stratum one on pi 4?

Hal Murray hmurray at
Sat Sep 21 01:09:31 UTC 2019

Are you trying to get the PPS via a serial port or via GPIO?

The serial ports on many SoC chips like the Pi only support read+write data, 
no modem control signals.  There are pins assigned for the modem control, but 
they are shared with other uses and most TTY hacking doesn't use them so they 
get used for other purposes.

The Pi-3 has ttyAMA0 used internally for BlueTooth.

My notes from setting up a Pi - they are mostly reminders.  I/you may have to 
poke around to figure out what each step is actually doing and/or why.


# PPS via gpio
  vi /boot/cmdline.txt
    remove the chunk(s) with ttyAMA0
  vi /boot/config.txt
    add new line: dtoverlay=pps-gpio,gpiopin=18
    pin 4 on Adafruit GPS HAT
  vi /etc/modules
    add new line: pps-gpio
  vi /etc/inittab
    run raspi-config Interfacing-Options/Serial
    comment out getty line for ttyAMA0 (at bottom)

# Pi-3 uses ttyAMA0 for BlueTooth
systemctl disable hciuart
Add "dtoverlay=pi3-disable-bt" to /boot/config.txt

These are my opinions.  I hate spam.

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