67 lines
2.6 KiB
ReStructuredText
67 lines
2.6 KiB
ReStructuredText
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========================
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SocketCAN Device Drivers
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========================
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- **``include/nuttx/net/netdev.h``**. All structures and APIs
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needed to work with drivers are provided in this header file.
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The structure struct net_driver_s defines the interface and is
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passed to the network via netdev_register().
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- **``include/nuttx/can.h``**. CAN & CAN FD frame data
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structures.
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- **``int netdev_register(FAR struct net_driver_s *dev, enum net_lltype_e lltype)'``**.
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Each driver registers itself by calling netdev_register().
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- **``Include/nuttx/net/can.h``**. contains lookup tables for CAN
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dlc to CAN FD len sizes named
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.. code-block:: c
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extern const uint8_t can_dlc_to_len[16];
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extern const uint8_t len_to_can_dlc[65];
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- **Initialization sequence is as follows**.
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#. up_netinitialize(void) is called on startup of NuttX in this
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function you call your own init function to initialize your
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CAN driver
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#. In your own init function you create the net_driver_s
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structure set required init values and register the required
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callbacks for SocketCAN
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#. Then you ensure that the CAN interface is in down mode
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(usually done by calling the d_ifdown function)
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#. Register the net_driver_s using netdev_register
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- **Receive sequence is as follows**.
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#. Device generates interrupt
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#. Process this interrupt in your interrupt handler
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#. When a new CAN frame has been received you process this
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frame
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#. When the CAN frame is a normal CAN frame you allocate the
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can_frame struct, when it's a CAN FD frame you allocate a
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canfd_frame struct (note you can of course preallocate and
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just use the pointer).
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#. Copy the frame from the driver to the struct you've
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allocated in the previous step.
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#. Point the net_driver_s d_buf pointer to the allocated
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can_frame
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#. Call the ``can_input(FAR struct net_driver_s *dev)``
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function ``include/nuttx/net/can.h``
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- **Transmit sequence is as follows**.
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#. Socket layer executes d_txavail callback
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#. An example of the txavail function can be found in
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``arch/arm/src/s32k1xx/s32k1xx_flexcan.c``
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#. An example of the txpoll function can be found in
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``arch/arm/src/s32k1xx/s32k1xx_flexcan.c``
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#. In your ``transmit(struct driver_s *priv)`` function you
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check the length of ``net_driver_s.d_len`` whether it
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matches the size of a ``struct can_frame`` or
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``struct canfd_frame`` then you cast the content of the
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``net_driver_s.d_buf`` pointer to the correct CAN frame
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struct
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