphsmith.org> To: Per olof Ljungmark <peo@nethead.se> Cc: David Cornejo <dave@dogwood.com>, freebsd-arm <freebsd-arm@freebsd.org> Subject: Re: rpi3 and Adafruit GPS Hat Message-ID: <72A10F81-7BC3-4B4F-BDC0-26A47DB04ABD@ralphsmith.org> In-Reply-To: <7a14173c-cc28-6dc7-3787-a5b77a396b30@nethead.se> References: <47f49a55-66b0-1c02-4530-4701a3bd0c43@nethead.se> <20180718170157.GA40221@night.db.net> <ba31ee27-1d17-8616-96b2-b982268f0dc2@nethead.se> <CAFnjQbt395y4xyHEp52GAHW9X9bHvdCAT9q-gKA2--RvQvqTtA@mail.gmail.com> <7a14173c-cc28-6dc7-3787-a5b77a396b30@nethead.se>
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Sent from my iPhone >> On Jul 23, 2018, at 5:40 AM, Per olof Ljungmark <peo@nethead.se> wrote: >>=20 >> On 07/23/18 10:46, David Cornejo wrote: >> this might be a little blasphemous, but for grins I tried an Oncore with >> PPS to a GPIO and running the serial through a TTL-USB serial cable and >> that seems to work ok. >>=20 >> there's probably some good reason that this is a bad idea. >=20 > Depends on what precision you are after, but for lowest possible jitter > you need to use the uart, the difference is in magnitudes. But he=E2=80=99s not running the PPS through the USB serial port, it is goin= g directly to GPIO. Correct me if I=E2=80=99m wrong here, but once ntpd lock= s to the PPS there is no real difference between the two. I=E2=80=99m runnin= g that exact scenario here with two Pis, both Model 2. One has an Adafruit G= PS HAT directly attached, and the other has the GPS connected to a USB-TTL s= erial adapter, with the PPS connected to the GPIO. Both sync to PPS with the= offset typically around 4 =CE=BCs and jitter around 2 =CE=BCs. I may try it= with an Oncore I have on hand but that will have to wait a month or so for o= ther things to settle down.=20 Ralph >> On Sun, Jul 22, 2018 at 9:09 PM Per olof Ljungmark <peo@nethead.se >> <mailto:peo@nethead.se>> wrote: >>=20 >>>> On 07/18/18 19:01, Diane Bruce wrote: >>>> On Wed, Jul 18, 2018 at 05:10:16PM +0200, Per olof Ljungmark wrote: >>>> Being a complete newbie to arm I thought a nice project would be to >>>> build a NTP server with the parts in the subject line. >>>>=20 >>>> Unfortunately I have almost no idea where to start, it seems >> FreeBSD for >>>> arm have shifted around quite a bit, almost none of the googled >> pages I >>>> find has relevance, and to add insult to injury, the Pi project >>>> apparently shifted the serial ports around for the Pi3. >>>>=20 >>>> What I need to achieve, >>>>=20 >>>> - Stop the kernel to use the uart for console output (I have ethernet >>>> and HDMI connected) >>>=20 >>> No need. >>>=20 >>> change your config.txt >>>=20 >>> #dtoverlay=3Dpi3-disable-bt >>> device_tree_address=3D0x4000 >>> kernel=3Du-boot.bin >>> enable_uart=3D1 >>>=20 >>> This moves the console port to the less capable micro uart port >>> this will free up the good uart (the pl011 device) as /dev/ttyu0 >>>=20 >>> Remove the pi3-disable-dt in config.txt >>> enable_uart=3D1 is needed. >>>=20 >>>> VERY grateful if someone that knows better can give me a push in the >>>> right direction for up to date information. >>> .. >>>=20 >>> This is assuming you use FreeBSD-12 (Head of tree) >>=20 >> Yes, 12.0-CURRENT #2 r336461. >>=20 >> Unfortunately your advice did not solve the problem, when the hat is >> attached it sends NMEA sequences to the u-boot loader making it >> impossible to boot further, just like it is described in this thread: >>=20 >> http://freebsd.1045724.x6.nabble.com/Adding-a-GPS-Module-hat-shield-on= -a-Raspberry-Pi-td6236680.html >>=20 >>=20 >> _______________________________________________ >> freebsd-arm@freebsd.org <mailto:freebsd-arm@freebsd.org> mailing list >> https://lists.freebsd.org/mailman/listinfo/freebsd-arm >> To unsubscribe, send any mail to >> "freebsd-arm-unsubscribe@freebsd.org >> <mailto:freebsd-arm-unsubscribe@freebsd.org>" >>=20 >>=20 >>=20 >> --=20 >> Kailua, Hawai=CA=BBi >> US +1 (808) 728-3050 >> UK +44 (020) 3286 2808 > _______________________________________________ > freebsd-arm@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-arm > To unsubscribe, send any mail to "freebsd-arm-unsubscribe@freebsd.org"
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