kopia lustrzana https://github.com/micropython/micropython
111 wiersze
3.5 KiB
ReStructuredText
111 wiersze
3.5 KiB
ReStructuredText
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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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 pyb import SPI
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spi = SPI(1, SPI.MASTER, baudrate=600000, polarity=1, phase=0, crc=0x7)
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Only required parameter is mode, SPI.MASTER or SPI.SLAVE. Polarity can be
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0 or 1, and is the level the idle clock line sits at. Phase can be 0 or 1
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to sample data on the first or second clock edge respectively. Crc can be
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None for no CRC, or a polynomial specifier.
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Additional method for SPI::
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data = spi.send_recv(b'1234') # send 4 bytes and receive 4 bytes
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buf = bytearray(4)
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spi.send_recv(b'1234', buf) # send 4 bytes and receive 4 into buf
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spi.send_recv(buf, buf) # send/recv 4 bytes from/to buf
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Constructors
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------------
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.. class:: pyb.SPI(bus, ...)
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Construct an SPI object on the given bus. ``bus`` can be 1 or 2.
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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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The physical pins of the SPI busses are:
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- ``SPI(1)`` is on the X position: ``(NSS, SCK, MISO, MOSI) = (X5, X6, X7, X8) = (PA4, PA5, PA6, PA7)``
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- ``SPI(2)`` is on the Y position: ``(NSS, SCK, MISO, MOSI) = (Y5, Y6, Y7, Y8) = (PB12, PB13, PB14, PB15)``
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At the moment, the NSS pin is not used by the SPI driver and is free
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for other use.
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Methods
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-------
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.. method:: spi.deinit()
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Turn off the SPI bus.
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.. method:: spi.init(mode, baudrate=328125, \*, polarity=1, phase=0, bits=8, firstbit=SPI.MSB, ti=False, crc=None)
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Initialise the SPI bus with the given parameters:
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- ``mode`` must be either ``SPI.MASTER`` or ``SPI.SLAVE``.
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- ``baudrate`` is the SCK clock rate (only sensible for a master).
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.. method:: spi.recv(recv, \*, timeout=5000)
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Receive data on the bus:
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- ``recv`` can be an integer, which is the number of bytes to receive,
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or a mutable buffer, which will be filled with received bytes.
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- ``timeout`` is the timeout in milliseconds to wait for the receive.
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Return value: if ``recv`` is an integer then a new buffer of the bytes received,
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otherwise the same buffer that was passed in to ``recv``.
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.. method:: spi.send(send, \*, timeout=5000)
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Send data 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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- ``timeout`` is the timeout in milliseconds to wait for the send.
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Return value: ``None``.
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.. method:: spi.send_recv(send, recv=None, \*, timeout=5000)
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Send and receive data on the bus at the same time:
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- ``send`` is the data to send (an integer to send, or a buffer object).
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- ``recv`` is a mutable buffer which will be filled with received bytes.
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It can be the same as ``send``, or omitted. If omitted, a new buffer will
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be created.
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- ``timeout`` is the timeout in milliseconds to wait for the receive.
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Return value: the buffer with the received bytes.
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Constants
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---------
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.. data:: LSB
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set the first bit to LSB
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.. data:: MASTER
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for initialising the bus to master mode
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.. data:: MSB
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set the first bit to MSB
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.. data:: SLAVE
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for initialising the bus to slave mode
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