Elrond Common Library (working in progress)

Open source framework for remotely controlled models, focusing on modularization and easy configuration with a declarative syntax.

The Elrond Common Library is the core of the Elrond Project. The ECL provides an API and an abstraction layer for Elrond Modules that work on differents platforms without code modifications.

Modularization

An application based on Elrond will be constitued by module instances. Every instance must work in a single task, like blinking a simple LED, or even transferring data between the peers using a complex network protocol. Instances do not interact with each other directly, and can be one of following base types:

• elrond::module::BaseGeneric: Generic type to general proposes. Does not impose rules be used, or methods to be implemented;
• elrond::module::BaseGpioModule: Specifies the implementation of the GPIO abstraction layer, therefore, every platform must have its own implementation of this class if the other modules are to have access to the GPIO header;
• elrond::module::BaseInputDriverModule: Base to implement a input driver, responsible for read input data from a periferal, like a joystick;
• elrond::module::BaseTransportModule: This base must be used to implement a transport module that abstracts for a network protocol, that during runtime, will be used by a channel manager to transmit and receive data;

The ECL provides some internal modules, see internal modules section.

Channels based model (working in progress)

Like typical electronic radio controllers, the communication between the Elrond-based peers is mapped into channels. A channel is basically a control signal that performs an action in another peer. The main advantage of Elrond is that the data link must be at least half-duplex, and can technically handle a lot more channels, and can be flexible because of software processing. Another advantage is that it is not limited by radio technologies – basically, it can be implemented on any half-duplex or full-duplex digital data stream tecnology.

The channels are managed by a channel manager, and they can be of the transmitter type (tx channel) or receiver type (rx channel). The data sent by a transmitter channel will be received by an equivalent receiver channel in another peer. A channel can be triggered by or listened to many module instances, and a module instance can trigger or listen to many channels. An application can have many channel managers, each one with its own transport module.

Compatibility

The Elrond Common Library is currently compatible with these platforms:

• Linux computers and based boards (eg. Raspberry Pi);
• MacOS computers;
• Windows computers;

Project structure

Directories and subprojects

• common: Header Only Library with code base to be shared with runtime applications and external modules, contains only interfaces and platform independent code
• platform_std: Header Only Library of standard platform code base to be shared with runtime applications and external modules, contains definitions and platform specific code to be compatible with any platform based on C++ standard libraries
• common_runtime: Library with platform independent code to be used only on runtime applications
• platform_std_runtime: Library with standard platform specific code to be used only on runtime applications
• mock: Library containing code and classes to mock test senarios to modules development
• test: Test project to validation

CMake exports

• Elrond::elrond: Interface library (Header Only Library) with base classes and code
• Elrond::elrond_runtime: Interface library (headers and defines) with runtime application base classes and code
• Elrond::elrond_runtime_src: Interface library (source code files) with runtime application base classes and code
• Elrond::mock: Static library with mocking classes for development and tests
• Elrond::catch2 Static library with a custom Catch2 unit testing framework

Use the generated file build/elrond.cmake to import the targets.

Internal modules

The Elrond Common Library includes some general proposes modules.

The pattern of parameter list is: <name>[<type>, <default>]: <description>.
If <default> is missing, the parameter value is required.

elrond::HelloWorld

This module is a simple example module that just prints a message and the life cycle hooks. The module parameters are:

• message [string, "Hello world"]: Message string that will be printed on loop method;

elrond::AnalogLed

This module maps a receiver channel to a PWM pin output. The module parameters are:

• channel [int]: number of receiver channel for input data;
• pin [int]: number of PWM pin to output;
• inverted [bool, false]: inverts the data signal. Eg. HIGH to LOW value and vice versa;
• chm [int, 0]: number of receiver channel manager;

elrond::DigitalLed

This module maps a receiver channel to a digital pin output. The module parameters are:

• channel [int]: number of receiver channel for input data;
• pin [int]: number of digital pin to output;
• inverted [bool, false]: inverts the data signal. Eg. HIGH to LOW value and vice versa;
• chm [int, 0]: number of receiver channel manager;

elrond::Servo

This module maps a receiver channel to a PWM pin output setted in servo mode. The module parameters are:

• channel [int]: number of receiver channel for input data;
• pin [int]: number of servo pin to output;
• inverted [bool, false]: inverts the data signal. Eg. HIGH to LOW value and vice versa;
• chm [int, 0]: number of receiver channel manager;

elrond::InputToChannel

This module maps an input key from an Input Driver Module to a transmitter channel. The module parameters are:

• channel [int]: number of transmitter channel for output data;
• input [int]: number of input key from Input Driver Module for input data;
• inverted [bool, false]: inverts the data signal. Eg. HIGH to LOW value and vice versa;
• chm [int, 0]: number of transmitter channel manager;
• ins [int, 0]: number of Input Driver Module;

elrond::ChannelToChannel

This module maps a receiver channel to a transmitter channel. The module parameters are:

• txCh [int]: number of transmitter channel for output data;
• txChm [int]: number of transmitter channel manager;
• rxCh [int]: number of receiver channel for output data;
• rxChm [int]: number of receiver channel manager;
• inverted [bool, false]: inverts the data signal. Eg. HIGH to LOW value and vice versa;

elrond::Loopback

This is a simple transport module, that sends the data back to the local channel manager as received data. No parameters required.