| .. include:: <isonum.txt> | 
 |  | 
 | ============ | 
 | Introduction | 
 | ============ | 
 |  | 
 | The main purpose of the Industrial I/O subsystem (IIO) is to provide support | 
 | for devices that in some sense perform either | 
 | analog-to-digital conversion (ADC) or digital-to-analog conversion (DAC) | 
 | or both. The aim is to fill the gap between the somewhat similar hwmon and | 
 | :doc:`input <../input>` subsystems. Hwmon is directed at low sample rate | 
 | sensors used to monitor and control the system itself, like fan speed control | 
 | or temperature measurement. :doc:`Input <../input>` is, as its name suggests, | 
 | focused on human interaction input devices (keyboard, mouse, touchscreen). | 
 | In some cases there is considerable overlap between these and IIO. | 
 |  | 
 | Devices that fall into this category include: | 
 |  | 
 | * analog to digital converters (ADCs) | 
 | * accelerometers | 
 | * capacitance to digital converters (CDCs) | 
 | * digital to analog converters (DACs) | 
 | * gyroscopes | 
 | * inertial measurement units (IMUs) | 
 | * color and light sensors | 
 | * magnetometers | 
 | * pressure sensors | 
 | * proximity sensors | 
 | * temperature sensors | 
 |  | 
 | Usually these sensors are connected via :doc:`SPI <../spi>` or | 
 | :doc:`I2C <../i2c>`. A common use case of the sensors devices is to have | 
 | combined functionality (e.g. light plus proximity sensor). |