19.8.3.1.2 Code

A sample buffer to send via SPI.

static uint8_t wr_buffer[BUF_LENGTH] = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
         0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x10, 0x11, 0x12, 0x13
};
static uint8_t rd_buffer[BUF_LENGTH];

Number of entries in the sample buffer.

#define BUF_LENGTH 20

GPIO pin to use as Slave Select.

#define SLAVE_SELECT_PIN EXT1_PIN_SPI_SS_0

A globally available software device instance struct to store the SPI driver state while it is in use.

struct spi_module spi_master_instance;

A globally available peripheral slave software device instance struct.

struct spi_slave_inst slave;

A function for configuring the SPI.

void configure_spi_master(void)
{
    struct spi_config config_spi_master;
    struct spi_slave_inst_config slave_dev_config;
    /* Configure and initialize software device instance of peripheral slave */
    spi_slave_inst_get_config_defaults(&slave_dev_config);
    slave_dev_config.ss_pin = SLAVE_SELECT_PIN;
    spi_attach_slave(&slave, &slave_dev_config);
    /* Configure, initialize and enable SERCOM SPI module */
    spi_get_config_defaults(&config_spi_master);
    config_spi_master.mux_setting = EXT1_SPI_SERCOM_MUX_SETTING;
    /* Configure pad 0 for data in */
    config_spi_master.pinmux_pad0 = EXT1_SPI_SERCOM_PINMUX_PAD0;
    /* Configure pad 1 as unused */
    config_spi_master.pinmux_pad1 = PINMUX_UNUSED;
    /* Configure pad 2 for data out */
    config_spi_master.pinmux_pad2 = EXT1_SPI_SERCOM_PINMUX_PAD2;
    /* Configure pad 3 for SCK */
    config_spi_master.pinmux_pad3 = EXT1_SPI_SERCOM_PINMUX_PAD3;
    spi_init(&spi_master_instance, EXT1_SPI_MODULE, &config_spi_master);

    spi_enable(&spi_master_instance);

}

A function for configuring the callback functionality of the SPI.

void configure_spi_master_callbacks(void)
{
    spi_register_callback(&spi_master_instance, callback_spi_master,
            SPI_CALLBACK_BUFFER_TRANSCEIVED);
    spi_enable_callback(&spi_master_instance, SPI_CALLBACK_BUFFER_TRANSCEIVED);
}

A global variable that can flag to the application that the buffer has been transferred.

volatile bool transrev_complete_spi_master = false;

Callback function.

static void callback_spi_master( struct spi_module *const module)
{
    transrev_complete_spi_master = true;
}

Add to user application main().

/* Initialize system */
system_init();

configure_spi_master();
configure_spi_master_callbacks();