STM32的串口2波特率原设置为38400，但改成9600后，另一个IO口控制不了LED闪灯

冰冷de名人

我用的MCU是STM32F103C8，用了一个IO口来控制LED的闪烁，用串口2来发送数据，当我的串口2波特率设置为38400时，全部正常，LED灯是可以正常闪烁的，但改成9600后，控制LED的IO口就一直输出为高了，本来是要拉低它LED才会亮的，这是什么原因啊？我用 if((lenx % 500)==0)LED0=!LED0;    这一句来翻转LED～求大神指点！

正点原子

估计是波特率设置有问题。

冰冷de名人

回复【2楼】正点原子:
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原子哥，我的那个串口2的代码是参考你蓝牙模块实验上面的代码，就那个超时我修改成了20ms，其它基本一样（如下面），然后用了   USART2_Init(38400)； 这一句来设置波特率，这样有其它问题吗？


#include "delay.h"
#include "usart2.h"
#include "stdarg.h"    
#include "stdio.h"    
#include "string.h"    




//????·????????? 
__align(8) u8 USART2_TX_BUF[USART2_MAX_SEND_LEN];  //·???????,×??óUSART2_MAX_SEND_LEN×???




#ifdef USART2_RX_EN    //??????????????      
//?????????????? 
u8 USART2_RX_BUF[USART2_MAX_RECV_LEN];  //????????,×??óUSART2_MAX_RECV_LEN??×???.



//?¨??????????????2??×?·????????±???????ó??20ms?????¨????????????????????.
//????2??×?·?????????????20ms,?ò????????1??????????.??????????20ms??????????
//????????,?ò±í???????????ê±?.
//????????????×???
//[15]:0,??????????????;1,???????????ú????.
//[14:0]:?????????????¤??
u16 USART2_RX_STA=0;     
void USART2_IRQHandler(void)
{
u8 res;     
if(USART_GetITStatus(USART2, USART_IT_RXNE) != RESET)//??????????
{  
 
res =USART_ReceiveData(USART2);
if(USART2_RX_STA<USART2_MAX_RECV_LEN) //??????????????
{
TIM_SetCounter(TIM4,0);//?????÷????          
if(USART2_RX_STA==0)TIM4_Set(1);   //?????¨?±?÷4?????? 
USART2_RX_BUF[USART2_RX_STA++]=res; //??????????????  
}else 
{
USART2_RX_STA|=1<<15; //????±ê???????ê??
} 
}    
}   
//??????IO ????2
//pclk1CLK1?±??????(Mhz)
//bound:?¨????   
void USART2_Init(u32 bound)
{  

NVIC_InitTypeDef NVIC_InitStructure;
GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;

RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE); // GPIOA?±??
RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2,ENABLE);

  USART_DeInit(USART2);  //????????2
 //USART2_TX   A.2
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_2; //PA.2
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; //???????ì????
  GPIO_Init(GPIOA, &GPIO_InitStructure); //??????PA2
   
    //USART2_RX   A.3
  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_3;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//????????
  GPIO_Init(GPIOA, &GPIO_InitStructure);  //??????PA3

USART_InitStructure.USART_BaudRate = bound;//??°??è????9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;//×??¤??8??????????
USART_InitStructure.USART_StopBits = USART_StopBits_1;//??????????
USART_InitStructure.USART_Parity = USART_Parity_No;//?????????é??
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;//???????????÷????
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //??·?????
  
USART_Init(USART2, &USART_InitStructure); //?????????? 2
  
//?¨?????è??
 // USART2->BRR=(pclk1*1000000)/(bound);// ?¨?????è??  
//USART2->CR1|=0X200C;   //1??????,?????é??.
USART_DMACmd(USART2,USART_DMAReq_Tx,ENABLE);   //????????2??DMA·???
UART_DMA_Config(DMA1_Channel7,(u32)&USART2->DR,(u32)USART2_TX_BUF);//DMA1?¨??7,???è??????2,?????÷??USART2_TX_BUF 
USART_Cmd(USART2, ENABLE);                    //???????? 

#ifdef USART2_RX_EN    //??????????????
//????????????
  USART_ITConfig(USART2, USART_IT_RXNE, ENABLE);//????????   

