I using Buildroot trying to build a Linux image for the Raspberry Pi 3 in which I have access to pulse-per-second (PPS) inputs on one of the GPIO pins.
First off, I have tried this with the standard Raspbian distribution and got it to work with the following changes:
I then get an entry
/dev/pps0 and when connecting a wire with PPS signal to physical pin 38 on the RPi3 and running
pps-test /dev/pps0 I get the expected one signal per second.
So far so good.
Now I would like to recreate this with my own image built with Buildroot. I'm using the default
configs/raspberrypi3_64_defconfig configuration, but with the following changes in
- Using kernel branch
systemdas init system
/dev management using udev (from systemd)
(I think that is all the changes I made, but I might have forgotten something..)
sdcard.img which I get as output I see the file
pps-gpio.dtbo in the boot partition. I add the line
dtoverlay=pps-gpio,gpiopin=20 to the file
config.txt. I also add the line
pps-gpio to a file named
pps.conf which I put in
/etc/modules-load.d on the file system.
When I boot the system I get no entry
/dev/ppsX but when I run
lsmod I get (among others):
pps_gpio 16384 0
pps_core 20480 1 pps_gpio
Does this mean the
dtoverlay has been correctly loaded? What can I try in order to get an entry in