Inter-Integrated Circuit (I2C) Bus
Overview
Note
The terminology used in Zephyr I2C APIs follows that of the NXP I2C Bus Specification Rev 7.0. These changed from previous revisions as of its release October 1, 2021.
I2C (Inter-Integrated Circuit, pronounced “eye squared see”) is a commonly-used two-signal shared peripheral interface bus. Many system-on-chip solutions provide controllers that communicate on an I2C bus. Devices on the bus can operate in two roles: as a “controller” that initiates transactions and controls the clock, or as a “target” that responds to transaction commands. A I2C controller on a given SoC will generally support the controller role, and some will also support the target mode. Zephyr has API for both roles.
I2C Controller API
Zephyr’s I2C controller API is used when an I2C peripheral controls the bus, particularly the start and stop conditions and the clock. This is the most common mode, used to interact with I2C devices like sensors and serial memory.
This API is supported in all in-tree I2C peripheral drivers and is considered stable.
I2C Target API
Zephyr’s I2C target API is used when an I2C peripheral responds to transactions initiated by a different controller on the bus. It might be used for a Zephyr application with transducer roles that are controlled by another device such as a host processor.
This API is supported in very few in-tree I2C peripheral drivers. The API is considered experimental, as it is not compatible with the capabilities of all I2C peripherals supported in controller mode.
Configuration Options
Related configuration options: