88 lines
2.6 KiB
ReStructuredText
88 lines
2.6 KiB
ReStructuredText
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class CAN --- controller area network communication bus
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=======================================================
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CAN implements the standard CAN communications protocol. At
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the physical level it consists of 2 lines: RX and TX. Note that
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to connect the pyboard to a CAN bus you must use a CAN transceiver
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to convert the CAN logic signals from the pyboard to the correct
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voltage levels on the bus.
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Note that this driver does not yet support filter configuration
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(it defaults to a single filter that lets through all messages),
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or bus timing configuration (except for setting the prescaler).
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Example usage (works without anything connected)::
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from pyb import CAN
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can = pyb.CAN(1, pyb.CAN.LOOPBACK)
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can.send('message!', 123) # send message to id 123
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can.recv(0) # receive message on FIFO 0
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Constructors
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------------
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.. class:: pyb.CAN(bus, ...)
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Construct a CAN object on the given bus. ``bus`` can be 1-2, or 'YA' or 'YB'.
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With no additional parameters, the CAN object is created but not
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initialised (it has the settings from the last initialisation of
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the bus, if any). If extra arguments are given, the bus is initialised.
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See ``init`` for parameters of initialisation.
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The physical pins of the CAN busses are:
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- ``CAN(1)`` is on ``YA``: ``(RX, TX) = (Y3, Y4) = (PB8, PB9)``
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- ``CAN(2)`` is on ``YB``: ``(RX, TX) = (Y5, Y6) = (PB12, PB13)``
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Methods
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-------
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.. method:: can.init(mode, extframe=False, prescaler=100, \*, sjw=1, bs1=6, bs2=8)
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Initialise the CAN bus with the given parameters:
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- ``mode`` is one of: NORMAL, LOOPBACK, SILENT, SILENT_LOOPBACK
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If ``extframe`` is True then the bus uses extended identifiers in the frames (29 bits).
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Otherwise it uses standard 11 bit identifiers.
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.. method:: can.deinit()
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Turn off the CAN bus.
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.. method:: can.any(fifo)
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Return ``True`` if any message waiting on the FIFO, else ``False``.
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.. method:: can.recv(fifo, \*, timeout=5000)
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Receive data on the bus:
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- ``fifo`` is an integer, which is the FIFO to receive on
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- ``timeout`` is the timeout in milliseconds to wait for the receive.
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Return value: buffer of data bytes.
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.. method:: can.send(send, addr, \*, timeout=5000)
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Send a message on the bus:
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- ``send`` is the data to send (an integer to send, or a buffer object).
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- ``addr`` is the address to send to
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- ``timeout`` is the timeout in milliseconds to wait for the send.
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Return value: ``None``.
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Constants
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---------
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.. data:: CAN.NORMAL
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.. data:: CAN.LOOPBACK
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.. data:: CAN.SILENT
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.. data:: CAN.SILENT_LOOPBACK
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the mode of the CAN bus
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