DashD

Lightweight daemon for Raspberry Pi driven kiosks

Features

• software control for screen buttons (power, source, menu, plus, minus)
• lighting integration with Artemis-RGB (UDP and HTTP support)
• website display using Chromium based browser
• control via HTTP server

Display

On startup DashD will create a browser window with the specified position and size, which can be changed later over HTTP. If the window is closed, DashD will exit.

CLI Flag	Default	Unit
display_enabled	true	Bool
browser_path	"/usr/bin/chromium-browser"	String (Path)
default_url		String (URL)
window_x	0	UInt (Pixel)
window_y	0	UInt (Pixel)
window_width	1920	UInt (Pixel)
window_height	1080	UInt (Pixel)

Lighting

DashD can drive a single addressable LED strip with WS281X LEDs (any GRB LEDs should work). On most Raspberry Pi GPIO 12, 18, 40, and 52 can be used for connecting the data line of the LED strip. However if you are using Model B+, 2B or 3B only GPIO 12 and 18 are supported due to a hardware limitation.

CLI Flag	Default	Unit
lighting_enabled	true	Bool
ledstrip_pin	18	UInt (GPIO)
ledstrip_length	100	UInt (Count)

Screen

DashD virtualizes the buttons of the screen, so they can be remote controlled via the HTTP server. The GPIOs should be connected to transistors in a way that a high output corresponds to pressing down the button.

CLI Flag	Default	Unit
screen_enabled	true	Bool
power_pin	17	UInt (GPIO)
source_pin	24	UInt (GPIO)
menu_pin	27	UInt (GPIO)
plus_pin	22	UInt (GPIO)
minus_pin	23	UInt (GPIO)

Server

On startup DashD will start a HTTP server on the specified port, which serves a basic web interface. It allows the user to change the website shown, move and resize the window, configure the lighting and press the virtual screen buttons, if those modules are enabled.

CLI Flag	Default	Unit
server_enabled	true	Bool
server_port	80	UInt (Port)

Socket

DashD will listen for UDP packets on the specified port, which can be used to control the lighting with Artemis-RGB or any compatible program that supports the Artemis Lighting Protocol. If lighting is disabled, this module will be disabled.

CLI Flag	Default	Unit
socket_enabled	true	Bool
socket_port	1872	UInt (Port)

Installation

Download the latest release from GitHub Releases for your platform. Then run the following commands in the directory where you downloaded DashD:

sudo apt-get update
sudo apt-get install chromium-browser
sudo mv DashD.* /usr/local/sbin/dashd
sudo chmod +x /usr/local/sbin/dashd

Usage

One possible way to use DashD is to run it on startup with systemd and xinit as basic display manager. To use this configuration install xinit like so:

sudo apt-get update
sudo apt-get install xserver-xorg xfonts-base xinit

Then put the following in /etc/X11/xinit/xinitrc:

#!/bin/bash

xhost +

/usr/local/sbin/dashd &> /var/log/dashd.log

Make a new systemd unit for xinit at /etc/systemd/system/xinit.service with this content:

[Unit]
Description=Xinit display manager using startx

[Service]
Type=simple
ExecStart=/usr/bin/startx -- -nocursor
Restart=always

[Install]
Alias=display-manager.service

Finally enable the service, switch to the graphical target and reboot. The logs will be put in /var/log/DashD.log.

sudo systemctl enable xinit.service
sudo systemctl set-default graphical.target
sudo reboot

Building

DashD utilizes Docker to cross-compile for the Raspberry Pi. The Dockerfile in this repository creates an image that can be used to build DashD. To build the docker image run docker build -t dashd_builder:arm32 -f Dockerfile.arm32 . in the root directory of this repository. Then run docker run --rm --volume $(pwd):/dashd/app dashd_builder:arm32 to build DashD for 32-bit. The binary is located at build/DashD.arm32. Replace arm32 with arm64 in the previous commands to build for 64-bit.

HTTP API

The endpoints ignore the HTTP method used, however POST is recommended for all, except / and /config, which should be used with GET.

Endpoint	Description	Parameters	Parameter Description
/	Get the web interface
/display	Set the website to be displayed	url	the URL of the website as a percent-encoded string data URLs are also supported
/move	Set the window position	posX posY	the x position in pixel the y position in pixel
/resize	Set the window size	width height	the width in pixel the height in pixel
/config	Get the LED count in JSON (Artemis API)
/update	Set colors of LED strip (Artemis API)	base64	a UDP packet (described below) as a base64 encoded string name is not enforced; must be the first parameter
/reset	Set all LEDs to black (Artemis API)
/power	Toggle the power button
/source	Toggle the source button
/menu	Toggle the menu button
/plus	Toggle the plus button
/minus	Toggle the minus button

UDP Lighting Protocol

Each UDP packet contains a single frame of lighting data. The first byte is the sequence number which is used for basic packet ordering and must be incremented with each request. The second byte is the channel number which is ignored by DashD because it supports only a single channel. The remaining packet consists of byte triplets which represent the RGB value in that order. The number of byte triplets does not need to be equal to the number of LEDs. Any extra bytes are ignored and LEDs not contained in the packet retain their color. To calculate the length of a packet that sets all LEDs use: 2 + (leds * 3).

License

DashD - Lightweight daemon for Raspberry Pi driven kiosks
Copyright (C) 2022 Elias*

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.