topic Re: DMA UART1 TX in LPC Microcontrollers

DMA UART1 TX

ssudhir — Tue, 25 Jun 2019 19:47:39 GMT

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

Re: DMA UART1 TX

xiangjun_rong — Wed, 26 Jun 2019 09:44:00 GMT

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

XiangJun Rong

Re: DMA UART1 TX

ssudhir — Wed, 26 Jun 2019 12:27:13 GMT

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>

Re: DMA UART1 TX

xiangjun_rong — Fri, 28 Jun 2019 09:15:09 GMT

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.

XiangJun Rong