.. 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).