rpi3 and Adafruit GPS Hat

[Per olof Ljungmark]

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.
> 
> there's probably some good reason that this is a bad idea.

Depends on what precision you are after, but for lowest possible jitter
you need to use the uart, the difference is in magnitudes.

> On Sun, Jul 22, 2018 at 9:09 PM Per olof Ljungmark <peo at nethead.se
> <mailto:peo at nethead.se>> wrote:
> 
>     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.
>     >>
>     >> 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.
>     >>
>     >> What I need to achieve,
>     >>
>     >> - Stop the kernel to use the uart for console output (I have ethernet
>     >> and HDMI connected)
>     >
>     > No need.
>     >
>     > change your config.txt
>     >
>     > #dtoverlay=pi3-disable-bt
>     > device_tree_address=0x4000
>     > kernel=u-boot.bin
>     > enable_uart=1
>     >
>     > 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
>     >
>     > Remove the pi3-disable-dt in config.txt
>     > enable_uart=1 is needed.
>     >
>     >> VERY grateful if someone that knows better can give me a push in the
>     >> right direction for up to date information.
>     > ..
>     >
>     > This is assuming you use FreeBSD-12 (Head of tree)
>     >
> 
>     Yes, 12.0-CURRENT #2 r336461.
> 
>     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:
> 
>     http://freebsd.1045724.x6.nabble.com/Adding-a-GPS-Module-hat-shield-on-a-Raspberry-Pi-td6236680.html
> 
> 
>     _______________________________________________
>     freebsd-arm at freebsd.org <mailto:freebsd-arm at freebsd.org> mailing list
>     https://lists.freebsd.org/mailman/listinfo/freebsd-arm
>     To unsubscribe, send any mail to
>     "freebsd-arm-unsubscribe at freebsd.org
>     <mailto:freebsd-arm-unsubscribe at freebsd.org>"
> 
> 
> 
> -- 
> Kailua, Hawaiʻi
> US +1 (808) 728-3050
> UK +44 (020) 3286 2808
>