fsfw/doc/README-core.md

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## FSFW Core Modules
These core modules provide the most important functionalities of the
Flight Software Framework
### Clock
* This is a class of static functions that can be used at anytime
* Leap Seconds must be set if any time conversions from UTC to other times is used
### ObjectManager
* Must be created during program startup
* The component which handles all references. All SystemObjects register at this component.
* Any SystemObject needs to have a unique ObjectId. Those can be managed like objects::framework_objects.
* A reference to an object can be get by calling the following function. T must be the specific Interface you want to call.
A nullptr check of the returning Pointer must be done. This function is based on Run-time type information.
``` c++
template <typename T> T* ObjectManagerIF::get( object_id_t id )
```
* A typical way to create all objects on startup is a handing a static produce function to the ObjectManager on creation.
By calling objectManager->initialize() the produce function will be called and all SystemObjects will be initialized afterwards.
### Event Manager
* Component which allows routing of events
* Other objects can subscribe to specific events, ranges of events or all events of an object.
* Subscriptions can be done during runtime but should be done during initialization
* Amounts of allowed subscriptions can be configured in `FSFWConfig.h`
### Health Table
* A component which holds every health state
* Provides a thread safe way to access all health states without the need of message exchanges
### Stores
* The message based communication can only exchange a few bytes of information inside the message itself. Therefore, additional information can
be exchanged with Stores. With this, only the store address must be exchanged in the message.
* Internally, the FSFW uses an IPC Store to exchange data between processes. For incoming TCs a TC Store is used. For outgoing TM a TM store is used.
* All of them should use the Thread Safe Class storagemanager/PoolManager
### Tasks
There are two different types of tasks:
* The PeriodicTask just executes objects that are of type ExecutableObjectIF in the order of the insertion to the Tasks.
* FixedTimeslotTask executes a list of calls in the order of the given list. This is intended for DeviceHandlers, where polling should be in a defined order. An example can be found in defaultcfg/fsfwconfig/pollingSequence