Kiosk

Turns a Raspberry Pi into a simple browser kiosk. A Go program controls a full-screen Chromium browser.

Preparation

1. Configure the OS image using the Raspberry Pi Imager:

   • Set hostname
   • Enable SSH
   • Configure a non-default user
   • Configure WLAN
   • Set the locale

2. After first boot, use raspi-config to:

   • Auto-boot into the graphical environment without asking for login credentials
   • Disable screen blanking

Kiosk Controller

The official touch screen makes a great secondary display for the kiosk-controller. Add or change the following lines in /boot/config.txt:

• Rotate the touchscreen by 180°:

  lcd_rotate=2
  

• Switch to FKMS mode:

  dtoverlay=vc4-fkms-v3d
  

  Make sure it's fkms, and not kms.

Config File

The URL of the browser is described in a YAML file that is passed as argument or via STDIN to the kiosk binary. If multiple entries are present, they will be opened as browser tabs and switched between every --interval; e.g. 10s.

Example:

- name: org
  script:
    - go: https://example.org
    - click: //p/a
- name: com
  script:
    - go: https://example.com
- name: net
  script:
    - go: https://example.net

TODO

• Deal with default values of controller.StatusUpdate - we don't want to send IsTabSwitching = false just because we did not know the current value

  • pointers (and skip nil pointers)
  • always query everything (maybe not ideal)

• At page load, set initial status of display power

• If displays are powered off, power-up the controller if touched (catching a click in any part of the page)

• Update the status of the power checkbox if changed on the server side

• stream image updates (no need to reload images)

• keep updating screenshots while switching is paused (may be impossible)

• make the current page the one shown when loading the controller

• add another service to run the kiosk controller on the touch screen:

  $ chromium-browser --kiosk http://localhost:8011

• re-configure tab switching time in the controller

• deploy using pipeline

• test pages for presence of some element, otherwise close tab and restart (e.g. when authenticated session expires)

• refresh pages that are not self-refreshing (e.g. reload)

  • also useful as HTTP command

• configure lcd_rotate=2 and dtoverlay=vc4-fkms-v3d via Ansible

• unclutter -idle 0.5 -root & if needed

• splash screen at boot

• Turn displays on and off via HTTP or cron:

  # Touch Screen (primary monitor)
  $ vcgencmd display_power 0 0
  $ vcgencmd display_power 1 0
  
  # HDMI
  $ vcgencmd display_power 0 2
  $ vcgencmd display_power 1 2

  Alternatively:

  • Touchscreen

    $ sudo zsh -c "echo 1 > /sys/class/backlight/rpi_backlight/bl_power" # off
    $ sudo zsh -c "echo 0 > /sys/class/backlight/rpi_backlight/bl_power" # on

  • HDMI (2 is the HDMI port; use tvservice --list to list)

    $ tvservice -o -v 2
    $ tvservice -p -v 0

Deployment

Build the kiosk binary

For the Raspberry Pi 4, this is

$ GOARM=7 GOARCH=arm GOOS=linux go build

Prerequisites on the Deployer's Workstation

• Make sure you have a recent Ansible installation:

  $ brew install ansible

  Replace brew with yum or apt-get, depending on your OS.

• Install the required Ansible roles:

  $ ansible-galaxy install -r roles.yml

• Update inventory.yml with the host(s) to deploy to

Deploy

Run the playbook:

$ ansible-playbook playbook.yml