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.. _smbus_api:
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2023-03-28 22:10:21 +08:00
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System Management Bus (SMBus)
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#############################
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.. contents::
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:local:
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:depth: 2
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Overview
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********
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System Management Bus (SMBus) is derived from I2C for communication
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with devices on the motherboard. A system may use SMBus to communicate
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with the peripherals on the motherboard without using dedicated control
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lines. SMBus peripherals can provide various manufacturer information,
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report errors, accept control parameters, etc.
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Devices on the bus can operate in three roles: as a Controller that
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initiates transactions and controls the clock, a Peripheral that
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responds to transaction commands, or a Host, which is a specialized
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Controller, that provides the main interface to the system's CPU.
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Zephyr has API for the Controller role.
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SMBus peripheral devices can initiate communication with Controller
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with two methods:
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* **Host Notify protocol**: Peripheral device that supports the Host Notify
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protocol behaves as a Controller to perform the notification. It writes
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a three-bytes message to a special address "SMBus Host (0x08)" with own
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address and two bytes of relevant data.
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* **SMBALERT# signal**: Peripheral device uses special signal SMBALERT# to
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request attention from the Controller. The Controller needs to read one byte
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from the special "SMBus Alert Response Address (ARA) (0x0c)". The peripheral
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device responds with a data byte containing its own address.
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Currently, the API is based on `SMBus Specification`_ version 2.0
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.. note::
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See :ref:`coding_guideline_inclusive_language` for information about
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the terminology used in this API.
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.. _smbus-controller-api:
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SMBus Controller API
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********************
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Zephyr's SMBus controller API is used when an SMBus device controls the bus,
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particularly the start and stop conditions and the clock. This is
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the most common mode used to interact with SMBus peripherals.
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Configuration Options
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*********************
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Related configuration options:
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* :kconfig:option:`CONFIG_SMBUS`
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API Reference
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*************
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.. doxygengroup:: smbus_interface
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.. _SMBus Specification: http://smbus.org/specs/smbus20.pdf
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