fsfw/doc/README-core.md

## 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. 

```cpp
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` folder