stm32f407 usart6 dma rx

To configure USART6 with DMA RX on STM32F407, follow these steps:

1. Enable RCC USART6 clock:

   RCC->APB2ENR |= RCC_APB2ENR_USART6EN;

2. Enable DMA2 clock:

   RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN;

3. Configure GPIO pins for USART6:

   // Configure GPIO pins for USART6
   GPIOC->MODER |= GPIO_MODER_MODE6_1 | GPIO_MODER_MODE7_1;
   GPIOC->AFR[0] |= GPIO_AF8_USART6 << GPIO_AFRL_AFRL6_Pos |
                     GPIO_AF8_USART6 << GPIO_AFRL_AFRL7_Pos;
   GPIOC->OSPEEDR |= GPIO_OSPEEDR_OSPEED6 | GPIO_OSPEEDR_OSPEED7;

4. Configure USART6:

   USART6->CR1 &= ~USART_CR1_UE; // Disable USART6
   USART6->CR1 |= USART_CR1_RE;  // Enable receiver
   USART6->BRR = 0x138;          // Set baud rate to 115200
   USART6->CR3 |= USART_CR3_DMAR; // Enable DMA receiver
   USART6->CR1 |= USART_CR1_UE;  // Enable USART6

5. Configure DMA2 stream 1 for USART6 RX:

   DMA2_Stream1->CR &= ~DMA_SxCR_EN; // Disable DMA2 stream 1
   DMA2_Stream1->PAR = (uint32_t)&USART6->DR; // Peripheral address
   DMA2_Stream1->M0AR = (uint32_t)rx_buffer; // Memory address
   DMA2_Stream1->NDTR = BUFFER_SIZE; // Number of data to transfer
   DMA2_Stream1->CR |= DMA_SxCR_CHSEL_2 | DMA_SxCR_CHSEL_1 | DMA_SxCR_CHSEL_0; // Channel 5
   DMA2_Stream1->CR |= DMA_SxCR_PL_0; // Priority level: medium
   DMA2_Stream1->CR |= DMA_SxCR_MINC | DMA_SxCR_CIRC; // Memory increment mode, circular mode
   DMA2_Stream1->CR |= DMA_SxCR_DIR_0; // Peripheral-to-memory direction
   DMA2_Stream1->CR |= DMA_SxCR_TCIE; // Transfer complete interrupt enable
   DMA2_Stream1->CR |= DMA_SxCR_EN; // Enable DMA2 stream 1

6. Start USART6 reception:

   USART6->SR &= ~USART_SR_RXNE; // Clear RXNE flag
   USART6->CR1 |= USART_CR1_RE; // Enable receiver

7. Wait for DMA transfer complete interrupt:

   while (!dma_transfer_complete);
   dma_transfer_complete = 0; // Reset flag

8. Process received data:

   void DMA2_Stream1_IRQHandler(void)
   {
       if (DMA2->LISR & DMA_LISR_TCIF1)
       {
           DMA2->LIFCR |= DMA_LIFCR_CTCIF1; // Clear transfer complete flag
           dma_transfer_complete = 1; // Set flag
       }
   }

Note: `rx_buffer` is an array to store received data, and `BUFFER_SIZE` is its size. `dma_transfer_complete` is a flag to indicate DMA transfer complete interrupt. You can process received data in the main loop after the flag is set.