发新帖我要提问
返回列表
打印

固件库是如何操作控制寄存器USART_CR1的？

[复制链接]
5817|3
手机看帖
扫描二维码
随时随地手机跟帖
跳转到指定楼层
楼主
程序会不会|  楼主 | 2012-5-1 13:44 | 只看该作者 |只看大图 回帖奖励 |倒序浏览 |阅读模式
固件库, USART, 寄存器, 控制, 串口
写了一个STM32的串口实验程序，就是不断的向PC串口发数据，可是在手册里看到控制寄存器USART_CR1中TE和RE分别为发送和接受使能，就是说每次在发送和接受数据的时候必须要置位这两位，可是我在固件库（usart.c这个函数）并没有找到设置这两个控制位的函数，我用的是3.5版本的库，芯片用的是107VC;再问一个关于波特率的问题：
手册上那个关于波特率的计算公式：系统时钟赫兹和波特率的进率为多少啊，这两个量之间有什么关系呢？.........问了这么多苦了大伙了，哈哈

使用特权

评论回复 赏
沙发
logokfu| | 2012-5-1 14:04 | 只看该作者
本帖最后由 **kfu 于 2012-5-1 14:17 编辑

怎么会没有使能 TE和RE的函数呢，楼主看这里。



/**
  * @brief  Initializes the USARTx peripheral according to the specified
  *         parameters in the USART_InitStruct .
  * @param  USARTx: Select the USART or the UART peripheral.
  *   This parameter can be one of the following values:
  *   USART1, USART2, USART3, UART4 or UART5.
  * @param  USART_InitStruct: pointer to a USART_InitTypeDef structure
  *         that contains the configuration information for the specified USART
  *         peripheral.
  * @retval None
  */
void USART_Init(USART_TypeDef* USARTx, USART_InitTypeDef* USART_InitStruct)  //TE 和RE使能就在这个函数里面包含着的
{
  uint32_t tmpreg = 0x00, apbclock = 0x00;
  uint32_t integerdivider = 0x00;
  uint32_t fractionaldivider = 0x00;
  uint32_t usartxbase = 0;
  RCC_ClocksTypeDef RCC_ClocksStatus;
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_USART_BAUDRATE(USART_InitStruct->USART_BaudRate));  
  assert_param(IS_USART_WORD_LENGTH(USART_InitStruct->USART_WordLength));
  assert_param(IS_USART_STOPBITS(USART_InitStruct->USART_StopBits));
  assert_param(IS_USART_PARITY(USART_InitStruct->USART_Parity));
  assert_param(IS_USART_MODE(USART_InitStruct->USART_Mode));
  assert_param(IS_USART_HARDWARE_FLOW_CONTROL(USART_InitStruct->USART_HardwareFlowControl));
  /* The hardware flow control is available only for USART1, USART2 and USART3 */
  if (USART_InitStruct->USART_HardwareFlowControl != USART_HardwareFlowControl_None)
  {
    assert_param(IS_USART_123_PERIPH(USARTx));
  }
  usartxbase = (uint32_t)USARTx;
/*---------------------------- USART CR2 Configuration -----------------------*/
  tmpreg = USARTx->CR2;
  /* Clear STOP[13:12] bits */
  tmpreg &= CR2_STOP_CLEAR_Mask;
  /* Configure the USART Stop Bits, Clock, CPOL, CPHA and LastBit ------------*/
  /* Set STOP[13:12] bits according to USART_StopBits value */
  tmpreg |= (uint32_t)USART_InitStruct->USART_StopBits;
  
  /* Write to USART CR2 */
  USARTx->CR2 = (uint16_t)tmpreg;
/*---------------------------- USART CR1 Configuration -----------------------*/
  tmpreg = USARTx->CR1;
  /* Clear M, PCE, PS, TE and RE bits */
  tmpreg &= CR1_CLEAR_Mask;
  /* Configure the USART Word Length, Parity and mode ----------------------- */
  /* Set the M bits according to USART_WordLength value */
  /* Set PCE and PS bits according to USART_Parity value */
  /* Set TE and RE bits according to USART_Mode value */
  tmpreg |= (uint32_t)USART_InitStruct->USART_WordLength | USART_InitStruct->USART_Parity |
            USART_InitStruct->USART_Mode; //这里就是设置TE 和RE使能的地方。

