LED Panel

 

LED Panel Release status: beta [box doku]
Description	Displays a ticker on the LED Panel in the space
Author(s)	Matthias

The LED Panel actually consists 2 32x128 LED matrixes with a HUB75 connected to a Raspberry Pi 1. The panels are provided by Jorgen, the pi by Matthias The custom software can retrieve messages via MQTT (what else) and display them in two rows. The first row is the "larger" one, the second row the smaller one. The content and format of the text can be heavily customized via MQTT (see below).

Software

• Based on the RPI-RGB-LED-Matrix project from hzeller [1].
• Uses the C++ MQTT Paho library (needs to be compiled and installed to /usr/local/lib & /usr/local/include accordingly)
• The Code is located here https://github.com/siedi/rpi-led-mqtt
• The LED software is automatically launched on startup via the crontab of the pi user and running in the background.

Run it

The program needs to run as root to access the gpios. Without any parameters, it will start with the defaults configured in the source code.

 sudo ./led-mqtt

The following command line parameters are available:

parameter	description
-S <xxx>	Set MQTT server

MQTT topics & commands

The topic structure is <prefix>/<command>/<parameter>, e.g. mumalab/room/ledpanel/set/once1

• prefix: as give by the command line
• command: "set" to set a value. There are currently no other commands implemented (like get)
• parameter: see table below
• payload: the value to set

topic parameter	description	value example
text1	Sets the text of the ticker in the first, upper line.	Welcome to the MuMaLab!
text2	Sets the text of the ticker in the second, lower line.	We love LEDs!
once1	Interrupts the current ticker in the first line and displays this ticker once. Afterward displays the old text1 ticker.	ALARM!!!
once2	Interrupts the current ticker in the second line and displays this ticker once. Afterward displays the old text2 ticker.	Let's go!
color1	The RGB value of the first line, as a string, comma separated.	255,0,128
color2	The RGB value of the second line, as a string, comma separated.	255,0,128
font1	Name of the font file as on the server for the first text line.	9x18.bdf
font2	Name of the font file as on the server for the second text line.	5x8.bdf

Software Compilation

In case you need to setup a new system and compile the software again, here are some hints.

You might need to install the one or the other Debian package (e.g. build-essential libssl-dev libjsoncpp-dev). You will find out when the compilation fails :-).

• Install the PAO libraries:

 # Install the c client first
 git clone http://git.eclipse.org/gitroot/paho/org.eclipse.paho.mqtt.c.git
 cd org.eclipse.paho.mqtt.c
 make
 make install
 cd ..
 git clone http://git.eclipse.org/gitroot/paho/org.eclipse.paho.mqtt.cpp.git
 cd org.eclipse.paho.mqtt.cpp

There is a bug (or feature?) in the C++ library: The MQTT authorization with username and password is in the C++ library not implemented (in C it is). There is a patch around which adds it: https://bugs.eclipse.org/bugs/show_bug.cgi?id=480007 Apply it before proceeding.

 make
 sudo cp -av lib/* /usr/local/lib/
 sudo cp -r src/mqtt /usr/local/include/

• Install led-mqtt:

 git clone -recursive https://github.com/siedi/rpi-led-mqtt.git
 cd rpi-led-mqtt
 make