Configure the DMA

  1. Create a DMA resource configuration structure, which can be filled out to adjust the configuration of a single DMA transfer. 
    struct dma_resource_config config;
  2. Initialize the DMA resource configuration struct with the module's default values. 
    dma_get_config_defaults(&config);
    Note: This should always be performed before using the configuration struct to ensure that all values are initialized to known default settings.
  3. Set extra configurations for the DMA resource. ADC_DMAC_ID_RESRDY trigger causes a beat transfer in this example. 
    #if (SAMC21)
    config.peripheral_trigger = ADC1_DMAC_ID_RESRDY;
#else
    config.peripheral_trigger = ADC_DMAC_ID_RESRDY;
#endif
    config.trigger_action = DMA_TRIGGER_ACTON_BEAT;
  4. Allocate a DMA resource with the configurations. 
    dma_allocate(resource, &config);
  5. Create a DMA transfer descriptor configuration structure, which can be filled out to adjust the configuration of a single DMA transfer. 
    struct dma_descriptor_config descriptor_config;
  6. Initialize the DMA transfer descriptor configuration struct with the module's default values. 
    dma_descriptor_get_config_defaults(&descriptor_config);
    Note: This should always be performed before using the configuration struct to ensure that all values are initialized to known default settings.
  7. Set the specific parameters for a DMA transfer with transfer size, source address, and destination address. 
    descriptor_config.beat_size = DMA_BEAT_SIZE_HWORD;
descriptor_config.dst_increment_enable = false;
descriptor_config.src_increment_enable = false;
descriptor_config.block_transfer_count = 1000;
descriptor_config.source_address = (uint32_t)(&adc_instance.hw->RESULT.reg);
#if (SAML21)
    descriptor_config.destination_address = (uint32_t)(&dac_instance.hw->DATA[DAC_CHANNEL_0].reg);
#else
    descriptor_config.destination_address = (uint32_t)(&dac_instance.hw->DATA.reg);
#endif
    descriptor_config.next_descriptor_address = (uint32_t)descriptor;
  8. Create the DMA transfer descriptor. 
    dma_descriptor_create(descriptor, &descriptor_config);
  9. Add DMA descriptor to DMA resource. 
    dma_add_descriptor(&example_resource, &example_descriptor);