  /* Write to USART CR1 */
  USARTx->CR1 = (uint16_t)tmpreg;
/*---------------------------- USART CR3 Configuration -----------------------*/  
  tmpreg = USARTx->CR3;
  /* Clear CTSE and RTSE bits */
  tmpreg &= CR3_CLEAR_Mask;
  /* Configure the USART HFC -------------------------------------------------*/
  /* Set CTSE and RTSE bits according to USART_HardwareFlowControl value */
  tmpreg |= USART_InitStruct->USART_HardwareFlowControl;
  /* Write to USART CR3 */
  USARTx->CR3 = (uint16_t)tmpreg;
/*---------------------------- USART BRR Configuration -----------------------*/
  /* Configure the USART Baud Rate -------------------------------------------*/
  RCC_GetClocksFreq(&RCC_ClocksStatus);
  if (usartxbase == USART1_BASE)
  {
    apbclock = RCC_ClocksStatus.PCLK2_Frequency;
  }
  else
  {
    apbclock = RCC_ClocksStatus.PCLK1_Frequency;
  }
  
  /* Determine the integer part */
  if ((USARTx->CR1 & CR1_OVER8_Set) != 0)
  {
    /* Integer part computing in case Oversampling mode is 8 Samples */
    integerdivider = ((25 * apbclock) / (2 * (USART_InitStruct->USART_BaudRate)));   
  }
  else /* if ((USARTx->CR1 & CR1_OVER8_Set) == 0) */
  {
    /* Integer part computing in case Oversampling mode is 16 Samples */
    integerdivider = ((25 * apbclock) / (4 * (USART_InitStruct->USART_BaudRate)));   
  }
  tmpreg = (integerdivider / 100) << 4;
  /* Determine the fractional part */
  fractionaldivider = integerdivider - (100 * (tmpreg >> 4));
  /* Implement the fractional part in the register */
  if ((USARTx->CR1 & CR1_OVER8_Set) != 0)
  {
    tmpreg |= ((((fractionaldivider * 8) + 50) / 100)) & ((uint8_t)0x07);
  }
  else /* if ((USARTx->CR1 & CR1_OVER8_Set) == 0) */
  {
    tmpreg |= ((((fractionaldivider * 16) + 50) / 100)) & ((uint8_t)0x0F);
  }
  
  /* Write to USART BRR */
  USARTx->BRR = (uint16_t)tmpreg;
}

使用特权

评论回复 赏
板凳
程序会不会|  楼主 | 2012-5-1 14:19 | 只看该作者
看到了，丢人啊 ，那那个波特率的问题呢？就知道lofokfu大侠会回答我的提问，哈哈，向热心人士致敬 哈哈:kiss: 2# **kfu

使用特权

评论回复 赏
地板
logokfu| | 2012-5-1 17:02 | 只看该作者
本帖最后由 **kfu 于 2012-5-1 17:03 编辑

这个不应该叫进率问题吧，呵呵。

你看这里，这个手册上说的。





/**
  * @brief  Initializes the USARTx peripheral according to the specified
  *         parameters in the USART_InitStruct .
  * @param  USARTx: Select the USART or the UART peripheral.
  *   This parameter can be one of the following values:
  *   USART1, USART2, USART3, UART4 or UART5.
  * @param  USART_InitStruct: pointer to a USART_InitTypeDef structure
  *         that contains the configuration information for the specified USART
  *         peripheral.
  * @retval None
  */
void USART_Init(USART_TypeDef* USARTx, USART_InitTypeDef* USART_InitStruct)  //TE 和RE使能就在这个函数里面包含着的
{
  uint32_t tmpreg = 0x00, apbclock = 0x00;
  uint32_t integerdivider = 0x00;
  uint32_t fractionaldivider = 0x00;
  uint32_t usartxbase = 0;
  RCC_ClocksTypeDef RCC_ClocksStatus;
  /* Check the parameters */
  assert_param(IS_USART_ALL_PERIPH(USARTx));
  assert_param(IS_USART_BAUDRATE(USART_InitStruct->USART_BaudRate));  
  assert_param(IS_USART_WORD_LENGTH(USART_InitStruct->USART_WordLength));
  assert_param(IS_USART_STOPBITS(USART_InitStruct->USART_StopBits));
  assert_param(IS_USART_PARITY(USART_InitStruct->USART_Parity));
  assert_param(IS_USART_MODE(USART_InitStruct->USART_Mode));
  assert_param(IS_USART_HARDWARE_FLOW_CONTROL(USART_InitStruct->USART_HardwareFlowControl));
  /* The hardware flow control is available only for USART1, USART2 and USART3 */
  if (USART_InitStruct->USART_HardwareFlowControl != USART_HardwareFlowControl_None)
  {
    assert_param(IS_USART_123_PERIPH(USARTx));
  }
  usartxbase = (uint32_t)USARTx;
/*---------------------------- USART CR2 Configuration -----------------------*/
  tmpreg = USARTx->CR2;
  /* Clear STOP[13:12] bits */
  tmpreg &= CR2_STOP_CLEAR_Mask;
  /* Configure the USART Stop Bits, Clock, CPOL, CPHA and LastBit ------------*/
  /* Set STOP[13:12] bits according to USART_StopBits value */
  tmpreg |= (uint32_t)USART_InitStruct->USART_StopBits;
  
