9dc7640ede
The generic SPI GPIO chip select support now respects devicetree flags for signal active level. Update all cs-gpios properties to specify active low. Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
56 lines
1.7 KiB
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56 lines
1.7 KiB
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.. _sdhc_api:
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SDHC
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####
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Zephyr includes support for connecting an SD card via the SPI bus.
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This can be used with Zephyr's built-in filesystem support to read and
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write FAT formatted cards. Both standard and high-capacity SD cards are
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supported.
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The system has been tested with cards from Samsung, SanDisk, and 4V
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with sizes from 2 GiB to 32 GiB in single partition mode. Higher
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capacity cards should also work but haven't been tested. Please let
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us know if they work!
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MMC cards are not supported and will be ignored.
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.. note:: The system does not support inserting or removing cards while the
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system is running. The cards must be present at boot and must not be
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removed. This may be fixed in future releases.
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FAT filesystems are not power safe so the filesystem may become
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corrupted if power is lost or if the card is removed.
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Enabling
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********
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For example, this devicetree fragment adds an SDHC card slot on ``spi1``,
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uses ``PA27`` for chip select, and runs the SPI bus at 24 MHz once the
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SDHC card has been initialized:
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.. code-block:: none
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&spi1 {
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status = "okay";
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cs-gpios = <&porta 27 GPIO_ACTIVE_LOW>;
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sdhc0: sdhc@0 {
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compatible = "zephyr,mmc-spi-slot";
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reg = <0>;
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status = "okay";
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label = "SDHC0";
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spi-max-frequency = <24000000>;
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};
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};
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Usage
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*****
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The SDHC card will be automatically detected and initialized by the
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filesystem driver when the board boots.
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To read and write files and directories, see the :ref:`file_system_api` in
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:zephyr_file:`include/fs.h` such as :c:func:`fs_open()`,
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:c:func:`fs_read()`, and :c:func:`fs_write()`.
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