50 lines
1.5 KiB
ReStructuredText
50 lines
1.5 KiB
ReStructuredText
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.. _sdhc_api:
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SDHC
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####
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The SDHC api offers a generic interface for interacting with an SD host
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controller device. It is used by the SD subsystem, and is not intended to be
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directly used by the application
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Basic Operation
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***************
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SD Host Controller
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==================
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An SD host controller is a device capable of sending SD commands to an attached
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SD card. These commands can be sent using the native SD protocol, or over SPI.
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the SDHC api is designed to provide a generic way to send commands to and
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interact with attached SD devices.
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Requests
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========
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The core of the SDHC api is the :c:func:`sdhc_request` api. Requests contain a
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:c:struct:`sdhc_command` command structure, and an optional
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:c:struct:`sdhc_data` data structure. The caller may check the return code,
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or the ``response`` field of the SD command structure to determine if the
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SDHC request succeeded. The data structure allows the caller to specify a
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number of blocks to transfer, and a buffer location to read or write them from.
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Whether the provided buffer is used for sending or reading data depends on the
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command opcode provided.
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Host Controller I/O
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===================
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The :c:func:`sdhc_set_io` api allows the user to change I/O settings of the SD
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host controller, such as clock frequency, I/O voltage, and card power. Not all
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controllers will support applying all I/O settings. For example, SPI mode
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controllers typically cannot toggle power to the SD card.
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Related configuration options:
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* :kconfig:option:`CONFIG_SDHC`
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API Reference
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*************
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.. doxygengroup:: sdhc_interface
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