正确理解STM32H7支持的硬件串口FIFO空间大小

eric2013

手册中介绍是发送和接收各带了16个：




为了方便支持串口的9bit数据长度，8bit数据长度和7bit数据长度，FIFO是支持bit操作的。

即上面截图的16个是指可以处理16个9bit的数据长度串口数据，当然处理8bit和7bit更没问题。

根据参考手册说明，TxFIFO大小是16*9bit，而RxFIFO大小是16*12bit。

HAL库的处理：

1. static void UARTEx_SetNbDataToProcess(UART_HandleTypeDef *huart)
   
2. {
   
3.   uint8_t rx_fifo_depth;
   
4.   uint8_t tx_fifo_depth;
   
5.   uint8_t rx_fifo_threshold;
   
6.   uint8_t tx_fifo_threshold;
   
7.   uint8_t numerator[] = {1U, 1U, 1U, 3U, 7U, 1U, 0U, 0U};
   
8.   uint8_t denominator[] = {8U, 4U, 2U, 4U, 8U, 1U, 1U, 1U};
   
9. 
   
10.   if (huart->FifoMode == UART_FIFOMODE_DISABLE)
    
11.   {
    
12.     huart->NbTxDataToProcess = 1U;
    
13.     huart->NbRxDataToProcess = 1U;
    
14.   }
    
15.   else
    
16.   {
    
17.     rx_fifo_depth = RX_FIFO_DEPTH;
    
18.     tx_fifo_depth = TX_FIFO_DEPTH;
    
19.     rx_fifo_threshold = (uint8_t)(READ_BIT(huart->Instance->CR3, USART_CR3_RXFTCFG) >> USART_CR3_RXFTCFG_Pos);
    
20.     tx_fifo_threshold = (uint8_t)(READ_BIT(huart->Instance->CR3, USART_CR3_TXFTCFG) >> USART_CR3_TXFTCFG_Pos);
    
21.     huart->NbTxDataToProcess = ((uint16_t)tx_fifo_depth * numerator[tx_fifo_threshold]) / (uint16_t)denominator[tx_fifo_threshold];
    
22.     huart->NbRxDataToProcess = ((uint16_t)rx_fifo_depth * numerator[rx_fifo_threshold]) / (uint16_t)denominator[rx_fifo_threshold];
    
23.   }
    
24. }

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eric2013

中断里面的处理：

1. /**
   
2.   * @brief TX interrrupt handler for 7 or 8 bits data word length and FIFO mode is enabled.
   
3.   * @note   Function is called under interruption only, once
   
4.   *         interruptions have been enabled by HAL_UART_Transmit_IT().
   
5.   * @param huart UART handle.
   
6.   * @retval None
   
7.   */
   
8. static void UART_TxISR_8BIT_FIFOEN(UART_HandleTypeDef *huart)
   
9. {
   
10.   uint16_t  nb_tx_data;
    
11. 
    
12.   /* Check that a Tx process is ongoing */
    
13.   if (huart->gState == HAL_UART_STATE_BUSY_TX)
    
14.   {
    
15.     for (nb_tx_data = huart->NbTxDataToProcess ; nb_tx_data > 0U ; nb_tx_data--)
    
16.     {
    
17.       if (huart->TxXferCount == 0U)
    
18.       {
    
19.         /* Disable the TX FIFO threshold interrupt */
    
20.         CLEAR_BIT(huart->Instance->CR3, USART_CR3_TXFTIE);
    
21. 
    
22.         /* Enable the UART Transmit Complete Interrupt */
    
23.         SET_BIT(huart->Instance->CR1, USART_CR1_TCIE);
    
24. 
    
25.         break; /* force exit loop */
    
26.       }
    
27.       else if (READ_BIT(huart->Instance->ISR, USART_ISR_TXE_TXFNF) != 0U)
    
28.       {
    
29.         huart->Instance->TDR = (uint8_t)(*huart->pTxBuffPtr & (uint8_t)0xFF);
    
30.         huart->pTxBuffPtr++;
    
31.         huart->TxXferCount--;
    
32.       }
    
33.       else
    
34.       {
    
35.         /* Nothing to do */
    
36.       }
    
37.     }
    
38.   }
    
39. }
    
40. 
    
41. /**
    
42.   * @brief TX interrrupt handler for 9 bits data word length and FIFO mode is enabled.
    
43.   * @note   Function is called under interruption only, once
    
44.   *         interruptions have been enabled by HAL_UART_Transmit_IT().
    
45.   * @param huart UART handle.
    
46.   * @retval None
    
47.   */
    
48. static void UART_TxISR_16BIT_FIFOEN(UART_HandleTypeDef *huart)
    
49. {
    
50.   uint16_t *tmp;
    
51.   uint16_t  nb_tx_data;
    
52. 
    
53.   /* Check that a Tx process is ongoing */
    
54.   if (huart->gState == HAL_UART_STATE_BUSY_TX)
    
55.   {
    
56.     for (nb_tx_data = huart->NbTxDataToProcess ; nb_tx_data > 0U ; nb_tx_data--)
    
57.     {
    
58.       if (huart->TxXferCount == 0U)
    
59.       {
    
60.         /* Disable the TX FIFO threshold interrupt */
    
61.         CLEAR_BIT(huart->Instance->CR3, USART_CR3_TXFTIE);
    
62. 
    
63.         /* Enable the UART Transmit Complete Interrupt */
    
64.         SET_BIT(huart->Instance->CR1, USART_CR1_TCIE);
    
65. 
    
66.         break; /* force exit loop */
    
67.       }
    
68.       else if (READ_BIT(huart->Instance->ISR, USART_ISR_TXE_TXFNF) != 0U)
    
69.       {
    
70.         tmp = (uint16_t *) huart->pTxBuffPtr;
    
71.         huart->Instance->TDR = (((uint32_t)(*tmp)) & 0x01FFUL);
    
72.         huart->pTxBuffPtr += 2U;
    
73.         huart->TxXferCount--;
    
74.       }
    
75.       else
    
76.       {
    
77.         /* Nothing to do */
    
78.       }
    
79.     }
    
80.   }
    
81. }

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wsr2580

请问在STM32中有人说DMA存在FIFO，而有的人说UART存在FIFO，看上面的代码是对串口的FIFO进行设置，请问有DMA存在FIFO的情况吗？还是前面说的是一个意思？

eric2013

wsr2580 发表于 2023-4-12 14:55
请问在STM32中有人说DMA存在FIFO，而有的人说UART存在FIFO，看上面的代码是对串口的FIFO进行设置，请问有DM ...

H7系列的UART你们有硬件FIFO
DMA也是有FIFO的，DMA的FIFO作用