class SPI – Serial Peripheral Interface
SPI is a serial protocol that is driven by a master. At the physical level there are 3 lines: SCK, MOSI, MISO.
See usage model of I2C; SPI is very similar. Main difference is parameters to init the SPI bus:
from machine import SPI
spi = SPI(0, mode=SPI.MASTER, baudrate=1000000, polarity=0, phase=0, firstbit=SPI.MSB)
Only required parameter is mode, must be
Quick Usage Example
from machine import SPI
# configure the SPI master @ 2MHz
# this uses the SPI default pins for CLK, MOSI and MISO (``P10``, ``P11`` and ``P14``)
spi = SPI(0, mode=SPI.MASTER, baudrate=2000000, polarity=0, phase=0)
spi.write(bytes([0x01, 0x02, 0x03, 0x04, 0x05])) # send 5 bytes on the bus
spi.read(5) # receive 5 bytes on the bus
rbuf = bytearray(5)
spi.write_readinto(bytes([0x01, 0x02, 0x03, 0x04, 0x05]), rbuf) # send a receive 5 bytes
Quick Usage Example using non-default pins
from machine import SPI
# configure the SPI master @ 2MHz
# this uses the SPI non-default pins for CLK, MOSI and MISO (``P19``, ``P20`` and ``P21``)
spi = SPI(0, mode=SPI.MASTER, baudrate=2000000, polarity=0, phase=0, pins=('P19','P20','P21'))
spi.write(bytes([0x01, 0x02, 0x03, 0x04, 0x05])) # send 5 bytes on the bus
spi.read(5) # receive 5 bytes on the bus
rbuf = bytearray(5)
spi.write_readinto(bytes([0x01, 0x02, 0x03, 0x04, 0x05]), rbuf) # send a receive 5 bytes
Constructors
class machine.SPI(id, ...)
Construct an SPI object on the given bus. id
can be only 0. 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.
Methods
spi.init(mode, baudrate=1000000, * , polarity=0, phase=0, bits=8, firstbit=SPI.MSB, pins=(CLK, MOSI, MISO))
Initialise the SPI bus with the given parameters:
mode
must beSPI.MASTER .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 of each transfer, accepted values are 8, 16 and 32.firstbit
can beSPI.MSB orSPI.LSB .pins
is an optional tuple with the pins to assign to the SPI bus. If the pins argument is not given the default pins will be selected (P10
as CLK,P11
as MOSI andP14
as MISO). If pins is passed as None then no pin assignment will be made.
spi.deinit()
Turn off the SPI bus.
spi.write(buf)
Write the data contained in buf
. Returns the number of bytes written.
spi.read(nbytes, * , write=0x00)
Read the nbytes
while writing the data specified by write
. Return the number of bytes read.
spi.readinto(buf, * , write=0x00)
Read into the buffer specified by buf
while writing the data specified by write
. Return the number of bytes read.
spi.write_readinto(write_buf, read_buf)
Write from write_buf
and read into read_buf
. Both buffers must have the same length. Returns the number of bytes written
Constants
For initialising the SPI bus to master
Set the first bit to be the most significant bit
Set the first bit to be the least significant bit