Real-Time Robotics Framework

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====== Using the HAL with the Simulator ======
The [[eeros_architecture:hal:start|]] provides an interface between the robot control system and the hardware of the robot. As we do not have any real output we will use a simulator, see [[getting_started:install_wrapper#simulator|Simulator]]. The system in this example uses inputs and outputs. 

In the EEROS library you will find a directory with examples. For this example see [[https://github.com/eeros-project/eeros-framework/blob/master/examples/hal/HalTest1.cpp|HalTest1.cpp]]. 

Open a shell in the build directory of your EEROS library and run 
<code>
$ ./halTest1 -c HalTest1Config.json
</code>
This examples creates a small control system with a couple of peripheral input and output blocks as shown below.
 [{{ :getting_started:tutorials:haltest1.png?300 | //Control system of the test program// }}]
The dashed lines denote the feedback of the signals by the simulator. \\ 
The main sequence alters the values on digital and analog outputs periodically. A separate periodic task logs the digital and analog inputs.
  * The state on the digital output 0 is reflected by the simultor to the digital input 0. The control system connects this input to the digital output 1, which in turn is reflected by the simulator to digital input 1. However, the second reflection is ''inverted'' and we get the logical inversion of digital output 0. The value of digital input 0 changes every 5 seconds.
  * A constant value is output to analog output 0 and 2. These values change every 10 seconds. Both are reflected onto analog inputs 0 and 2, respectively.

===== Accessing Output Signals Directly =====
A peripheral output block delivers a signal to external hardware. Its signal value can be accessed with a get method, see line 41 in the comment in the example code in [[https://github.com/eeros-project/eeros-framework/blob/master/examples/hal/HalTest1.cpp|HalTest1.cpp]].

Alternatively the signal in the HAL could be accessed by getting an reference to the corresponding output block with
<code cpp>
auto digOut = hal.getLogicOutput("dOut0", false);  // line 37
</code>
The signal value can then be logged with
block with
<code cpp>
log.info() << digOut->get(); // line 42
</code>
You have to make sure to access the output with non-exclusive rights, because the control system already has a handle to it, see line 25 in ''halTest1.hpp''. Likewise, the control system must access the same output in the same fashion.