DMA UART1 TX

[ssudhir]

Hi,

As we mentioned earlier, we are using LPC4357. We have connected an embedded ethernet module to UART1. We are planning to use DMA for both RX and TX. To transmit a packet via DMA we have called

Chip_GPDMA_Transfer function.  We are using ethernet to communicate with a socket based server application. The server App is receiving whatever is in that uartABStart – buffer.

Sample code

dmaChannelNumTx = Chip_GPDMA_GetFreeChannel(LPC_GPDMA, _GPDMA_CONN_UART_Tx);

Chip_GPDMA_Transfer(LPC_GPDMA, dmaChannelNumTx,

                                                                                  (uint32_t) &uartABStart[0],

                                                                                  _GPDMA_CONN_UART_Tx,

                                                                                  GPDMA_TRANSFERTYPE_M2P_CONTROLLER_DMA,

                                                                                  sizeof(uartABStart));

Now the question is, Do we need to call  Chip_GPDMA_Transfer function Whenever we want to send a packet via DMA?  Since that function call sets up that channel , is there different method to trigger DMA by giving the source address and  size?

Thanks

[xiangjun_rong]

Hi,

I think calling the Chip_GPDMA_Transfer() function is required when you want to send characters via DMA, calling the function will start the uart transfer.

Hope it can help you

BR

XiangJun Rong

[ssudhir]

Thanks for the response.

Do we need to get a free channel for each transfer or only once?

Thanks

On Wed, Jun 26, 2019 at 5:44 AM xiangjun.rong <admin@community.nxp.com>

[xiangjun_rong]

Hi,

I do not think you need call the

dmaChannelNumTx = Chip_GPDMA_GetFreeChannel(LPC_GPDMA, _GPDMA_CONN_UART_Tx);

for each transfer, it is okay to call the function only once.

BR

XiangJun Rong