from machine import SPI, Pin
spi = SPI(0, baudrate=400000) # Create SPI peripheral 0 at frequency of 400kHz.
# Depending on the use case, extra parameters may be required
# to select the bus characteristics and/or pins to use.
cs = Pin(4, mode=Pin.OUT, value=1) # Create chip-select on pin 4.
try:
cs(0) # Select peripheral.
spi.write(b"12345678") # Write 8 bytes, and don't care about received data.
finally:
cs(1) # Deselect peripheral.
try:
cs(0) # Select peripheral.
rxdata = spi.read(8, 0x42) # Read 8 bytes while writing 0x42 for each byte.
finally:
cs(1) # Deselect peripheral.
rxdata = bytearray(8)
try:
cs(0) # Select peripheral.
spi.readinto(rxdata, 0x42) # Read 8 bytes inplace while writing 0x42 for each byte.
finally:
cs(1) # Deselect peripheral.
txdata = b"12345678"
rxdata = bytearray(len(txdata))
try:
cs(0) # Select peripheral.
spi.write_readinto(txdata, rxdata) # Simultaneously write and read bytes.
finally:
cs(1) # Deselect peripheral.
Constructors
class machine.SPI(id, ...)
Construct an SPI object on the given bus, id. Values of id depend
on a particular port and its hardware. Values 0, 1, etc. are commonly used
to select hardware SPI block #0, #1, etc.
With no additional parameters, the SPI object is created but not
initialised (it has the settings from the last initialisation of
the bus, if any). If extra arguments are given, the bus is initialised.
See init for parameters of initialisation.
class machine.SoftSPI(baudrate=500000, *, polarity=0, phase=0, bits=8, firstbit=MSB, sck=None, mosi=None, miso=None)
Construct a new software SPI object. Additional parameters must be
given, usually at least sck, mosi and miso, and these are used
to initialise the bus. See SPI.init for a description of the parameters.
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.
In the case of hardware SPI the actual clock frequency may be lower than the
requested baudrate. This is dependent on the platform hardware. The actual
rate may be determined by printing the SPI object.
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.
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.
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.
Last updated on 24 Aug 2023.
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