解决基于STM32H743问题——串口收发

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STMCU小助手发布时间：2023-3-11 22:40

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文章简介:	解决基于STM32H743问题——串口收发

在使用1.2版本的HAL库开发STM32H743的串口7设备的时候，遇到了如下问题：
数据发送使用HAL_UART_Transmit进行发送，单独测试发送的时候，发送正常。
接收则是HAL_UART_Receive_IT，逐字节进行接收并存放至数组，配合定时器进行不定长数据接收，单独测试接收的时候，接收也正常。
然后博主这里就把TX和RX短接，按理说在发送完成后的50ms以内就会打印接收到的数据（定时器设置的50ms溢出，即不定长数据间隔为50ms），但是这里并没有看到输出。

研究了下源码，可以发现，发送的时候，会把串口状态huart->gState标记为发送忙HAL_UART_STATE_BUSY_TX并上锁。

HAL_StatusTypeDef HAL_UART_Transmit(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout)
{
uint16_t* tmp;
uint32_t tickstart = 0U;
/* Check that a Tx process is not already ongoing */
if(huart->gState == HAL_UART_STATE_READY)
{
if((pData == NULL ) || (Size == 0U))
{
return HAL_ERROR;
}
/* Process Locked */
__HAL_LOCK(huart);
huart->ErrorCode = HAL_UART_ERROR_NONE;
huart->gState = HAL_UART_STATE_BUSY_TX;
/* Init tickstart for timeout managment*/
tickstart = HAL_GetTick();
huart->TxXferSize = Size;
huart->TxXferCount = Size;
while(huart->TxXferCount > 0U)
{
huart->TxXferCount--;
if(UART_WaitOnFlagUntilTimeout(huart, UART_FLAG_TXE, RESET, tickstart, Timeout) != HAL_OK)
{
return HAL_TIMEOUT;
}
if ((huart->Init.WordLength == UART_WORDLENGTH_9B) && (huart->Init.Parity == UART_PARITY_NONE))
{
tmp = (uint16_t*) pData;
huart->Instance->TDR = (*tmp & (uint16_t)0x01FFU);
pData += 2U;
}
else
{
huart->Instance->TDR = (*pData++ & (uint8_t)0xFFU);
}
}
if(UART_WaitOnFlagUntilTimeout(huart, UART_FLAG_TC, RESET, tickstart, Timeout) != HAL_OK)
{
return HAL_TIMEOUT;
}
/* At end of Tx process, restore huart->gState to Ready */
huart->gState = HAL_UART_STATE_READY;
/* Process Unlocked */
__HAL_UNLOCK(huart);
return HAL_OK;
}
else
{
return HAL_BUSY;
}
}

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而接收中断触发后，中断向量入口UART7_IRQHandler会直接调用HAL_UART_IRQHandler(&huart7)分析中断请求，根据接收数据完成请求函数调用UART_Receive_IT(huart)，注意这里会把huart->RxState设置为准备接收HAL_UART_STATE_READY并上锁。

HAL_StatusTypeDef HAL_UART_Receive_IT(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size)
{
/* Check that a Rx process is not already ongoing */
if(huart->RxState == HAL_UART_STATE_READY)
{
if((pData == NULL ) || (Size == 0U))
{
return HAL_ERROR;
}
/* Process Locked */
__HAL_LOCK(huart);
huart->pRxBuffPtr = pData;
huart->RxXferSize = Size;
huart->RxXferCount = Size;
/* Computation of UART mask to apply to RDR register */
UART_MASK_COMPUTATION(huart);
huart->ErrorCode = HAL_UART_ERROR_NONE;
huart->RxState = HAL_UART_STATE_BUSY_RX;
/* Process Unlocked */
__HAL_UNLOCK(huart);
/* Enable the UART Error Interrupt: (Frame error, noise error, overrun error) */
SET_BIT(huart->Instance->CR3, USART_CR3_EIE);
/* Enable the UART Parity Error interupt and RX FIFO Threshold interrupt
(if FIFO mode is enabled) or Data Register Not Empty interrupt
(if FIFO mode is disabled).
*/
if (READ_BIT(huart->Instance->CR1, USART_CR1_FIFOEN) != RESET)
{
SET_BIT(huart->Instance->CR1, USART_CR1_PEIE);
SET_BIT(huart->Instance->CR3, USART_CR3_RXFTIE);
}
else
{
SET_BIT(huart->Instance->CR1, USART_CR1_PEIE | USART_CR1_RXNEIE);
}
return HAL_OK;
}
else
{
return HAL_BUSY;
}
}

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查看一下定义，可以发现这里的一个设计缺陷，gState代表发送状态，RxState代表接收状态，通过这个状态机来保证接收和发送过程的完整性，但是，只设计了一把锁Lock，而锁是用来保护发送或者接收单个字节的完整性的，这样就导致了在连续发送的过程中，处理接收来的数据发现串口设备被上锁了，返回busy，从而丢失了发送的数据。

typedef struct
{
USART_TypeDef *Instance; /*!< UART registers base address */
UART_InitTypeDef Init; /*!< UART communication parameters */
UART_AdvFeatureInitTypeDef AdvancedInit; /*!< UART Advanced Features initialization parameters */
uint8_t *pTxBuffPtr; /*!< Pointer to UART Tx transfer Buffer */
uint16_t TxXferSize; /*!< UART Tx Transfer size */
__IO uint16_t TxXferCount; /*!< UART Tx Transfer Counter */
uint8_t *pRxBuffPtr; /*!< Pointer to UART Rx transfer Buffer */
uint16_t RxXferSize; /*!< UART Rx Transfer size */
__IO uint16_t RxXferCount; /*!< UART Rx Transfer Counter */
uint16_t Mask; /*!< UART Rx RDR register mask */
DMA_HandleTypeDef *hdmatx; /*!< UART Tx DMA Handle parameters */
DMA_HandleTypeDef *hdmarx; /*!< UART Rx DMA Handle parameters */
HAL_LockTypeDef Lock; /*!< Locking object */
__IO HAL_UART_StateTypeDef gState; /*!< UART state information related to global Handle management
and also related to Tx operations.
This parameter can be a value of @ref HAL_UART_StateTypeDef */
__IO HAL_UART_StateTypeDef RxState; /*!< UART state information related to Rx operations.
This parameter can be a value of @ref HAL_UART_StateTypeDef */
__IO uint32_t ErrorCode; /*!< UART Error code */
}UART_HandleTypeDef;