NVIC_InitStructure.NVIC_IRQChannel = USART2_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=2 ;//??????????3
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3; //×???????3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ?¨??????
NVIC_Init(&NVIC_InitStructure); //?ù?????¨????????????VIC?????÷
TIM4_Init(199,7199); //20ms????
USART2_RX_STA=0; //????
TIM4_Set(0); //??±??¨?±?÷4
#endif  

}
//????2,printf ????
//?·±?????·?????????????USART2_MAX_SEND_LEN×???
void u2_printf(char* fmt,...)  
{  
va_list ap;
va_start(ap,fmt);
vsprintf((char*)USART2_TX_BUF,fmt,ap);
va_end(ap);
while(DMA_GetCurrDataCounter(DMA1_Channel7)!=0); //?????¨??7?????ê??   
UART_DMA_Enable(DMA1_Channel7,strlen((const char*)USART2_TX_BUF));  //?¨??dma·???????
}
//?¨?±?÷4????·??????ò     
void TIM4_IRQHandler(void)
{ 
if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET)//???ü??????
{      
USART2_RX_STA|=1<<15; //±ê???????ê??
TIM_ClearITPendingBit(TIM4, TIM_IT_Update  );  //????TIMx?ü??????±ê??    
TIM4_Set(0); //??±?TIM4  
}     
}
//?è??TIM4??????
//sta:0????±?;1,????;
void TIM4_Set(u8 sta)
{
if(sta)
{
       
TIM_SetCounter(TIM4,0);//?????÷????
TIM_Cmd(TIM4, ENABLE);  //????TIMx
}else TIM_Cmd(TIM4, DISABLE);//??±??¨?±?÷4    
}
//?¨???¨?±?÷??????????
//??????????????APB1??2±?????APB1??36M
//arr??×?????×°????
//psc???±???¤·?????  
void TIM4_Init(u16 arr,u16 psc)
{
NVIC_InitTypeDef NVIC_InitStructure;
TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); //?±??????//TIM4?±??????    

//?¨?±?÷TIM3??????
TIM_TimeBaseStructure.TIM_Period = arr; //?è???????????ü??????×°????????×?????×°???????÷????????
TIM_TimeBaseStructure.TIM_Prescaler =psc; //?è??????×÷??TIMx?±?????????????¤·?????
TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //?è???±??·???:TDTS = Tck_tim
TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM?ò??????????
TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); //?ù?????¨????????????TIMx???±???ù??????
 
TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE ); //???????¨??TIM4????,???í?ü??????

    
NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=1 ;//??????????3
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 2; //×???????3
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ?¨??????
NVIC_Init(&NVIC_InitStructure); //?ù?????¨????????????VIC?????÷

}
#endif  
///////////////////////////////////////USART2 DMA·?????????·?//////////////////////////////////         
//DMA1???÷?¨??????
//???????????????????¨??,???????ù?????????é????????
//???????÷->???è????/8???????í??/?????÷????????
//DMA_CHxMA?¨??CHx
//cpar:???è???·
//cmar:?????÷???·    
void UART_DMA_Config(DMA_Channel_TypeDef*DMA_CHx,u32 cpar,u32 cmar)
{
DMA_InitTypeDef DMA_InitStructure;
  RCC_AHBPeriphClockCmd(RCC_AHBPeriph_DMA1, ENABLE); //????DMA????
  DMA_DeInit(DMA_CHx);   //??DMA???¨??1?????÷???è???±????
DMA_InitStructure.DMA_PeripheralBaseAddr = cpar;  //DMA???èADC?ù???·
DMA_InitStructure.DMA_MemoryBaseAddr = cmar;  //DMA?????ù???·
DMA_InitStructure.DMA_DIR = DMA_DIR_PeripheralDST;  //????????·??ò????????????·????????è
DMA_InitStructure.DMA_BufferSize = 0;  //DMA?¨????DMA???????ó??
DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;  //???è???·?????÷??±?
DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;  //???????·?????÷????
DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;  //?????í????8??
DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte; //?????í????8??
DMA_InitStructure.DMA_Mode = DMA_Mode_Normal;  //?¤×÷??????????????
DMA_InitStructure.DMA_Priority = DMA_Priority_Medium; //DMA?¨?? x???????????? 
DMA_InitStructure.DMA_M2M = DMA_M2M_Disable;  //DMA?¨??x?????è??????????????????
DMA_Init(DMA_CHx, &DMA_InitStructure);  //?ù??DMA_InitStruct?????¨????????????DMA???¨??USART1_Tx_DMA_Channel?ù±ê?????????÷
} 
//????????DMA????
void UART_DMA_Enable(DMA_Channel_TypeDef*DMA_CHx,u8 len)
{
DMA_Cmd(DMA_CHx, DISABLE );  //??±? ???????¨??        
DMA_SetCurrDataCounter(DMA_CHx,len);//DMA?¨????DMA???????ó??
DMA_Cmd(DMA_CHx, ENABLE);           //????DMA????
}    
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////   

void uart2_Send_byte(u8 a) 
{
     USART2->DR = a;
         while(USART_GetFlagStatus(USART2, USART_FLAG_TXE) == RESET);
}

正点原子

没问题。你可以试试直接和电脑通讯OK不。