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machine.SPI.rst

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.. currentmodule:: machine

class SPI -- a Serial Peripheral Interface bus protocol (master side)

SPI is a synchronous serial protocol that is driven by a master. At the physical level, a bus consists of 3 lines: SCK, MOSI, MISO. Multiple devices can share the same bus. Each device should have a separate, 4th signal, SS (Slave Select), to select a particular device on a bus with which communication takes place. Management of an SS signal should happen in user code (via machine.Pin class).

Constructors

Methods

.. method:: SPI.init(baudrate=1000000, \*, polarity=0, phase=0, bits=8, firstbit=SPI.MSB, sck=None, mosi=None, miso=None, pins=(SCK, MOSI, MISO))

   Initialise the SPI bus with the given parameters:

     - ``baudrate`` is the SCK clock rate.
     - ``polarity`` can be 0 or 1, and is the level the idle clock line sits at.
     - ``phase`` can be 0 or 1 to sample data on the first or second clock edge
       respectively.
     - ``bits`` is the width in bits of each transfer. Only 8 is guaranteed to be supported by all hardware.
     - ``firstbit`` can be ``SPI.MSB`` or ``SPI.LSB``.
     - ``sck``, ``mosi``, ``miso`` are pins (machine.Pin) objects to use for bus signals. For most
       hardware SPI blocks (as selected by ``id`` parameter to the constructor), pins are fixed
       and cannot be changed. In some cases, hardware blocks allow 2-3 alternative pin sets for
       a hardware SPI block. Arbitrary pin assignments are possible only for a bitbanging SPI driver
       (``id`` = -1).
     - ``pins`` - WiPy port doesn't ``sck``, ``mosi``, ``miso`` arguments, and instead allows to
       specify them as a tuple of ``pins`` parameter.


.. method:: SPI.deinit()

   Turn off the SPI bus.


.. method:: SPI.read(nbytes, write=0x00)

    Read a number of bytes specified by ``nbytes`` while continuously writing
    the single byte given by ``write``.
    Returns a ``bytes`` object with the data that was read.


.. method:: SPI.readinto(buf, write=0x00)

    Read into the buffer specified by ``buf`` while continuously writing the
    single byte given by ``write``.
    Returns ``None``.

    Note: on WiPy this function returns the number of bytes read.


.. method:: SPI.write(buf)

    Write the bytes contained in ``buf``.
    Returns ``None``.

    Note: on WiPy this function returns the number of bytes written.


.. method:: SPI.write_readinto(write_buf, read_buf)

    Write the bytes from ``write_buf`` while reading into ``read_buf``.  The
    buffers can be the same or different, but both buffers must have the
    same length.
    Returns ``None``.

    Note: on WiPy this function returns the number of bytes written.

Constants

.. data:: SPI.MASTER

   for initialising the SPI bus to master; this is only used for the WiPy


.. data:: SPI.MSB

   set the first bit to be the most significant bit


.. data:: SPI.LSB

   set the first bit to be the least significant bit