Elma

Elma is an event loop and process manager for embedded and reactive systems. Elma is structured as a C++ library of classes on top of which you build your own C++ project. It keeps track of processes, finite state machines, events, and communication channels, executing them at specified frequencies. Elma was developed as part of the University of Washington's ECE P 520 course on advanced embedded systems programming. More information on how Elma was designed can be found in the links below:

• Event loop management
• Events and finite state machines
• HTTP in event loops

Installation

The source code for Elma is on Github.

From Dockerhub

To get started, you will need a C++ build environment. We have provided one with the Docker container elma, which you can use as follows:

git clone https://github.com/klavinslab/elma.git
cd elma
docker run -v $PWD:/source -it klavins/elma:latest bash
make
examples/bin/basic

From the Dockerfile

You can also build the docker environment, described in env/Dockerfile, yourself, with the following commands:

git clone https://github.com/klavinslab/elma.git
cd elma
docker build -t myelma .
docker run -v $PWD:/source -it myelma bash
make
examples/bin/basic

Manual Installation

To install Elma without using Docker, you will need to install the following tools:

• gcc 4.9 or an equivalent C/C++ compiler that supports at least C++14
• Make (if you want to use the makefile. Alternatively, you can use some other build manager)
• Doxygen
• Google Test
• Neils Lohmann's JSON library: https://github.com/nlohmann/json
• My fork of yhirose's HTTP library

Installation on Unix systems (e.g. Raspbian)

First install required packages available through apt-get

sudo apt-get update
sudo apt-get install -y cmake
sudo apt-get install -y cppcheck
sudo apt-get install -y graphviz
sudo apt-get install -y doxygen
sudo apt-get install -y cmake
sudo apt-get install -y libssl-dev

Next, install Google Test

cd /usr/src
sudo git clone https://github.com/google/googletest.git
cd googletest
sudo mkdir install
cd install
sudo cmake ../
sudo make
sudo make install

Next, install the json library

sudo mkdir /usr/local/include/json
cd /usr/local/include/json
sudo curl -O -J -L https://github.com/nlohmann/json/releases/download/v3.5.0/json.hpp
sudo mv json.hpp json.h

Next, install httplib

cd /tmp
git clone https://github.com/klavins/cpp-httplib.git
sudo mkdir /usr/local/include/httplib
sudo mv /tmp/cpp-httplib/httplib.h /usr/local/include/httplib

Now you should be ready to install elma:

cd ~
mkdir Code
cd Code
git clone https://github.com/klavinslab/elma.git
cd elma
make

Note that the Makefile should detect if you are on a pi by using the command

uname -m

which on a pi 3 model B+ returns 'armv71'. If your pi is different, you might need to change the ifeq statments in test/Makefile and examples/Makefile.

If you would like to treat elma as a library, so you can link in other code, you should link to the relevant files in to the unversal system resources (usr) as follows:

ln -s include /usr/local/include/elma
ln -s lib/libelma.a /usr/local/lib/libelma.a

Then you can do

#include "elma/elma.h"

in your code and use the -lelma flag while linking. See the example elma project for an example.

Usage

See the examples in the examples directory for how to build new event loops with Elma.

License

This software is open source and uses the MIT license. Details can be found here.