19.8.4.1.3 Workflow

system_init();

configure_spi_slave();

1. Create configuration struct.

   struct spi_config config_spi_slave;
   

2. Get default configuration to edit.

   spi_get_config_defaults(&config_spi_slave);
   

3. Set the SPI in slave mode.

   config_spi_slave.mode = SPI_MODE_SLAVE;
   

4. Enable preloading of shift register.

   config_spi_slave.mode_specific.slave.preload_enable = true;
   

5. Set frame format to SPI frame.

   config_spi_slave.mode_specific.slave.frame_format = SPI_FRAME_FORMAT_SPI_FRAME;
   

6. Set MUX setting E.

   config_spi_slave.mux_setting = EXT1_SPI_SERCOM_MUX_SETTING;
   

7. Set pinmux for pad 0 (data in MOSI).

   config_spi_slave.pinmux_pad0 = EXT1_SPI_SERCOM_PINMUX_PAD0;
   

8. Set pinmux for pad 1 (slave select).

   config_spi_slave.pinmux_pad1 = EXT1_SPI_SERCOM_PINMUX_PAD1;
   

9. Set pinmux for pad 2 (data out MISO).

   config_spi_slave.pinmux_pad2 = EXT1_SPI_SERCOM_PINMUX_PAD2;
   

10. Set pinmux for pad 3 (SCK).

    config_spi_slave.pinmux_pad3 = EXT1_SPI_SERCOM_PINMUX_PAD3;
    

11. Initialize SPI module with configuration.

    spi_init(&spi_slave_instance, EXT1_SPI_MODULE, &config_spi_slave);
    

12. Enable SPI module.

    spi_enable(&spi_slave_instance);
    

configure_spi_slave_callbacks();

1. Register callback function for buffer transmitted.

   spi_register_callback(&spi_slave_instance, spi_slave_callback,
           SPI_CALLBACK_BUFFER_RECEIVED);
   

2. Enable callback for buffer transmitted.

   spi_enable_callback(&spi_slave_instance, SPI_CALLBACK_BUFFER_RECEIVED);