19.8.2.1.3 Workflow

  1. Initialize system. 
    system_init();
  2. Set-up the SPI. 
    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);