串口DMA接收，哪里是接收数据存放处？

只看该作者 · 2020-2-14 10:47

/* Configure the DMA handler for reception process */
  hdma_rx.Instance                = USARTx_RX_DMA_STREAM;
  hdma_rx.Init.Request          = USARTx_RX_DMA_CHANNEL;
  hdma_rx.Init.Direction          = DMA_PERIPH_TO_MEMORY;
  hdma_rx.Init.PeriphInc          = DMA_PINC_DISABLE;
  hdma_rx.Init.MemInc             = DMA_MINC_ENABLE;
  hdma_rx.Init.PeriphDataAlignment = DMA_PDATAALIGN_BYTE;
  hdma_rx.Init.MemDataAlignment = DMA_MDATAALIGN_BYTE;
  hdma_rx.Init.Mode             = DMA_NORMAL;
  hdma_rx.Init.Priority          = DMA_PRIORITY_HIGH;
  hdma_rx.Init.FIFOMode          = DMA_FIFOMODE_DISABLE;
  hdma_rx.Init.FIFOThreshold    = DMA_FIFO_THRESHOLD_FULL;
  hdma_rx.Init.MemBurst          = DMA_MBURST_INC4;
  hdma_rx.Init.PeriphBurst       = DMA_PBURST_INC4;

  HAL_DMA_Init(&hdma_rx);

只看该作者 · 2020-2-17 14:30

这只是初始化，还没调用 HAL_UART_Receive_DMA 函数。[em:3:

只看该作者 · 2020-2-18 15:24

/* Clean D-cache */
/* Make sure the address is 32-byte aligned and add 32-bytes to length, in case it overlaps cacheline */
SCB_CleanDCache_by_Addr((uint32_t*)(((uint32_t)tx_buffer) & ~(uint32_t)0x1F), TX_LENGTH+32);

/* Start DMA transfer */
HAL_UART_Transmit_DMA(&huart1, tx_buffer, TX_LENGTH);
请问 SCB_Clean... 这语句什么意思？没这条就发不出

只看该作者 · 2020-2-18 15:32

DMA cpu不经过外设的内存直接访问单元吧？

只看该作者 · 2020-2-18 16:00

Transmitting data:

#define TX_LENGTH (16)
uint8_t tx_buffer[TX_LENGTH];

/* Write data */
tx_buffer[0] = 0x0;
tx_buffer[1] = 0x1;

/* Clean D-cache */
/* Make sure the address is 32-byte aligned and add 32-bytes to length, in case it overlaps cacheline */
SCB_CleanDCache_by_Addr((uint32_t*)(((uint32_t)tx_buffer) & ~(uint32_t)0x1F), TX_LENGTH+32);

/* Start DMA transfer */
HAL_UART_Transmit_DMA(&huart1, tx_buffer, TX_LENGTH);
Receiving data:

#define RX_LENGTH (16)
uint8_t rx_buffer[RX_LENGTH];

/* Invalidate D-cache before reception */
/* Make sure the address is 32-byte aligned and add 32-bytes to length, in case it overlaps cacheline */
SCB_InvalidateDCache_by_Addr((uint32_t*)(((uint32_t)rx_buffer) & ~(uint32_t)0x1F), RX_LENGTH+32);

/* Start DMA transfer */
HAL_UART_Receive_DMA(&huart1, rx_buffer, RX_LENGTH);
/* No access to rx_buffer should be made before DMA transfer is completed */

单收单发可以，同时收发数据出错