[time-nuts] GPScon running on Raspberry Pi 3b

[Orin Eman]

On Thu, Jun 22, 2017 at 5:36 PM, Mark Sims <holrum at hotmail.com> wrote:

>
> The PI does have a couple of logic level serial ports on the expansion
> connector you can connect a level shifter two.  One port is normally the
> Linux serial console which you can configure to be a general purpose serial
> port (I've never used them, but others have).
>


Oh, that's fun on the Pi, especially the Pi3.  Here are my notes on the Pi3
from a different project.  If you're really lucky, they didn't change it
again.

QUOTE:

Well, they just couldn't make it backward compatible out of the box...

By default, ttyAMA0 is used for Bluetooth so there are more hoops to jump
through to wrest it away from the OS's grasp.  ttyS0 is now wired to the IO
pins which we could use if it worked correctly, but apparently its baud
rate depends on the cpu core frequency which is _variable_*.  Fortunately
there is a way of routing ttyAMA0 to the IO pins

As before, all references to ttyAMA0 need removing from /boot/cmdline.txt.

To disable bluetooth:

systemctl disable hciuart
Add "dtoverlay=pi3-disable-bt" to /boot/config.txt

Finally, perhaps unnecessary, use raspi-config to disable login on the
serial port.  (Serial under Advanced Options.)

* https://frillip.com/raspberry-pi-3-uart-baud-rate-workaround/
https://www.raspberrypi.org/forums/viewtopic.php?f=107&t=138223