3 title: Architecture presentation
5 https://git.automotivelinux.org/apps/agl-service-signal-composer/plain/docs/part-1/1-Architecture.md?h=master
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14 Here is a quick picture about the signaling architecture :
18 Key here are on both layers, **low** and **high**.
20 - **Low levels** binding used as _AGL service_, handle data exchange protocol to
21 decode/encode and retransmit with an AGL compatible format using **Application
22 Framework** events. These are divided into two parts, which are :
23 - A transport Layer binding's plug-in that is able to read/write from a device.
24 - Decoding/Encoding parts that expose signals.
25 - **High level signal composer** binding gathers multiple **low level** signaling
26 sources. Then from these sources, it exposes theirs **raw** signals or more interesting
27 can creates new virtuals signals from them. Example:
28 A signal made from gps latitude and longitude that computes the heading of
29 vehicle. This is modular and each signal source should be handled by specific
30 plugins which take care of get the underlying event from **low level** or
31 define signaling composition with simple or complex operation to output value
34 A transport plug-in is a shared library that shares a common API to be
35 compatible with **low level** services that is:
37 - **open/close**: method to open a handle which could be a socket, file or
39 - **read/write**: method to read and write a stream of data.
41 Configuration is made by sending a special packet using a write method to the
42 handle. In brief, this could be compared to the layer 1 and 2 of [OSI model].
44 There are three main parts with **Signal Composer**:
46 - Configuration files which could be splitted in differents files. That will
48 - metadata with name of **signal composer** api name
49 - additionnals configurations files
50 - plugins used if so, **low level** signals sources
57 Here is a little terminology guide to set the vocabulary:
59 - **api**: a binding API name
60 - **action**: a function called at a certain time
61 - **callbacks**: a function called at a certain time
62 - **event**: the raw event that materialize the signal
63 - **plugins**: a C/C++ code with functions that be called by signal composer
65 - **sources**: an external binding API that generate signals for the signal
67 - **signals**: an event generated by the **Application Framework**
68 - **virtual signals**: a signal composed of **raw signals** with value
69 calculated by a **callbacks**
70 - **raw signals**: an event generated by a **low level** binding
72 [OSI model]: https://en.wikipedia.org/wiki/OSI_model
73 [GlobalArchitecture]: pictures/Global_Signaling_Architecture.png "Global architecture"