Supporting gist for circular DMA operation

circular-interrupt.c

// enable circular mode
DMA1_Channel4->CCR |= DMA_CCR_CIRC;

// enable interrpt after full transfer
DMA1_Channel4->CCR |= DMA_CCR_TCIE;

cmar.c

const char * msg = "Hello world\r\n\0";	

// set memory address to address of string
DMA1_Channel4->CMAR = (uint32_t)msg;

counter.c

// set number od dma transactions
DMA1_Channel4->CNDTR = 13;

cpar.c

// USART TX is mapped to DMA1 channel 4
// set peripheral address to USART data register
DMA1_Channel4->CPAR = (uint32_t)&USART1->DR;

dma-circular.cpp

// empty

dmat.c

// Enable DMA mode for transmitter
USART1->CR3 |= USART_CR3_DMAT;

enable_dma_channel.c

DMA1_Channel4->CCR |= DMA_CCR_EN;

main.c

int main(void)
{
	dma1_clock_enable();
	usart1_init();
	dma_usart_tx_init();
	dma_usart_tx_enable();
	usart1_enable();
	while (1);
}

priority.c

// set priprity to lowest value
DMA1_Channel4->CCR &= ~(DMA_CCR_PL_0 | DMA_CCR_PL_1);

transaction-properties.c

// set data transfer direction - memory -> peripheral
DMA1_Channel4->CCR |= DMA_CCR_DIR;

// set memory address size to 8 bits (Address is incremented by this much)
DMA1_Channel4->CCR &= ~(DMA_CCR_MSIZE_0 | DMA_CCR_MSIZE_0);

// set peripheral size to 8 bits (Has no effect as this is not incremented)
DMA1_Channel4->CCR &= ~(DMA_CCR_PSIZE_0 | DMA_CCR_PSIZE_0);

// set memory address incement by 1byte
DMA1_Channel4->CCR |= DMA_CCR_MINC;

// disable increment mode on peripheral address
DMA1_Channel4->CCR &= ~DMA_CCR_PINC;

how it works?

Refer https://medium.com/@csrohit/working-with-usart-and-dma-in-stm32-arm-cortex-m3-6a0e8b3174f3