SPI

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Utility

This library provides SPI communications, enabling communications with two or more microcontrollers, with the GR-COTTON board as the master device. To use this library, specify #include <SPI.h>.

SPISettings

Description

Each SPI device can be configured once as an SPISettings object.

Syntax

SPISettings mySettting(speed, dataOrder, datamode)

Parameters

speed: The speed of the communication
dataOrder: MSBFIRST or LSBFIRST
dataMode: SPI_MODE0, SPI_MODE1, SPI_MODE2, or SPI_MODE3

Returns

None

begin

Description

Initializes the SPI bus by setting SCK, MOSI and SS to outputs, pulling SCK and MOSI low, and SS high.

Syntax

SPI.begin()

Parameters

None

Returns

None

end

Description

Disables the SPI bus, and returns the pin to a general I/O port.

Syntax

SPI.end()

Parameters

None

Returns

None

beginTransaction()

Description

Initializes the SPI bus using the defined SPISettings.

Syntax

SPI.beginTransaction(mySettings)

Parameters

mySettings: The chosen settings according to SPISettings

Returns

None

endTransaction()

Description

Stop using the SPI bus. Normally, this is called after de-asserting the chip select, to allow other libraries to use the SPI bus.

Syntax

SPI.endTransaction()

Parameters

None

Returns

None

setBitOrder

Description

Sets the order of the bits shifted out of and into the SPI bus.

Syntax

SPI.setBitOrder(bitOrder)

Parameters

bitOrder: Bit order, either LSBFIRST or MSBFIRST. Default is MSBFIRST

Returns

None

setClockDivider

Description

Sets the SPI clock divider relative to the system clock.

Syntax

SPI.setClockDivider(divider)

Parameters

divider: Set one of the following:
  SPI_CLOCK_DIV2: 8MHz
  SPI_CLOCK_DIV4: 4MHz
  SPI_CLOCK_DIV8: 2MHz
  SPI_CLOCK_DIV16: 1MHz
  SPI_CLOCK_DIV32: 500kHz
  SPI_CLOCK_DIV64: 250kHz
  SPI_CLOCK_DIV128: 125kHz

Returns

None

setDataMode

Description

Sets the SPI data mode: That is, clock polarity and phase.

Syntax

SPI.setDataMode(mode)

Parameters

mode: Set one of the following. Default is Mode 0. SDMMC is not available in Modes 2 and 3.
  SPI_MODE0: Clock is low during idling, samples data at rising edge
  SPI_MODE1: Clock is low during idling, samples data at falling edge
  SPI_MODE2: Clock is high during idling, samples data at rising edge
  SPI_MODE3: Clock is high during idling, samples data at falling edge

Returns

None

transfer

Description

Transfers one byte over the SPI bus, both sending and receiving.

Syntax

SPI.transfer(value)

Parameters

value: A byte of data

Returns

The byte read from the bus.

        #include <Arduino.h>
        #include <SPI.h>
        void setup(){
            SPI.begin();
        }
            
        void loop(){
            //write
            SPI.transfer(0x55);
                
            //read
            uint8_t data = SPI.transfer(0xff);
        }