Display Library for Linux based Single Board Computers

Table of contents

• Overview
• Installation
• Testing
• Documentation
  • Supported devices
  • API documentation
  • Fonts
• Software
  • File-system
  • Error Codes
  • Tool chain
  • Configuration
• Notes
  • Older versions

Overview

• Project Name: Display_Lib_RPI
• Author: Gavin Lyons.
• Description:

0. A C++ Library to connect electronic displays to linux based single board computers.
1. Dynamic install-able Linux C++ library.
2. 16 fonts included, new fonts can easily be added by user
3. Common graphics + print class included
4. Dependency: lgpio C Library, Provides SPI,I2C, and GPIO control.
5. Mutiple displays supported, see supported-devices, new components can be added.
6. Tested and developed on Raspberry Pis see tool chain for more details.
7. Cppcheck Status:
8. Donations welcome:

Installation

1. Download & Install the dependency lgpio C Library, if not installed. lgpio is a C library for Linux Single Board Computers(SBC) which allows control of the General Purpose Input Output pins. Install the lgpio, Installation instructions here

cd ~/Downloads
wget http://abyz.me.uk/lg/lg.zip
unzip lg.zip
cd lg
make
sudo make install

2. Download the Display_Lib_RPI library Open a Terminal in a folder where you want to download,build & test library Run following command to download latest release from github.

curl -sL https://github.com/gavinlyonsrepo/Display_Lib_RPI/archive/2.7.0.tar.gz | tar xz

3. Install library : Run 'make' and 'sudo make install' to run the makefile to build and then install library. It will be installed to usr/local/lib and usr/local/include by default.

cd Display_Lib_RPI-2.7.0
make
sudo make install

Testing

1. Next step is to test your display and installed library with the included test example files, connect up display.
2. Enter the example folder.
3. Edit the makefile in that folder to select the desired example file path for your Display. Simply edit "SRC" variable at top of the makefile. In the "User SRC directory Option Section" at top of file. Pick an example "SRC" directory path and One ONLY.
4. Run 'make' commmand. This builds the examples file using the just installed library, and creates a test executable file in "Bin".
5. Run 'make run' to run that built executable file.
6. User should now see the test routine in that file running on the display.

cd examples
# Edit the makefile in examples folder by picking the "SRC" file path you want to run
make
make run

Documentation

Supported devices

API Documentation

The application programming interface html documentation is at link hosted on github pages and generated by Doxygen. Detailed project overview images are available there.

Fonts

The font system readme for the graphic displays is in the 'doc' folder at link.

Software

File system

There are 2 makefiles.

1. Root directory makefile, builds and installs library at a system level.
2. Example directory makefile, builds a chosen example file using installed library to an executable. which can then be run. A user editable list of file paths to examples can be found in makefile.

Run 'make help' on these makefiles to see a menu of all options.(uninstall library for example)

Library naming :

1. library name = librpidisplaygl
2. Linker flags for complier = -lrpidisplaygl (also needs -llgpio for lgpio library)
3. Library File suffix = RDL
4. Project name = Display_Lib_RPI
5. Installed size = ~700 KiB.
6. Namespaces see API.documentation.

Project class overview :

Error Codes

Most functions that return a value, return a enum 'rdlib::Return_Codes'. Zero for success and a positive number for an error code. The error codes are listed in is in the 'doc' folder at link.

Tool chain

Development Tool chain:

1. Raspberry PI 5 & Raspberry PI 3 model b
2. C++ 23, g++ (Debian 14.2.0-19) 14.2.0
3. Raspbian , Debian 12 bookworm OS, 64 bit , Debian 13 Trixie OS, 64 bit.
4. lgpio library Version Number :: 131584
5. Also tested on a raspberry pi 4 see issue number 2 on github.

Configuration

A configuration file can be created which is read into program by running "rdlib_config::loadConfig()" at start of program If the file is missing it will create it at "/($HOME)/.config/rdlib_config/config.cfg". In this file logging and debug modes can be enabled they are OFF by default. A path to log file can also be set. Certain functions produce debug information to console if the debug setting is enabled. Some errors conditions trigger logging if the logging setting is enabled. The logging function can also be used in user applications: see file examples/misc_test/utilities_test/main.cpp.

Config file :

Log file example output :

Notes

Older versions

A previous version of Display_lib_RPI (V1.3.0) which used the bcm2835 library as a low level interface is in releases and can still be downloaded and used. Version 1.3.0 will NOT work on raspberry pi 5 and uses direct register access. It will only work on raspberry pi < 5.