f47f9c05aa
This adds basic API description for ADC and DAC peripherals. External ADC/DAC controllers are listed as well. Signed-off-by: Michal Lenc <michallenc@seznam.cz>
76 lines
2.3 KiB
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76 lines
2.3 KiB
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===========
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DAC Drivers
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===========
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- ``include/nuttx/analog/dac.h``. All structures and APIs needed
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to work with DAtC drivers are provided in this header file. This
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header file includes:
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#. Structures and inerface descriptions needed to develop a
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low-level, architecture-specific, DAC driver.
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#. To register the DAC driver with a common DAC character
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driver.
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#. Interfaces needed for interfacing user programs with the
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common DAC character driver.
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- ``drivers/analog/dac.c``. The implementation of the common DAC
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character driver.
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Application Programming Interface
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=================================
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The first necessary thing to be done in order to use the DAC driver from an
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application is to include the correct header filer. It contains the
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Application Programming Interface to the PWM driver. To do so, include
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.. code-block:: c
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#include <nuttx/analog/dac.h>
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DAC driver is registered as a POSIX character device driver into ``/dev``
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namespace. It is necessary to open the device to get a file descriptor for
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further operations. This can be done with standard POSIX ``open()`` call.
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Standard POSIX ``write()`` call is used to send data from an application to
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a controller. Structure ``dac_msg_s`` is used to pass the data/samples.
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.. c:struct:: dac_msg_s
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.. code-block:: c
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begin_packed_struct struct dac_msg_s
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{
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/* The 8-bit DAC Channel */
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uint8_t am_channel;
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/* DAC convert result (4 bytes) */
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int32_t am_data;
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} end_packed_struct;
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Application Example
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~~~~~~~~~~~~~~~~~~~
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An example application can be found in ``nuttx-apps`` repository under
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path ``examples/dac``. It provides command line interface to write data
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to DAC channels.s
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Configuration
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=============
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This section describes DAC driver configuration in ``Kconfig``. The reader
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should refer to target documentation for target specific configuration.
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The peripheral is enabled by ``CONFIG_ANALOG`` and ``CONFIG_DAC`` options,
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respectively. The FIFO queue size is configurable with ``CONFIG_DAC_FIFOSIZE``.
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This size is limited to ``255`` to fit into ``uint8_t``.
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External Devices
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================
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NuttX also provides support for various external DAC devices. These usually
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communicates with MCU with I2C or SPI peripherals.
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.. toctree::
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:maxdepth: 1
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:glob:
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*/*
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