单片机 (MCU) 如何才能不死机之 串口(UART) Overrun

闲言少叙，先上Code。

大家看一下下面这段代码有没有问题？

#include "main.h"

static __IO uint32_t TimingDelay;

RCC_ClocksTypeDef RCC_Clocks;

uint8_t uart_buffer[100];

// GPIO Configuration

void GPIO_Configuration(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_1); // Tx PA9

GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_1); // Rx PA10

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; // USART1_TX | USART1_RX

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_Level_1;

GPIO_Init(GPIOA, &GPIO_InitStructure);

}

// USART Configuration

void USART_Configuration(void)

{

USART_InitTypeDef USART_InitStructure;

USART_InitStructure.USART_BaudRate = 115200;

//USART_InitStructure.USART_BaudRate = 9600;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;

USART_Init(USART1,&USART_InitStructure);

USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

USART_Cmd(USART1,ENABLE);

}

// Interrupt Configuration

void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

// USART1 interrupt Config

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

// USART1 Interrupt Handler

void USART1_IRQHandler (void)

{

static uint8_t i = 0;

if(USART_GetITStatus(USART1,USART_IT_RXNE)!= RESET)

{// Clear Receive Data Register Not Empty Flag

USART_ClearITPendingBit(USART1,USART_IT_RXNE);

uart_buffer[i++] = USART_ReceiveData(USART1);

if(i == 100)

i = 0;

}

}

int main(void)

{

static uint8_t ch;

// Init a 1ms timer interrupt, for Delay function implementation.

RCC_GetClocksFreq(&RCC_Clocks);

SysTick_Config(RCC_Clocks.HCLK_Frequency / 1000);

// Enable USART1 and GPIOA clock

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE);

GPIO_Configuration();

USART_Configuration();

NVIC_Configuration();

ch = 'A';

while(1)

{

Delay(50);

while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

USART_SendData(USART1, ch);

ch++;

}

}

void Delay(__IO uint32_t nTime)

{

TimingDelay = nTime;

while(TimingDelay != 0);

}

void TimingDelay_Decrement(void)

{

if(TimingDelay != 0x00)

{

TimingDelay--;

}

}

它是可以在 STM32F030 上调试通过的串口收发测试程序，发送采用延时循环，接收采用中断，接收到的数据存入缓冲区。

有很多比较认真的实战派的同学估计会下载到板子上跑一跑，它确实能跑通，看起来也没什么问题。很多教程甚至官方的代码都是类似的处理方法。

但这确实有点儿像陷马坑，看似一马平川，跑着跑着突然连马带人 kucha 一声掉坑里了。这还真不是开玩笑，某知名楼宇自控公司的产品就在安装到

客户现场后，经常莫名奇妙的死机。查来查去，查去查来，才发现问题。可是解决起来不容易啊，一个一个的去拆开，更新代码，想想都。。。

所以同学们不要轻视任何一段代码啊！

这段代码的问题是，如果接收数据之间间隔时间较长，可以正常收数据。但是如果对方发送数据非常快，或者偶尔在自己还没从串口接收寄存器取走数据

的时候突然又来了数据，会导致 Overrun 标志位的置位。这个标志位一置，串口基本上就罢工了。所以，在程序中一定要有对异常情况的处理。甚至觉得不会

发生的异常也不要置之不理。（想一想为什么要填充Flash的空白区域？在正常情况下代码永远不会跑到空白区域是吧。）

对串口异常的处理可以参考下面的代码。当然也可以在主程序中定时处理，以便在中断失效的情况下还能恢复。

#include "main.h"

// TopSemic

// Note: USART demo code runs on STM32F030

static __IO uint32_t TimingDelay;

RCC_ClocksTypeDef RCC_Clocks;

uint8_t uart_buffer[100];

// GPIO Configuration

void GPIO_Configuration(void)

{

GPIO_InitTypeDef GPIO_InitStructure;

GPIO_PinAFConfig(GPIOA,GPIO_PinSource9,GPIO_AF_1); // Tx PA9

GPIO_PinAFConfig(GPIOA,GPIO_PinSource10,GPIO_AF_1); // Rx PA10

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9 | GPIO_Pin_10; // USART1_TX | USART1_RX

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;

GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;

GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_Level_1;

GPIO_Init(GPIOA, &GPIO_InitStructure);

}

// USART Configuration

void USART_Configuration(void)

{

USART_InitTypeDef USART_InitStructure;

USART_InitStructure.USART_BaudRate = 115200;

//USART_InitStructure.USART_BaudRate = 9600;

USART_InitStructure.USART_WordLength = USART_WordLength_8b;

USART_InitStructure.USART_StopBits = USART_StopBits_1;

USART_InitStructure.USART_Parity = USART_Parity_No;

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;

USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;

USART_Init(USART1,&USART_InitStructure);

USART_ITConfig(USART1, USART_IT_RXNE, ENABLE);

USART_Cmd(USART1,ENABLE);

}

// Interrupt Configuration

void NVIC_Configuration(void)

{

NVIC_InitTypeDef NVIC_InitStructure;

// USART1 interrupt Config

NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;

NVIC_InitStructure.NVIC_IRQChannelPriority = 0;

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;

NVIC_Init(&NVIC_InitStructure);

}

// USART1 Interrupt Handler

void USART1_IRQHandler (void)

{

static uint8_t i = 0;

if(USART_GetFlagStatus(USART1, USART_FLAG_ORE) != RESET)

{// Clear Overrun Error Flag

USART_ClearFlag(USART1, USART_FLAG_ORE);

}

else if(USART_GetFlagStatus(USART1, USART_FLAG_NE) != RESET)

{// Clear Noise Error Flag

USART_ClearFlag(USART1, USART_FLAG_NE);

}

else if(USART_GetFlagStatus(USART1, USART_FLAG_FE) != RESET)

{// Clear Framing Error Flag

USART_ClearFlag(USART1, USART_FLAG_FE);

}

else if(USART_GetFlagStatus(USART1, USART_FLAG_PE) != RESET)

{// Clear Parity Error Flag

USART_ClearFlag(USART1, USART_FLAG_PE);

}

else if(USART_GetITStatus(USART1,USART_IT_RXNE)!= RESET)

{// Clear Receive Data Register Not Empty Flag

USART_ClearITPendingBit(USART1,USART_IT_RXNE);

uart_buffer[i++] = USART_ReceiveData(USART1);

if(i == 100)

i = 0;

}

}

int main(void)

{

static uint8_t ch;

// Init a 1ms timer interrupt, for Delay function implementation.

RCC_GetClocksFreq(&RCC_Clocks);

SysTick_Config(RCC_Clocks.HCLK_Frequency / 1000);

// Enable USART1 and GPIOA clock

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);

RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOA,ENABLE);

GPIO_Configuration();

USART_Configuration();

NVIC_Configuration();

ch = 'A';

while(1)

{

Delay(50);

while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);

USART_SendData(USART1, ch);

ch++;

}

}

/**

* @brief Inserts a delay time.

* @param nTime: specifies the delay time length, in 1 ms.

* @retval None

*/

void Delay(__IO uint32_t nTime)

{

TimingDelay = nTime;

while(TimingDelay != 0);

}

/**

* @brief Decrements the TimingDelay variable.

* @param None

* @retval None

*/

void TimingDelay_Decrement(void)

{

if(TimingDelay != 0x00)

{

TimingDelay--;

}

}