86 lines
2.6 KiB
ReStructuredText
86 lines
2.6 KiB
ReStructuredText
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.. _machine.SPI:
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class SPI -- a master-driven serial protocol
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============================================
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SPI is a serial protocol that is driven by a master. At the physical level
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there are 3 lines: SCK, MOSI, MISO.
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.. only:: port_wipy
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See usage model of I2C; SPI is very similar. Main difference is
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parameters to init the SPI bus::
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from machine import SPI
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spi = SPI(0, mode=SPI.MASTER, baudrate=1000000, polarity=0, phase=0, firstbit=SPI.MSB)
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Only required parameter is mode, must be SPI.MASTER. Polarity can be 0 or
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1, and is the level the idle clock line sits at. Phase can be 0 or 1 to
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sample data on the first or second clock edge respectively.
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Constructors
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------------
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.. only:: port_wipy
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.. class:: machine.SPI(id, ...)
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Construct an SPI object on the given bus. ``id`` can be only 0.
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With no additional parameters, the SPI 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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Methods
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-------
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.. method:: spi.init(mode, baudrate=1000000, \*, polarity=0, phase=0, bits=8, firstbit=SPI.MSB, pins=(CLK, MOSI, MISO))
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Initialise the SPI bus with the given parameters:
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- ``mode`` must be ``SPI.MASTER``.
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- ``baudrate`` is the SCK clock rate.
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- ``polarity`` can be 0 or 1, and is the level the idle clock line sits at.
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- ``phase`` can be 0 or 1 to sample data on the first or second clock edge
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respectively.
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- ``bits`` is the width of each transfer, accepted values are 8, 16 and 32.
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- ``firstbit`` can be ``SPI.MSB`` only.
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- ``pins`` is an optional tupple with the pins to assign to the SPI bus.
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.. method:: spi.deinit()
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Turn off the SPI bus.
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.. method:: spi.write(buf)
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Write the data contained in ``buf``.
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Returns the number of bytes written.
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.. method:: spi.read(nbytes, *, write=0x00)
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Read the ``nbytes`` while writing the data specified by ``write``.
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Return the number of bytes read.
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.. method:: spi.readinto(buf, *, write=0x00)
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Read into the buffer specified by ``buf`` while writing the data specified by
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``write``.
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Return the number of bytes read.
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.. method:: spi.write_readinto(write_buf, read_buf)
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Write from ``write_buf`` and read into ``read_buf``. Both buffers must have the
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same length.
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Returns the number of bytes written
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Constants
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---------
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.. data:: SPI.MASTER
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for initialising the SPI bus to master
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.. data:: SPI.MSB
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set the first bit to be the most significant bit
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