Skip to content

Latest commit

 

History

History
106 lines (68 loc) · 2.6 KB

mruby_io_SPI_en.md

File metadata and controls

106 lines (68 loc) · 2.6 KB
Raw

SPI

  • A class that supports SPI bus.
  • This specification defines only master devices and transfers in 8-bit units.
  • The Chip Select (CS/SS) will be managed using GPIO functionality and is not defined within the SPI class.

Constructor

SPI.new( id=nil, *params )

  • Generates an SPI object by specifying the physical unit indicated by "id."
  • "id" can be omitted when there is only one physical unit.

Optional Parameters

param type description
unit --- Specification of the SPI unit
frequency Integer Frequency (default 1MHz)
mode Integer 0 to 3 (default 0)
first_bit Constant SPI::MSB_FIRST or SPI::LSB_FIRST (default MSB_FIRST)

Example of use:

# Generate an SPI object with the default settings.
spi = SPI.new()

# Use sn SPI device of unit 1 with a frequency of 10MHz.
spi = SPI.new( unit:1, frequency:10_000_000 )

mode parameter

mode CPOL CPHA Idle state clock polarity Sampling timing
0 0 0 Low Rising edge mode0
1 0 1 Low Falling edge mode1
2 1 0 High Falling edge mode2
3 1 1 High Rising edge mode3

Device-specific

  • Not all parameters may be supported.

Instance Methods

setmode( *params )

  • Changes the operating mode (parameters) of the SPI.
  • The parameters are specified according to the constructor.

Example of use:

spi.setmode( mode:3 )

read( read_bytes ) -> String

  • Reads data of read_bytes bytes from the SPI bus.
  • At the same time, data will be output as 0.

Example of use:

data = spi.read( 32 )

write( *outputs ) -> nil

  • Outputs data specified in outputs to the SPI bus.
  • outputs can be specified as an Integer, Array, or String.

Example of use:

spi.write( 0x30, 0xa2 )
spi.write( "\x30\xa2" )
i2c.write( 0x02, 0xee, 0xad, 0x00, data_string )  # useful for EEPROM

transfer( outputs, additional_read_bytes = 0 ) -> String

  • Outputs data specified in outputs to the SPI bus while simultaneously reading data (General-purpose transfer).
  • outputs can be specified as an Integer, Array, or String.
  • If additional_read_bytes is specified, it will output 0x00 after the outputs.

Example of use:

s = spi.transfer( 0b0000_0101, 1 )  # s will return a 2-byte String