因為晶片串列埠不夠用，只好用IO口模擬串列埠，在網上下載了個模擬串列埠的程式，可執行，但發現串列埠輸出隔幾個字元就會出現亂碼，主要部分程式碼如下：

#define OI_TXD	PAout(12)
#define OI_RXD	PAin(11)

#define BuadRate_9600	100

u8 len = 0;	//接收計數
u8 USART_buf[11];  //接收緩衝區

u8 recvStat = COM_STOP_BIT;
u8 recvData = 0;

void IO_TXD(u8 Data)
{
	u8 i = 0;
	OI_TXD = 0;  
	delay_us(BuadRate_9600);
	for(i = 0; i < 8; i++)
	{
		if(Data&0x01)
			OI_TXD = 1;  
		else
			OI_TXD = 0; 	
		
		delay_us(BuadRate_9600);
		Data = Data>>1;
	}
	OI_TXD = 1;
	delay_us(BuadRate_9600);
}
	
void USART_Send(u8 *buf, u8 len)
{
	u8 t;
	for(t = 0; t < len; t++)
	{
		IO_TXD(buf[t]);
	}
}
	
 void IOConfig(void)
 {
	GPIO_InitTypeDef  GPIO_InitStructure;
	NVIC_InitTypeDef NVIC_InitStructure;
 	EXTI_InitTypeDef EXTI_InitStruct;
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO|RCC_APB2Periph_GPIOA, ENABLE);	 //使能PB,PC埠時鐘 
	 
	 //SoftWare Serial TXD
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12;	    
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; 		 //推輓輸出
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;		 //IO口速度為50MHz	 
  GPIO_Init(GPIOA, &GPIO_InitStructure);	  				
  GPIO_SetBits(GPIOA,GPIO_Pin_12); 						
	 
	 
	//SoftWare Serial RXD
	GPIO_InitStructure.GPIO_Pin = GPIO_Pin_11;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;		
	GPIO_Init(GPIOA, &GPIO_InitStructure);	 

	GPIO_EXTILineConfig(GPIO_PortSourceGPIOA, GPIO_PinSource11);
	EXTI_InitStruct.EXTI_Line = EXTI_Line11;
	EXTI_InitStruct.EXTI_Mode=EXTI_Mode_Interrupt;
	EXTI_InitStruct.EXTI_Trigger=EXTI_Trigger_Falling; //下降沿觸發中斷
	EXTI_InitStruct.EXTI_LineCmd=ENABLE;
	EXTI_Init(&EXTI_InitStruct);


	NVIC_InitStructure.NVIC_IRQChannel= EXTI15_10_IRQn ; 
	NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=2; 
	NVIC_InitStructure.NVIC_IRQChannelSubPriority =2;  
	NVIC_InitStructure.NVIC_IRQChannelCmd=ENABLE;  
	NVIC_Init(&NVIC_InitStructure);  
	
}
 

 int main(void)
 {		
	delay_init();
        IOConfig();
        while(1)
	{
		USART_Send("100",3);
		delay_ms(100);
	}
}

void USART_Send(u8 *buf, u8 len)
{
	u8 t;
	for(t = 0; t < len; t++)
	{
		IO_TXD(buf[t]);
		delay_ms(1);
	}
}