SAML21走起27:SERCOM 串口DMA方式

<P> </P>

<P>#include <asf.h>

struct usart_module usart_instance;

struct dma_resource usart_dma_resource_rx;

struct dma_resource usart_dma_resource_tx;</P>

<P>#define BUFFER_LEN    8

static uint16_t string[BUFFER_LEN];

COMPILER_ALIGNED(16)

DmacDescriptor example_descriptor_rx;

DmacDescriptor example_descriptor_tx;</P>

<P>

static void transfer_done_rx(struct dma_resource* const resource )

{    dma_start_transfer_job(&usart_dma_resource_tx);}

static void transfer_done_tx(struct dma_resource* const resource )

{    dma_start_transfer_job(&usart_dma_resource_rx);}

static void configure_dma_resource_rx(struct dma_resource *resource)

{    

 struct dma_resource_config config;

 dma_get_config_defaults(&config);

 config.peripheral_trigger = EDBG_CDC_SERCOM_DMAC_ID_RX;

 config.trigger_action = DMA_TRIGGER_ACTON_BEAT;

 dma_allocate(resource, &config);}

static void setup_transfer_descriptor_rx(DmacDescriptor *descriptor)

{    struct dma_descriptor_config descriptor_config;

  dma_descriptor_get_config_defaults(&descriptor_config);

  descriptor_config.beat_size = DMA_BEAT_SIZE_HWORD;

  descriptor_config.src_increment_enable = false;

  descriptor_config.block_transfer_count = BUFFER_LEN;

  descriptor_config.destination_address =            (uint32_t)string + sizeof(string);

  descriptor_config.source_address =            (uint32_t)(&usart_instance.hw->USART.DATA.reg);

  dma_descriptor_create(descriptor, &descriptor_config);}

static void configure_dma_resource_tx(struct dma_resource *resource)

{    struct dma_resource_config config;

  dma_get_config_defaults(&config);

  config.peripheral_trigger = EDBG_CDC_SERCOM_DMAC_ID_TX;

  config.trigger_action = DMA_TRIGGER_ACTON_BEAT;

  dma_allocate(resource, &config);}

static void setup_transfer_descriptor_tx(DmacDescriptor *descriptor)

{    struct dma_descriptor_config descriptor_config;

  dma_descriptor_get_config_defaults(&descriptor_config);

  descriptor_config.beat_size = DMA_BEAT_SIZE_HWORD;

  descriptor_config.dst_increment_enable = false;

  descriptor_config.block_transfer_count = BUFFER_LEN;

  descriptor_config.source_address = (uint32_t)string + sizeof(string);

  descriptor_config.destination_address =        (uint32_t)(&usart_instance.hw->USART.DATA.reg);

  dma_descriptor_create(descriptor, &descriptor_config);}

static void configure_usart(void)

{    struct usart_config config_usart;

  usart_get_config_defaults(&config_usart);

  config_usart.baudrate    = 9600;

  config_usart.mux_setting = EDBG_CDC_SERCOM_MUX_SETTING;

  config_usart.pinmux_pad0 = EDBG_CDC_SERCOM_PINMUX_PAD0;

  config_usart.pinmux_pad1 = EDBG_CDC_SERCOM_PINMUX_PAD1;

  config_usart.pinmux_pad2 = EDBG_CDC_SERCOM_PINMUX_PAD2;

  config_usart.pinmux_pad3 = EDBG_CDC_SERCOM_PINMUX_PAD3;

  while (usart_init(&usart_instance,            EDBG_CDC_MODULE, &config_usart) != STATUS_OK) {    }

       usart_enable(&usart_instance);}

  

int main (void)

{

 

   

   /* Initialize the system and console*/

   system_init();

     configure_usart();

  configure_dma_resource_rx(&usart_dma_resource_rx);

  configure_dma_resource_tx(&usart_dma_resource_tx);

  setup_transfer_descriptor_rx(&example_descriptor_rx);

  setup_transfer_descriptor_tx(&example_descriptor_tx);

  dma_add_descriptor(&usart_dma_resource_rx, &example_descriptor_rx);

  dma_add_descriptor(&usart_dma_resource_tx, &example_descriptor_tx);

  dma_register_callback(&usart_dma_resource_rx, transfer_done_rx,            DMA_CALLBACK_TRANSFER_DONE);

  dma_register_callback(&usart_dma_resource_tx, transfer_done_tx,            DMA_CALLBACK_TRANSFER_DONE);

  dma_enable_callback(&usart_dma_resource_rx,            DMA_CALLBACK_TRANSFER_DONE); 

  dma_enable_callback(&usart_dma_resource_tx,            DMA_CALLBACK_TRANSFER_DONE);

  

   dma_start_transfer_job(&usart_dma_resource_rx);    while (true) {    }</P>

<P>}

</P>