STM32 IO模拟实现软件串口

最近项目中STM32的串口资源紧张，于是使用IO口进行模拟串口，现进行整理记录。

实现思路

IO口模拟串口的思路也比较简单，一切按照串口协议进行操作即可。

对于发送，计算好不同波特率对应的延时时间进行数据发送。

对于接收，稍微复杂。通过外部中断检测接收管脚的下降沿，检测到起始信号后开启定时器，定时器按照波特率设定好时间，每隔一段时间进入定时器中断接收数据，完成一个字节后关闭定时器。

测试Demo说明

TXD : PC13

RXD : PB14

波特率：9600 ，1-8-N

Demo功能

接收11个数据，然后把接收到的数据发送出去。

程序实现

#define OI_TXD PCout(13)

#define OI_RXD PBin(14)

#define BuadRate_9600 100

u8 len = 0; //接收计数

u8 USART_buf[11];  //接收缓冲区

enum{

COM_START_BIT,

COM_D0_BIT,

COM_D1_BIT,

COM_D2_BIT,

COM_D3_BIT,

COM_D4_BIT,

COM_D5_BIT,

COM_D6_BIT,

COM_D7_BIT,

COM_STOP_BIT,

};

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_GPIOB|RCC_APB2Periph_GPIOC, ENABLE); //使能PB,PC端口时钟 

//SoftWare Serial TXD

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;     

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; //推挽输出

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; //IO口速度为50MHz  

  GPIO_Init(GPIOC, &GPIO_InitStructure);  

  GPIO_SetBits(GPIOC,GPIO_Pin_13);

//SoftWare Serial RXD

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_14;

  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;

  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOB, &GPIO_InitStructure);  

GPIO_EXTILineConfig(GPIO_PortSourceGPIOB, GPIO_PinSource14);

EXTI_InitStruct.EXTI_Line = EXTI_Line14;

EXTI_InitStruct.EXTI_Mode=EXTI_Mode_Interrupt;

EXTI_InitStruct.EXTI_Trigger=EXTI_Trigger_Falling; //下降沿触发中断

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);  

}

void TIM4_Int_Init(u16 arr,u16 psc)

{

  TIM_TimeBaseInitTypeDef  TIM_TimeBaseStructure;

NVIC_InitTypeDef NVIC_InitStructure;

RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM4, ENABLE); //时钟使能

//定时器TIM4初始化

TIM_TimeBaseStructure.TIM_Period = arr; //设置在下一个更新事件装入活动的自动重装载寄存器周期的值

TIM_TimeBaseStructure.TIM_Prescaler =psc; //设置用来作为TIMx时钟频率除数的预分频值

TIM_TimeBaseStructure.TIM_ClockDivision = TIM_CKD_DIV1; //设置时钟分割:TDTS = Tck_tim

TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up;  //TIM向上计数模式

TIM_TimeBaseInit(TIM4, &TIM_TimeBaseStructure); //根据指定的参数初始化TIMx的时间基数单位

TIM_ClearITPendingBit(TIM4, TIM_FLAG_Update);

TIM_ITConfig(TIM4,TIM_IT_Update,ENABLE ); //使能指定的TIM3中断,允许更新中断

//中断优先级NVIC设置

NVIC_InitStructure.NVIC_IRQChannel = TIM4_IRQn;  //TIM4中断

NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 1;  //先占优先级1级

NVIC_InitStructure.NVIC_IRQChannelSubPriority = 1;  //从优先级1级

NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; //IRQ通道被使能

NVIC_Init(&NVIC_InitStructure);  //初始化NVIC寄存器  

}

 int main(void)

 {

NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);//设置中断优先级分组为组2：2位抢占优先级，2位响应优先级

delay_init();

IOConfig();

  TIM4_Int_Init(107, 71); //1M计数频率

  while(1)

{

if(len > 10)

{

len = 0;

USART_Send(USART_buf,11);

}

}

}

void EXTI15_10_IRQHandler(void)

{

if(EXTI_GetFlagStatus(EXTI_Line14) != RESET)

{

if(OI_RXD == 0) 

{

if(recvStat == COM_STOP_BIT)

{

recvStat = COM_START_BIT;

TIM_Cmd(TIM4, ENABLE);

}

}

EXTI_ClearITPendingBit(EXTI_Line14);

}

}

void TIM4_IRQHandler(void)

{  

if(TIM_GetFlagStatus(TIM4, TIM_FLAG_Update) != RESET)

{

TIM_ClearITPendingBit(TIM4, TIM_FLAG_Update);

recvStat++;

if(recvStat == COM_STOP_BIT)

{

TIM_Cmd(TIM4, DISABLE);

USART_buf[len++] = recvData;

return;

}

if(OI_RXD)

{

recvData |= (1 << (recvStat - 1));

}else{

recvData &= ~(1 << (recvStat - 1));

}

  }

}

Demo下载

Demo工程下载地址github。

https://github.com/TonyIOT/SoftWareSerial.git