  /* Write to USART CR2 */
  USARTx->CR2 = (uint16_t)tmpreg;
/*---------------------------- USART CR1 Configuration -----------------------*/
  tmpreg = USARTx->CR1;
  /* Clear M, PCE, PS, TE and RE bits */
  tmpreg &= CR1_CLEAR_Mask;
  /* Configure the USART Word Length, Parity and mode ----------------------- */
  /* Set the M bits according to USART_WordLength value */
  /* Set PCE and PS bits according to USART_Parity value */
  /* Set TE and RE bits according to USART_Mode value */
  tmpreg |= (uint32_t)USART_InitStruct->USART_WordLength | USART_InitStruct->USART_Parity |
            USART_InitStruct->USART_Mode; //这里就是设置TE 和RE使能的地方。

  /* Write to USART CR1 */
  USARTx->CR1 = (uint16_t)tmpreg;
/*---------------------------- USART CR3 Configuration -----------------------*/  
  tmpreg = USARTx->CR3;
  /* Clear CTSE and RTSE bits */
  tmpreg &= CR3_CLEAR_Mask;
  /* Configure the USART HFC -------------------------------------------------*/
  /* Set CTSE and RTSE bits according to USART_HardwareFlowControl value */
  tmpreg |= USART_InitStruct->USART_HardwareFlowControl;
  /* Write to USART CR3 */
  USARTx->CR3 = (uint16_t)tmpreg;
/*---------------------------- USART BRR Configuration --------*/  //这一段就是上面那个公式的体现，你可以自己debug一下就知道了。这里的算法我没有看懂，但是这个就是按照那个公式算的。
  /* Configure the USART Baud Rate -------------------------------------------*/
  RCC_GetClocksFreq(&RCC_ClocksStatus);
  if (usartxbase == USART1_BASE)
  {
    apbclock = RCC_ClocksStatus.PCLK2_Frequency;
  }
  else
  {
    apbclock = RCC_ClocksStatus.PCLK1_Frequency;
  }
  
  /* Determine the integer part */
  if ((USARTx->CR1 & CR1_OVER8_Set) != 0)
  {
    /* Integer part computing in case Oversampling mode is 8 Samples */
    integerdivider = ((25 * apbclock) / (2 * (USART_InitStruct->USART_BaudRate)));   
  }
  else /* if ((USARTx->CR1 & CR1_OVER8_Set) == 0) */
  {
    /* Integer part computing in case Oversampling mode is 16 Samples */
    integerdivider = ((25 * apbclock) / (4 * (USART_InitStruct->USART_BaudRate)));   
  }
  tmpreg = (integerdivider / 100) << 4;
  /* Determine the fractional part */
  fractionaldivider = integerdivider - (100 * (tmpreg >> 4));
  /* Implement the fractional part in the register */
  if ((USARTx->CR1 & CR1_OVER8_Set) != 0)
  {
    tmpreg |= ((((fractionaldivider * 8) + 50) / 100)) & ((uint8_t)0x07);
  }
  else /* if ((USARTx->CR1 & CR1_OVER8_Set) == 0) */
  {
    tmpreg |= ((((fractionaldivider * 16) + 50) / 100)) & ((uint8_t)0x0F);
  }
  
  /* Write to USART BRR */
  USARTx->BRR = (uint16_t)tmpreg;
}

使用特权

评论回复 赏
返回列表
发新帖 我要提问
高级模式
B Color Image Link Quote Code 收费 Smilies
您需要登录后才可以回帖 登录 | 注册

本版积分规则

程序会不会

46

主题

443

帖子

5

粉丝