Chapter 15: Digging into the IIO Framework

Industrial input/output (IIO) is a kernel subsystem dedicated to analog-to-digital converters (ADCs) and digital-to-analog converters (DACs). With the growing numbers of sensors (measurement devices with analog-to-digital or digital-to-analog capabilities) with different code implementations, scattered across kernel sources, gathering them became necessary. That is what the IIO framework does, in a generic way. Jonathan Cameron and the Linux IIO community have been developing it since 2009. Accelerometers, gyroscopes, current/voltage measurement chips, light sensors, and pressure sensors all fall into the IIO family of devices.

The IIO model is based on device and channel architecture:

• The device represents the chip itself, the top level of the hierarchy.
• The channel represents a single acquisition line of the device. A device may have one or more channels. For example, an accelerometer is a device with three channels, one for...