STM32 serial port settings and library function introduction

The general steps of serial port settings can be summarized as follows:
1) Enable serial port clock, enable GPIO clock 
2) Reset serial port
3) Set GPIO port mode
4) Initialize serial port parameters 
5) Enable interrupts and initialize NVIC (only if interrupts need to be enabled)
6) Enable serial port

7) Write an interrupt handling function 

Next, we will briefly introduce these firmware library functions that are directly related to the basic configuration of the serial port. These functions and definitions are mainly distributed in the stm32f10x_usart.h and stm32f10x_usart.c files. 

1. Enable the serial port clock. The serial port is mounted on APB2, so the enabling function is:

RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1)

2. Serial port reset. When an abnormality occurs in a peripheral, the peripheral can be reset by resetting it, and then reconfiguring the peripheral to make it work again. Generally, when the system is just beginning to be configured, the peripheral will be reset first to make it work again. The reset is completed in the function USART_DeInit():

void USART_DeInit(USART_TypeDef* USARTx)

3. Serial port parameter initialization

void USART_Init() function: 

     voidUSART_Init(USART_TypeDef*USARTx,USART_InitTypeDef*USART_InitStruct);

effect:

          Initialize the corresponding serial port according to the specified parameters (baud rate, word length, stop bit, parity, hardware flow control, etc.)

           Mainly used to initialize register BRR and CR1, CR2, CR3 control registers

Example:

         USART_InitTypeDefUSART_InitStructure;  

         USART_InitStructure.USART_BaudRate = 9600; //Baud rate setting;

        USART_InitStructure.USART_WordLength= USART_WordLength_8b; //Word length is 8-bit data format

        USART_InitStructure.USART_StopBits= USART_StopBits_1; //One stop bit

        USART_InitStructure.USART_Parity = USART_Parity_No; //No parity bit

        USART_InitStructure.USART_HardwareFlowControl= USART_HardwareFlowControl_None; //No hardware data flow control

       USART_InitStructure.USART_Mode= USART_Mode_Rx| USART_Mode_Tx; //Transmit and receive mode

      USART_Init(USART1,&USART_InitStructure); //Initialize the serial port

4. void USART_Cmd() function: 

prototype:

      voidUSART_Cmd(USART_TypeDef*USARTx,FunctionalStateNewState);

effect:

            Enable the corresponding serial port, which is used to set the serial port enable bit of register CR1

 Example:

           USART_Cmd(USART1,ENABLE); //Enable serial port 1

5. void USART_ITConfig() function: 

Prototype: voidUSART_ITConfig(USART_TypeDef*USARTx,

   uint16_t USART_IT, FunctionalStateNewState);

 Function: Enable the corresponding interrupt of the serial port and set the serial port control register

  Example:

            USART_ITConfig(USART1,USART_IT_RXNE, ENABLE); //Enable the read data register non-empty interrupt

6.USART_SendData() function: 

prototype:

       voidUSART_SendData(USART_TypeDef* USARTx, uint16_t Data);

  effect:

            Send data to the serial port.

 Example:

          USART_SendData(USART1,0x12);                    

7.uint16_tUSART_ReceiveData() function: 

Prototype: uint16_t USART_ReceiveData(USART_TypeDef*USARTx)

Get the value most recently received by the serial port.

 Example:

     USART_ReceiveData(USART1);

8. Functions related to the four status flags:

FlagStatusUSART_GetFlagStatus(USART_TypeDef*USARTx,uint16_t USART_FLAG);

void USART_ClearFlag(USART_TypeDef*USARTx,uint16_t USART_FLAG);

ITStatusUSART_GetITStatus(USART_TypeDef*USARTx,uint16_t USART_IT);

void USART_ClearITPendingBit(USART_TypeDef*USARTx,uint16_t USART_IT);

The following is a complete initialization serial port function and an interrupt service function:

//Initialize IO serial port 1 
//bound: baud rate
void uart_init(u32 bound){
    //GPIO port settings
    GPIO_InitTypeDef GPIO_InitStructure;
 USART_InitTypeDef USART_InitStructure;
 NVIC_InitTypeDef NVIC_InitStructure;
 
 RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1|RCC_APB2Periph_GPIOA, ENABLE);//Enable USART1, GPIOA clock
   USART_DeInit(USART1); //Reset serial port 1
//USART1_TX PA.9
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9; //PA.9
    GPIO_InitStructure.GPIO_Speed ​​= GPIO_Speed_50MHz;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;//Multiplexed push-pull output
    GPIO_Init(GPIOA, &GPIO_InitStructure); //Initialize PA9
   
    //USART1_RX PA.10
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;//Floating input
    GPIO_Init(GPIOA, &GPIO_InitStructure); //Initialize PA10


   //Usart1 NVIC configuration


    NVIC_InitStructure.NVIC_IRQChannel = USART1_IRQn;
 NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority=3 ;//Preemption priority 3
 NVIC_InitStructure.NVIC_IRQChannelSubPriority = 3;//Sub priority 3
 NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE; // IRQ channel enable
 NVIC_Init(&NVIC_InitStructure); // Initialize VIC registers according to the specified parameters
  
   // USART initialization settings


USART_InitStructure.USART_BaudRate = bound; // Generally set to 9600;
USART_InitStructure.USART_WordLength = USART_WordLength_8b; // Word length is 8-bit data format
USART_InitStructure.USART_StopBits = USART_StopBits_1; // One stop bit
USART_InitStructure.USART_Parity = USART_Parity_No; // No parity bit
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; // No hardware data flow control
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //transmit and receive mode


    USART_Init(USART1, &USART_InitStructure); //initialize the serial port
    USART_ITConfig(USART1, USART_IT_RXNE, ENABLE); //enable interrupt
    USART_Cmd(USART1, ENABLE); //enable the serial port 


}

void USART1_IRQHandler(void) //Serial port 1 interrupt service routine
{
u8 Res;
#ifdef OS_TICKS_PER_SEC //If the clock tick number is defined, it means that ucosII is to be used.
OSIntEnter();    
#endif
if(USART_GetITStatus(USART1, USART_IT_RXNE) != RESET) //Receive interrupt (the received data must end with 0x0d 0x0a)
{
Res =USART_ReceiveData(USART1);//(USART1->DR);//Read received data

if((USART_RX_STA&0x8000)==0)//Reception is not completed
{
if(USART_RX_STA&0x4000)//Received 0x0d
{
if(Res!=0x0a)USART_RX_STA=0;//Reception error, restart
else USART_RX_STA|=0x8000;//Reception is completed 
}
else //Has not received 0X0D yet
{
if(Res==0x0d)USART_RX_STA|=0x4000;
else
{
USART_RX_BUF[USART_RX_STA&0X3FFF]=Res ;
USART_RX_STA++;
if(USART_RX_STA>(USART_REC_LEN-1))USART_RX_STA=0;//Receive data error, restart receiving 
}  
}
}    
     } 

#ifdef OS_TICKS_PER_SEC//If the clock tick number is defined, it means that ucosII is to be used.
OSIntExit();   
#endif
}