hsuantinglu / idf

Input Device Framework

IDF is a software library that provides an infrastructure for interfacing software with physical input devices. Examples of common devices include hand controllers, joysticks, foot pedals, computer mice, game controllers, etc. Conceptually, the framework can be extended to support any device that produces digital output. IDF additionally presents, and is itself an implementation of, a design methodology that encourages application developers to program against domain-specific interfaces rather than particular hardware devices. This abstraction frees the application from the details of communicating with the underlying devices, resulting in robust and flexible code that is device-agnostic. IDF ensures that devices meet application interface requirements, supports many-to-many relationships between application interfaces and devices, allows for flexible and dynamic interpretation of device inputs, and provides methods for transforming and combining inputs.

The Problem

Software often requires input from external physical devices. The range of devices, data formats, and mediums of communication are virtually limitless. There thus exists a need for a method by which to deliver data to applications in a consistent, well-defined manner, and in an application-defined format. The vast array of ways that devices output data necessitates a separation between the application, which is concerned only with what the data represents, and the devices themselves, which have no notion of how their data is to be used. There must then be a way to bridge this disconnect without burdening either side with details of the other. Barring such a tool, applications may be written against specific devices, but this pollutes the program's primary functionality with a secondary task and forces the application interface to conform to the device's output format. As the consumer of the data, it is preferable for the application to define its own context-specific interface through which the data is received. Changes in the device, data format, or communication medium should not alter the application interface.

A Solution

IDF serves to completely separate the "business" logic of a program from the logic responsible for reading raw input from physical devices. Beyond simply isolating the code, it further aims to abstract each side from the other, so that both pieces can be developed fully independently. Its goal is to enable application developers to write robust, flexible code with clearly delineated interface points which are defined in a domain and context most meaningful to the application.

Architecture

Simulation Interface Layer

This layer defines the point at which external inputs enter the application's primary functional logic. It is here that a developer decides what kind of inputs his system will accept, and in what format it will accept them. Once this interface is established, the developer encodes it as a "controller" by extending IDF and specializing it for this particular application. Devices that wish to service this interface must meet this controller's contract. This layer is the only one with which the primary functional logic should interact.

Hardware Interface Layer

This layer represents the physical input devices and is responsible for all aspects of communication with the hardware, primarily reading and decoding raw data. Devices are classified by their communication medium, and a representation exists for each specific device supported.

Input Abstraction Layer

This layer provides a means by which to tie the above two layers together. It represents device input layouts without regard to their particular medium of communication. A device's available data, represented in this layer, is populated by the Hardware Interface Layer as it is received from the physical device. This data can then be presented to a controller from the Simulation Interface Layer, provided that it can be made to meet that controller's contract.

Wiki

See the wiki for installation instructions and lots of additional information.

License

IDF is released under the NASA Open Source Agreement, Version 1.3.