SPI API

Configuration Defines

The file spi_conf.h can be provided in the application source code, without it the default values specified in spi_master.h and spi_slave.h will be used. This file can set the following defines:

SPI master Defines

DEFAULT_SPI_CLOCK_DIV

This define sets the default clock divider, which the application can use when initialising the SPI master. See spi_clock_div parameter of spi_master_init() in Configuration Functions for clock divider format.

SPI_MASTER_MODE

The SPI mode the master operates in.

Mode

CPOL

CPHA

0

0

0

1

0

1

2

1

0

3

1

1

SPI slave Defines

SPI_SLAVE_MODE

The SPI mode the slave operates in.

Mode

CPOL

CPHA

0

0

0

1

0

1

2

1

0

3

1

1

SPI master API

Data Structures

  • spi_master_interface

    Structure containing the resources required for the SPI master interface.

    It consists of two 8bit buffered output ports, and one 8bit input port.

    Select lines are intentionally not part of API, they are simple port outputs, which depend on how many slaves there are and how they’re connected.

    Structure Members:

    • clock blk1

    • clock blk2

    • out buffered port:8 mosi

    • out buffered port:8 sclk

    • in buffered port:8 miso

Configuration Functions

  • void spi_master_init(spi_master_interface &spi_if, int spi_clock_div)

    Configure ports and clocks, clearing port buffers.

    Must be called before any SPI data input or output functions are used.

    Example: To achieve an sclk frequency of 25MHz, a divider of 2 must be specified, as 100(MHz)/(2*2) = 25(MHz).

    Example: To achieve an sclk frequency of 625kHz, a divider of 80 must be specified, as 100(MHz)/(2*80) = 0.625(MHz).

    This function has the following parameters:

    • spi_if

      Resources for the SPI interface being initialised

    • spi_clock_div

      SPI clock frequency is fref/(2*spi_clock_div), where freq defaults to 100MHz

  • void spi_master_shutdown(spi_master_interface &spi_if)

    Stops the clocks running.

    Should be called when all SPI input and output is completed.

    This function has the following parameters:

    • spi_if

      Resources for the SPI interface being shutdown

    • Receive Functions

    • unsigned char spi_master_in_byte(spi_master_interface &spi_if)

      Receive one byte.

      Most significant bit first order. Big endian byte order.

      This function has the following parameters:

      • spi_if

        Resources for the SPI interface

    This function returns:

    The received byte

  • unsigned short spi_master_in_short(spi_master_interface &spi_if)

    Receive one short.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:
    • This function returns:

    The received short

  • unsigned int spi_master_in_word(spi_master_interface &spi_if)

    Receive one word.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters: This function returns:

    The received word

  • void spi_master_in_buffer(spi_master_interface &spi_if, unsigned char buffer[], int num_bytes)

    Receive specified number of bytes.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

    • Transmit Functions

  • void spi_master_out_short(spi_master_interface &spi_if, unsigned short data)

    Transmit one short.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

  • void spi_master_out_word(spi_master_interface &spi_if, unsigned int data)

    Transmit one word.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

  • void spi_master_out_buffer(spi_master_interface &spi_if, const unsigned char buffer[], int num_bytes)

    Transmit specified number of bytes.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

    • SPI slave API

    Data Structures

    Configuration Functions

  • void spi_slave_shutdown(spi_slave_interface &spi_if)

    Stops the clocks running, and disables the ports.

    Should be called when all SPI input and output is completed.

    This function has the following parameters:

    • Receive Functions

    This function returns:

    The received byte

  • unsigned short spi_slave_in_short(spi_slave_interface &spi_if)

    Receive one short.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters: This function returns:

    The received short

  • unsigned int spi_slave_in_word(spi_slave_interface &spi_if)

    Receive one word.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters: This function returns:

    The received word

  • void spi_slave_in_buffer(spi_slave_interface &spi_if, unsigned char buffer[], int num_bytes)

    Receive specified number of bytes.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

    • Transmit Functions

  • void spi_slave_out_short(spi_slave_interface &spi_if, unsigned short data)

    Transmit one short.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

  • void spi_slave_out_word(spi_slave_interface &spi_if, unsigned int data)

    Transmit one word.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters:

  • void spi_slave_out_buffer(spi_slave_interface &spi_if, const unsigned char buffer[], int num_bytes)

    Transmit specified number of bytes.

    Most significant bit first order. Big endian byte order.

    This function has the following parameters: