====== Hardware Abstraction Layer ======
The HAL provides an interface between the robot control system (consisting of control system, safety system, and sequencer) and the hardware of the robot. Any signal from a hardware input or output must pass through the HAL. 
  * [[eeros_architecture:hal:using_hal|]]
  * [[eeros_architecture:hal:configuration_file|]]
    * [[eeros_architecture:hal:scaling|]]
    * [[eeros_architecture:hal:scaling_multi|]]
    * [[eeros_architecture:hal:config_ros|]]
  * [[eeros_architecture:hal:feature_functions|]]
  * [[eeros_architecture:hal:hardware_libraries|]]
    * [[eeros_architecture:hal:hardware_libraries_sim|]]
  * [[eeros_architecture:hal:input_devices|]]
===== Configuration of the HAL =====
The inputs and outputs of the system are given by a specific hardware setup. This can vary widely among different systems. To account for many possible hardware settings we use a configuration file. This file describes the current hardware together with the necessary library to access them, see [[Configuration File]].
The configuration given in the file can be loaded as follows:
<code cpp>
  HAL& hal = HAL::instance();
  hal.readConfigFromFile(std::string file);
</code>

Most probably you want to pass the configuration file name via parameters to ''main'' with:
<code cpp>
  HAL& hal = HAL::instance();
  hal.readConfigFromFile(&argc, argv);
</code>
Now, you can pass the configuration file with
<code>
$ ./myApplication -c /path/to/config/NameOfConfigurationFile
</code>
Note: This HAL option has to be the first option if additional command line options are used.

This call causes the following actions:
  * the configuration file will be parsed
  * the necessary hardware libraries will be loaded
  * for each channel an appropriate object is created with the id given in the configuration file
  * these objects will be registered in the HAL manager
===== Available HAL Objects =====
All input objects of the HAL have a common type base type ''InputInterface'' while the output objects have a common type ''OutputInterface''. Digital inputs or outputs are of type ''Input<bool>'' or ''Output<bool>'' respectively. Analog inputs or outputs are of type ''ScalableInput<double>'' or ''ScalableOutput<double>'' respectively. \\
The following functions are available:
<code cpp>
  OutputInterface* getOutput(std::string name, bool exclusive = true);
  Output<bool>* getLogicOutput(std::string name, bool exclusive = true);
  ScalableOutput<double>* getScalableOutput(std::string name, bool exclusive = true);
  InputInterface* getInput(std::string name, bool exclusive = true);
  Input<bool>* getLogicInput(std::string name, bool exclusive = true);
  ScalableInput<double>* getScalableInput(std::string name, bool exclusive = true);
</code>