---
title: a kiosk for my kitchen
date: 2020-08-05
---
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	In a corner of my kitchen, there is a little touchscreen interface for "kitchen things".
	Below is why I have that, what it's made of, and how it works.

	## Why?

	There are two main reasons why I want a kitchen kiosk unit:

	- I have too Internet of Things things in my kitchen, and getting my phone out to control it is annoying.
	- I want to record when I drink coffee, when I snack, etc, and getting my phone out to log that is annoying.

	## What?

	I already have a Raspberry Pi in the Kitchen to provide [WiFi](/wifi) and [audio](/multi-room-audio), so extending that is a good start.
	I could create a custom control panel with physical buttons, but adding a touchscreen to an existing unit is easier.

	So I got the official Raspberry Pi touchscreen, a stand for the screen, and voila, the hardware side is done.

	## How?

	Continuing with the theme of minimal effort for maximum gain, I decided to use my existing skills and implement the UI with a website:

	- I can hack up a webserver pretty fast.
	- Chromium has a kiosk mode.
	- Chromium can handle rendering and input.

	This means that all I need to do is make Chromium start on boot, and write a simple webserver!

	From a standard Raspbian image, install the relevant softwares:

		$ sudo apt install chromium lightdm xinput

	Then, create a user to run Chromium, here called `kiosk`:

		$ sudo adduser kiosk

	Next, we're going to use `lightdm` to bring up Xorg and automatically log in as `kiosk`:

		$ cat /etc/lightdm/lightdm.conf
		[Seat:seat0]
		type=local
		pam-service=lightdm-autologin
		autologin-user=kiosk
		autologin-user-timeout=0
		xserver-command = X -nocursor

	For our `kiosk` user to set the brightness, we need to add a `udev` rule to make it writeable:

		$ cat /etc/udev/rules.d/50-backlight.rules 
		SUBSYSTEM=="backlight",RUN+="/bin/chmod 666 /sys/class/backlight/%k/brightness /sys/class/backlight/%k/bl_power"

	Finally, `kiosk`'s graphical login script (`~/.xsession`) will set the brightness and display-sleep modes, then start Chromium:

		$ cat /home/kiosk/.xsession
		readonly standby_seconds=60
		readonly suspend_seconds=60
		readonly off_seconds=60

		readonly brightness_percent=50

		# TODO: write a custom UI webserver.
		readonly website="https://ethulhu.co.uk"

		xset dpms "${standby_seconds}" "${suspend_seconds}" "${off_seconds}"
		echo "${brightness_percent}" > /sys/class/backlight/rpi_backlight/brightness
		exec chromium --noerrdialogs --kiosk --incognito "${website}"

	Reboot the Raspberry Pi, and it should automatically log in as `kiosk` and run the website.
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