This program sets up a DMA transfer to send a string over UART. It simulates the DMA moving data from memory to UART data register. The output shows the string sent.
#include <stdint.h>
#include <stdbool.h>
#define BUFFER_SIZE 10
// Mock registers and bits for demonstration
volatile uint8_t UART_DR = 0;
volatile uint32_t DMA_CCR_EN = 1 << 0;
volatile uint32_t DMA_CCR_MINC = 1 << 1;
volatile uint32_t DMA_CCR_DIR = 1 << 4;
volatile uint32_t DMA_CCR_TCIE = 1 << 5;
volatile uint32_t USART_CR3_DMAR = 1 << 6;
volatile uint32_t USART_CR3_DMAT = 1 << 7;
// Simulated UART and DMA structures
typedef struct {
volatile uint32_t CR3;
volatile uint8_t DR;
} UART_TypeDef;
typedef struct {
volatile uint32_t CPAR;
volatile uint32_t CMAR;
volatile uint32_t CNDTR;
volatile uint32_t CCR;
} DMA_Channel_TypeDef;
UART_TypeDef UART1 = {0};
DMA_Channel_TypeDef DMA1_Channel4 = {0};
uint8_t tx_buffer[BUFFER_SIZE] = { 'H','e','l','l','o',' ','D','M','A','\0' };
uint8_t rx_buffer[BUFFER_SIZE] = {0};
void dma_uart_tx_start(UART_TypeDef *uart, DMA_Channel_TypeDef *dma, uint8_t *buffer, uint32_t size) {
dma->CPAR = (uint32_t)&uart->DR; // UART data register
dma->CMAR = (uint32_t)buffer; // memory buffer
dma->CNDTR = size; // number of bytes
dma->CCR = DMA_CCR_MINC | DMA_CCR_DIR | DMA_CCR_EN | DMA_CCR_TCIE; // enable DMA for memory to peripheral
uart->CR3 |= USART_CR3_DMAT; // enable UART DMA transmitter
}
int main() {
// Start DMA transfer of tx_buffer over UART1
dma_uart_tx_start(&UART1, &DMA1_Channel4, tx_buffer, BUFFER_SIZE);
// Simulate DMA transfer by copying data manually (for demo only)
for (int i = 0; i < BUFFER_SIZE; i++) {
UART1.DR = tx_buffer[i];
// Normally hardware moves data, here we just print
// Simulate sending each byte
// In real embedded code, UART DR register sends data
}
// Print what was sent
for (int i = 0; i < BUFFER_SIZE; i++) {
putchar(tx_buffer[i]);
}
putchar('\n');
return 0;
}
