README.md

piju-touchscreen

Touch-screen UI for https://github.com/nsw42/piju

Hardware setup

Additional hardware needed:

• The 7" touchscreen LCD: https://www.okdo.com/p/official-raspberry-pi-7-touch-screen-lcd/
• A case: https://thepihut.com/collections/raspberry-pi-screens/products/raspberry-pi-7-touchscreen-display-case-clear?variant=32291995353150

Cable up as per the Okdo instructions and put it in the case. Add power and the screen shows Alpine Linux.

Following the Okdo instructions left the screen upside down. Adding lcd_rotate=2 to usercfg.txt (see below) fixes that.

Note that this seemed quite electrically noisy, interfering with DAB radio reception when the screen was on. I've tried adding copper shielding tape to the inside of the case, which has helped a little.

Install the X environment

As root:

• setup-xorg-base

• apk add mesa-dri-vc4 mesa-dri-swrast mesa-gbm xf86-video-fbdev xfce4 xfce4-terminal

• mount -o remount,rw /media/mmcblk0p1

• Edit /media/mmcblk0p1/usercfg.txt, to add:

  dtoverlay=vc4-fkms-v3d
  gpu_mem=256
  lcd_rotate=2
  

• Create /etc/X11/xorg.conf:

  Section "Device"
    Identifier "default"
    Driver "fbdev"
  EndSection
  

• lbu commit -d

• reboot

Install the piju local UI

• Install dependencies. As root:

  apk add py3-gobject3 librsvg

• Download (or git clone) https://github.com/nsw42/piju-touchscreen

• pip install -r requirements.txt

Make the UI start automatically

There are several different ways to do this. One is to write a custom init script, and you'll find an example of this if you hunt in the history of this git repository.

The cleaner approach, though, is to configure automatic login for the piju user on the console, and for that user's login script to startx:

• As root:

  apk add util-linux

• Also as root, edit /etc/inittab so that the tty1 line reads as follows:

  tty1::respawn:/sbin/agetty --autologin piju --noclear 38400 tty1
  

• If you reboot at this point, you should be automatically logged in (to an ash prompt) as the piju user.

• As the piju user, create $HOME/.profile:

  if [ -z "${DISPLAY}" -a -z "${SSH_CONNECTION}" ]; then
          exec startx
  fi

• Note that many examples online will test $XDG_VTNR, but that env var is specific to systemd, which Alpine does not use. Testing $SSH_CONNECTION ensures that you can still ssh to the server to fix/update things.

• If you log out now, you should be automatically logged back in, and this time X should start automatically.

  • If X doesn't start, citing permission errors, check that you did sudo addgroup piju video
  • If keyboard/mouse/touchscreen aren't working, check that you did sudo addgroup piju input

• All that remains is to start the PijuUI when X starts.

• Note that this contains hard-coded paths for log files, which are specific to my configuration.

• Write a ~/.xinitrc file:

  #! /bin/sh
  
  startxfce4 &
  sleep 10
  exec $(dirname $0)/piju-touchscreen/run.sh

  TODO: This runs startxfce4 because the python application wasn't filling the screen otherwise. It shouldn't be necessary to run the window manager, though.