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# Configuration

Configuration defines all in **Signal composer** each signals and sources has to be defined in it.
At start, configuration will be searched in default binding configuration directory which should be
_/var/lib/afm/applications/signal-composer/1.0/etc/_. Binding search for a file name as _init-daemon*.json_. Others files could be used to split sections and don't have 1 big fat definitions file.

Saying that you have 4 sections to define:

- **metadata**: Main parts and the only one that can't be in a separates configuration. This must appears in the main configuration file.
- **plugins** (optionnal): Declare plugins that will be used by *sources* and *signals* for the subscription and composition.
- **sources**: Declare **low level** signals sources (eg. low-can, gps, mraa, ...).
- **signals**: Declare signals, virtuals and raw.

## Metadata

Here we define some metadata about **signal composer** binding. Fields to configure
are :

- **label**: self-explanatory
- **version** (optionnal): self-explanatory
- **api**: name that the binding will be initialized to and later be accessible by **Application Framework**
- **info** (optionnal): self-explanatory
- **require** (optionnal): list of required external apis.
- **files** (optionnal): list of additionnals files. **ONLY NAME** or part of it without extension. These
 files are loaded to find sections: *plugins*, *sources* and *signals*.

## Plugins

This section is the only which is optionnal, it is needed if you develop specifics C/C++ plugins
to be used with signal-composer. LUA and API consumption does not need plugins.

Default path to search for a plugin is in the binding library directory in a subdirectory _plugins_
_/var/lib/afm/applications/signal-composer/1.0/lib/plugins_. Else you could use the environment variable _CONTROL_PLUGIN_PATH_ with a semicolon separated list of
directory.

Fields are:

- **label**: Define the plugin name. This is that label that will be used on **sources** and
 **signals** callbacks.
- **version** (optionnal): self-explanatory
- **info** (optionnal): self-explanatory
- **basename**: shared library file name **without** the extension.

## Sources

A source is a **low level** API that will be consume by the **signal composer**
to be able to expose those signals with additionnals treatments, filtering,
thinning,... and create new virtuals signals composed with basic raw signals.

A source is defined with following fields:

- **api**: Name of the source API.
- **info** (optionnal): self-explanatory
- **init** (optionnal): an **action** to take to initialize a source. May you
 have  to call a verb from that API, of create a files etc.
- **getSignals** (optionnal); an **action** to take to get signals from that
 source. These callback will be used for each signals defined later in the **signals** section. Dedicated arguments for each signal could be defined in
 **signals**.

## Signals

A signal definition could be either a **raw** one or a **virtual** one. A
 **virtual signal** is a set of existing **raw signals** associated to an
 **action** on reception which will compute the value of the signal.

- **id**: Unique identifier used inside **signal composer**, used to compose
 virtual signals.
- **event**: specify a **raw signal** coming from **low level** sources.
 Couldn't be used with **depends** field, only one of them is possible.
- **depends**: specify others signals **id** that compose it (eg: heading is
 composed with longitude+latitude signals.). Couldn't be used with **event**
 field at same time.
- **unit** (optionnal): Unit used to exprime the signal
- **frequency** (optionnal): Frequency maximum at which the signal could be
 requested or sent. This is a thinning made at **high level** so not best
 suited for performance. Used **low level** native filtering capabilities when
 possible.
- **getSignalsArgs**: a JSON object used at subscription time. Meant to enabled
 filtering capabilities at subscription and to be able to customize in general
 a subcription request by signal if needed.
- **onReceived**: an **action** to take when this signal is received!