2.30.12 DMAC_LinkedListDescriptorSetup Function

C 

void DMAC_LinkedListDescriptorSetup (dmac_descriptor_registers_t* currentDescriptor,
DMAC_CHANNEL_CONFIG setting,
const void *srcAddr,
const void *destAddr,
size_t blockSize,
dmac_descriptor_registers_t* nextDescriptor);

Summary

Sets up linked list descriptor

Description

This function sets up DMA linked list descriptor. Once the descriptor is setup, DMAC_ChannelLinkedListTransfer API can be used to initiate the linked list mode of DMA transfer.

Precondition

  • DMAC should have been initialized by calling the DMAC_Initialize.

  • The Linked List option should have been enabled in MCC DMA manager

Parameters

ParamDescription
currentDescriptorAddress of current descriptor
settingBlock transfer setting of current descriptor
srcAddrSource address of the DMAC transfer
destAddrDestination address of the DMAC transfer. If the CRC engine is enabled and configured in Memory mode then store the seed to be used by CRC engine in the destination address.
blockSizeSize of the transfer block in bytes.
nextDescriptorAddress of next descriptor. if user wants to stop the transfer, this argument should be NULL.

Returns

None.

Example 

uint8_t txPingBuffer[] = "INITIAL_DMA_DATA_FROM_PING_BUFFER";
uint8_t txPongBuffer[] = "initial_dma_data_from_pong_buffer";

__attribute__((__aligned__(16))) static dmac_descriptor_registers_t pTxLinkedListDesc[2];

#define BUFEER0_TX_BTCTRL (DMAC_BTCTRL_STEPSIZE_X1 | DMAC_BTCTRL_SRCINC_Msk | \
DMAC_BTCTRL_BEATSIZE_BYTE | DMAC_BTCTRL_BLOCKACT_INT | DMAC_BTCTRL_VALID_Msk)

// Setup DMA linked list
DMAC_LinkedListDescriptorSetup (&pTxLinkedListDesc[0],
BUFEER0_TX_BTCTRL,
(void *)&txPingBuffer[0],
(void *)&SERCOM1_REGS->SPIM.SERCOM_DATA,
sizeof(txPingBuffer),
&pTxLinkedListDesc[1]);
DMAC_LinkedListDescriptorSetup (&pTxLinkedListDesc[1],
BUFEER0_TX_BTCTRL,
(void *)&txPongBuffer[0],
(void *)&SERCOM1_REGS->SPIM.SERCOM_DATA,
sizeof(txPongBuffer),
// this setting will enable continuous transfer, to stop the transfer this argument should be NULL.
&pTxLinkedListDesc[0]);

// Start the DMA in linked list mode
DMAC_ChannelLinkedListTransfer(DMAC_CHANNEL_1, &pTxLinkedListDesc[0]);

Remarks

None.