37 lines
1.6 KiB
ReStructuredText
37 lines
1.6 KiB
ReStructuredText
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===========
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CAN Drivers
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===========
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NuttX supports only a very low-level CAN driver. This driver
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supports only the data exchange and does not include any
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high-level CAN protocol. The NuttX CAN driver is split into two
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parts:
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#. An "upper half", generic driver that provides the common CAN
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interface to application level code, and
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#. A "lower half", platform-specific driver that implements the
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low-level timer controls to implement the CAN functionality.
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Files supporting CAN can be found in the following locations:
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- **Interface Definition**. The header file for the NuttX CAN
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driver resides at ``include/nuttx/can/can.h``. This header file
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includes both the application level interface to the CAN driver
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as well as the interface between the "upper half" and "lower
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half" drivers. The CAN module uses a standard character driver
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framework.
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- **"Upper Half" Driver**. The generic, "upper half" CAN driver
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resides at ``drivers/can.c``.
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- **"Lower Half" Drivers**. Platform-specific CAN drivers reside
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in ``arch/``\ *<architecture>*\ ``/src/``\ *<hardware>*
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directory for the specific processor *<architecture>* and for
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the specific *<chip>* CAN peripheral devices.
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**Usage Note**: When reading from the CAN driver multiple messages
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may be returned, depending on (1) the size the returned can
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messages, and (2) the size of the buffer provided to receive CAN
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messages. *Never assume that a single message will be returned*...
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if you do this, *you will lose CAN data* under conditions where
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your read buffer can hold more than one small message. Below is an
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example about how you should think of the CAN read operation:
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