Case

A simple ply wood case for the Kaffeekasse

Required Hardware

• Raspberry Pi 3) (or later), ~40 Euro
• Touch-Display, e.g. Waveshare 10.1inch, ~100 Euro
• optional: Barcode Scanner, ~30 Euro
• optional: NFC Reader, e.g. ACR122U, ~30 Euro
• Power Supply (5V / 5A)

Case Construction

There exist two lasercut plans in Scalable Vector Graphics-Format for the Hardware mentioned above, using 4mm ply wood:

• Case for wall mount
• Case for wall mount with screws
• Case with stand

Assembly

Since the display does not support a software solution to disable the backround LED, a transistor controlled via RPi GPIOs replaces the LED switch on the background.

Software

• Raspbian (Buster) Lite as base, boot it and update all packages

  sudo apt update
  sudo apt dist-upgrade

• Setup HDMI Display according to the Waveshare Wiki: Add the following lines to /boot/config.txt

  hdmi_group=2
  hdmi_mode=87
  hdmi_cvt 1280 800 60 6 0 0 0
  hdmi_drive=1
  display_hdmi_rotate=2

• For faster startup, change/add following lines in /boot/config.txt

  disable_splash=1
  boot_delay=0
  dtoverlay=pi3-disable-bt

• Install the Chromium Browser, LightDM and libinput with

  sudo apt install chromium-browser lightdm xserver-xorg-input-libinput

• Enable autostart of the browser in kiosk mode by copying the provided file Xsession to /home/pi/.Xsession (mind the dot). Adjust the URL and monitor timeouts (30s) to your needs.
• Disable the mouse cursor in lightDM config /etc/lightdm/lightdm.conf by uncommenting and modifing the xserver-command line in the [Seat:*] section to

  xserver-command=X -nocursor

• Start raspi-config, change in 3 Boot Options / B1 Desktop / CLI to B4 Desktop Autologin and perform updates (8 Updates)
• To rotate touch input, copy the file 40-libinput.conf (originated from /usr/share/X11/xorg.conf.d/40-libinput.conf) to /etc/X11/xorg.conf.d/40-libinput.conf (create the xorg.conf.d directory first)
• Setup booting directly into X via sudo raspi-config and establish your network connection
• Install slock (suckless-tools) and copy the provided files backlight.sh and backlight.py to /opt/backlight.sh and backlight.service to /etc/systemd/user/backlight.serivce, reload (as user pi) systemd and enable the service to support LED backlight disabling during power saving

  systemctl --user daemon-reload
  systemctl --user enable backlight.service
  systemctl --user start backlight.service

• Reboot. You are good to go.
• To avoid the SD-Card to be worn out, enable Overlay FS by executing sudo raspi-config and selecting 7 Advanced Options / AA Overlay FS. Probably easier if the boot partition is kept writeable. You can remove the chromium directory (rm -rf ~/.config/chromium) and reboot.

Troubleshooting

Screen is not rotated

Disable the kms driver in /boot/config.txt:

#dtoverlay=vc4-kms-v3d

Chromium does not load the first tab (second tab works)

Issue: https://github.com/RPi-Distro/chromium-browser/issues/28

echo 'export CHROMIUM_FLAGS="$CHROMIUM_FLAGS --use-gl=egl"' | sudo tee /etc/chromium.d/egl

Backlight service: No access to /dev/mem. Try running as root!

Add the user to the gpio group:

sudo adduser kaffeekasse gpio