PPS GPIO with Buildroot image on Raspberry Pi 3












1















I'm a beginner with 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:




  • Add dtoverlay=pps-gpio,gpiopin=20 to /boot/config.txt.

  • Add pps-gpio to /etc/modules.


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 make nconfig:




  • Using kernel branch rpi-4.14.y-rt from github.com/raspberrypi/linux


  • systemd as init system

  • /dev management using udev (from systemd)


  • Target packages -> Hardware handling -> pps-tools activated


(I think that is all the changes I made, but I might have forgotten something..)



In the 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 /dev/ppsX?



Thanks!






linux udev buildroot device-tree







share|improve this question



























    1















    I'm a beginner with 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:




    • Add dtoverlay=pps-gpio,gpiopin=20 to /boot/config.txt.

    • Add pps-gpio to /etc/modules.


    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 make nconfig:




    • Using kernel branch rpi-4.14.y-rt from github.com/raspberrypi/linux


    • systemd as init system

    • /dev management using udev (from systemd)


    • Target packages -> Hardware handling -> pps-tools activated


    (I think that is all the changes I made, but I might have forgotten something..)



    In the 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 /dev/ppsX?



    Thanks!






    linux udev buildroot device-tree







    share|improve this question

























      1












      1








      1








      I'm a beginner with 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:




      • Add dtoverlay=pps-gpio,gpiopin=20 to /boot/config.txt.

      • Add pps-gpio to /etc/modules.


      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 make nconfig:




      • Using kernel branch rpi-4.14.y-rt from github.com/raspberrypi/linux


      • systemd as init system

      • /dev management using udev (from systemd)


      • Target packages -> Hardware handling -> pps-tools activated


      (I think that is all the changes I made, but I might have forgotten something..)



      In the 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 /dev/ppsX?



      Thanks!






      linux udev buildroot device-tree







      share|improve this question














      I'm a beginner with 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:




      • Add dtoverlay=pps-gpio,gpiopin=20 to /boot/config.txt.

      • Add pps-gpio to /etc/modules.


      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 make nconfig:




      • Using kernel branch rpi-4.14.y-rt from github.com/raspberrypi/linux


      • systemd as init system

      • /dev management using udev (from systemd)


      • Target packages -> Hardware handling -> pps-tools activated


      (I think that is all the changes I made, but I might have forgotten something..)



      In the 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 /dev/ppsX?



      Thanks!






      linux udev buildroot device-tree




      linux udev buildroot device-tree






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      asked Mar 4 at 16:05









      Isak T.Isak T.

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