36 lines
1.6 KiB
ReStructuredText
36 lines
1.6 KiB
ReStructuredText
==========================
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IO Expander Device Drivers
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==========================
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- ``include/nuttx/ioexpander/ioexpander.h`` and ``include/nuttx/ioexpander/gpio.h``.
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All structures and APIs needed to work with ioexpander drivers are provided in
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this header file.
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- ``struct ioexpander_ops_s``. Each ioexpand device driver must implement
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an instance of ``struct ioexpander_ops_s``. That structure defines a
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call table with the methods, and we also provide macros to help access methods.
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- we also provide method ``gpio_lower_half`` to make ioexpander compatible with normal gpio.
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- **Binding ioexpander Drivers**. ioexpander drivers are not normally directly
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accessed by user code, we should always get lower level drivers, for example I2C,
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and map extended gpio feature same asa normal gpio. See for example,
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``int nrf52_sx1509_initialize(void)``
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in ``boards/arm/nrf52/thingy52/src/nrf52_sx1509.c``. In general, the binding
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sequence is:
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#. Get an instance of ``struct i2c_master_s`` from the
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hardware-specific I2C device driver, and
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#. Provide that instance and configurations to the ioexpander initialization method
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to get the ``struct ioexpander_dev_s`` ioe device instance.
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#. Then use ioe device instance to do ioexpander operations, or use ``gpio_lower_half``
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to make ioexpand compatible with normal gpio.
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- **Examples**: ``drivers/ioexpander/pca9555.c``,
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``drivers/input/aw86225.c``,
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``drivers/analog/lmp92001.c``,
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``drivers/ioexpander/ioe_rpmsg.c``,
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``boards/sim/sim/sim/src/sim_ioexpander.c``,
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``boards/arm/nrf52/thingy52/src/nrf52_sx1509.c`` etc.
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