====== Using the HAL with the gpio subsystem ======
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/HalTest4.cpp|HalTest4.cpp]]. 

The system uses real hardware inputs and output. The hardware could be (TODO). You also need to install the necessary wrapper library, see [[getting_started:install_wrapper|]]. 

Open a shell in the build directory of your EEROS library and run  
<code>
$ ./examples/hal/halTest4 -c HalTest4ConfigGpio.json  
</code>

This examples creates a small control system with a couple of peripheral input and output blocks.
The main sequence alters the values on digital and analog outputs periodically. It also logs the digital and analog inputs.