UART Transmission with DMA on MSP432

Emru

Hi!

I want to send data over UART with using the DMA Controller. Directly sending data over "UART_transmitData(EUSCI_A0_MODULE,sendData)" is working. Now I configured the DMA, but it doesn't work. I hope you can help me.

My global variables in a struct globalVar

uint8_t sendBufferUart[8];
uint8_t controlTable[1024];

Here is the code for configuration the dma:

    //DMA configuration
    DMA_enableModule();

    DMA_setControlBase(ptrGlobalVar->controlTable);

    DMA_assignChannel(DMA_CH0_EUSCIA0TX);

    DMA_disableChannelAttribute(DMA_CH0_EUSCIA0TX, UDMA_ATTR_ALTSELECT | UDMA_ATTR_USEBURST | UDMA_ATTR_HIGH_PRIORITY | UDMA_ATTR_REQMASK);

    DMA_setChannelControl(UDMA_PRI_SELECT | DMA_CH0_EUSCIA0TX, UDMA_SIZE_8 | UDMA_SRC_INC_8 | UDMA_DST_INC_NONE | UDMA_ARB_1);

    DMA_setChannelTransfer(UDMA_PRI_SELECT | DMA_CH0_EUSCIA0TX, UDMA_MODE_BASIC, ptrGlobalVar->sendBufferUart ,(void*) UART_getTransmitBufferAddressForDMA(EUSCI_A0_MODULE), 8);

    DMA_assignInterrupt(DMA_INT0,0);

Here is the code for Change buffer and sending code:

	uint16_t time4MsStamp = globalVar.FourMsCounter + globalVar.OneSecCounter*250;


	//dma controller for sending data with less cpu using
	uint8_t *ptrBufferBeginning;
	ptrBufferBeginning = globalVar.sendBufferUart;

	ptrBufferBeginning[0] = 0xF0;	//first start byte
	ptrBufferBeginning[1] = 0x0F;   //second start byte
	ptrBufferBeginning[2] = time4MsStamp;
	ptrBufferBeginning[3] = time4MsStamp >> 8;
	ptrBufferBeginning[4] = globalVar.curADCresult;
	ptrBufferBeginning[5] = globalVar.curADCresult >>8;
	ptrBufferBeginning[6] = 0x00;
	ptrBufferBeginning[7] = 0xFF;

	DMA_enableChannel(DMA_CHANNEL_0);
	DMA_requestChannel(DMA_CHANNEL_0);

Best regards,

Emru

over 9 years ago

0 Ryan Brown1 over 9 years ago

TI__Guru**** 217857 points

Hi Emru,

DMA_INT0 is the logical OR of all completion events whereas DMA_INT1/2/3 can be mapped to the DMA completion event of any of the eight channels, therefore please use one of these instead. I do not see the line Interrupt_enableInterrupt(INT_DMA_INT1); or Interrupt_enableMaster(); which are required as well for using the DMA interrupt. You shouldn't have to request the channel either, this should happen automatically given the start of a UART transfer. Some MSP432 DMA UART examples can be found in the following threads:

e2e.ti.com/.../453931
e2e.ti.com/.../425881

Regards,
Ryan

0 Emru over 9 years ago in reply to Ryan Brown1

Prodigy 200 points

Hello Ryan,

Thank you for your answer. The Interrupts are enabled in another part of the code. Interrupts like Timer and ADC are working. How can I give the Start of an UART Transfer?

Regards,
Emru

0 Ryan Brown1 over 9 years ago in reply to Emru

TI__Guru**** 217857 points

Hello Emru,

Try manually setting the EUSCIA0 UART transmit interrupt flag. You still need to use DMA_INT1 and follow the example code provided.

Regards,
Ryan

0 Koyo Kegasa over 8 years ago

Expert 1260 points

I tried UART without interrupt.

(1) without DMA

void UART_send_text( char ascii[], int n )
{
int i;
for( i=0 ; i<n ; i++ )
{
if( ascii[i] == 0 ) return;
while (!(UCA0IFG&UCTXIFG)); // USCI_A0 TX buffer ready?
UCA0TXBUF = ascii[i];
}
}

(2) with DMA
void UART_send_text_dma( char ascii[], int n )
{
/* Assign DMA channel 0 to EUSCI_A0_TX0 */
MAP_DMA_assignChannel(DMA_CH0_EUSCIA0TX);

/* Setup the TX transfer characteristics & buffers */
MAP_DMA_setChannelControl(DMA_CH0_EUSCIA0TX | UDMA_PRI_SELECT,
UDMA_SIZE_8 | UDMA_SRC_INC_8 | UDMA_DST_INC_NONE | UDMA_ARB_1);
MAP_DMA_setChannelTransfer(DMA_CH0_EUSCIA0TX | UDMA_PRI_SELECT,
UDMA_MODE_BASIC, ascii,
(void *) MAP_SPI_getTransmitBufferAddressForDMA(EUSCI_A0_BASE),
n);

MAP_DMA_enableChannel(0);
}

(3) main
/* initialize */

char ascii_data[] = "abcdefghijklmnop"; // ascii buffer
UART_send_text( &ascii_data[0], 14 );
UART_send_text_dma( &ascii_data[0], 14 );
Both worked all right!

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UART Transmission with DMA on MSP432