STM32-Serial Port Program

    When learning about various hardware, the serial port is an essential and first peripheral to learn, because with the serial port, you can interact with the hardware in a simple way, and it is also easier to verify the correctness of the written program. 
   STM32 has multiple USARTs and supports multiple modes of configuration. For details, please refer to the relevant manual of STM32 for learning.

Let's take a look at the functional block diagram of USART: 

Before using any peripheral function, you should look at its corresponding functional block diagram, which will help you understand the use of the function. 
Next, take a look at the relevant registers and operable library functions of USART. 

Finally, we need to look at the pin multiplexing of GPIO and USART: 

Because USART communicates with the outside world using the multiplexing function of the controller's GPIO pins, you need to configure GPIO to the corresponding input and output mode before using the USART function. 
At the same time, if you need to enable interrupts, you also need to enable the interrupt channel and set the priority grouping.

#include "stm32f10x.h"

/**

  * @brief Initialize GPIO, the default speed is GPIO_Speed_50MHz;

  *         

  * @param GPIO group

  * @param GPIO pin

    * @param GPIO pin mode

  * @retval None

  */

void GPIO_init(GPIO_TypeDef * GPIOx,u16 GPIO_Pin,GPIOMode_TypeDef Mode)

{

    GPIO_InitTypeDef GPIO_InitStruct;                                       

    GPIO_InitStruct.GPIO_Mode=Mode;                         

    GPIO_InitStruct.GPIO_Pin=GPIO_Pin;

    GPIO_InitStruct.GPIO_Speed=GPIO_Speed_50MHz;

    GPIO_Init(GPIOx,&GPIO_InitStruct);

}

/**

  * @brief Initialize USART

  *         

  * @param baud rate, number of data bits, stop bits, send/receive mode

  * @retval None

  */

void UART_init(int BaudRate,u16 WordLength,u16 StopBits,u16 Parity,u16 Mode)

{

    USART_InitTypeDef USART_InitStruct;

    USART_InitStruct.USART_BaudRate=BaudRate;

    USART_InitStruct.USART_HardwareFlowControl=USART_HardwareFlowControl_None;

    USART_InitStruct.USART_Mode=Mode;   

    USART_InitStruct.USART_Parity=Parity;

    USART_InitStruct.USART_StopBits=StopBits;

    USART_InitStruct.USART_WordLength=WordLength;

    USART_Init(USART1,&USART_InitStruct);

    USART_ITConfig(USART1,USART_IT_RXNE,ENABLE);

    USART_Cmd(USART1,ENABLE);

}

/**

  * @brief Initialize interrupt vector

  *         

  * @param interrupt channel, preemption priority, corresponding priority, enable/disable

  * @retval None

  */

void NVIC_init(u8 NVIC_IRQChannel,u8 NVIC_IRQChannelPreemptionPriority,u8 NVIC_IRQChannelSubPriority,u8 NVIC_IRQChannelCmd)

{

        NVIC_InitTypeDef NVIC_InitStrue;

        NVIC_InitStrue.NVIC_IRQChannel=NVIC_IRQChannel;

        NVIC_InitStrue.NVIC_IRQChannelCmd=NVIC_IRQChannelCmd;

        NVIC_InitStrue.NVIC_IRQChannelPreemptionPriority=NVIC_IRQChannelPreemptionPriority;

        NVIC_InitStrue.NVIC_IRQChannelSubPriority=NVIC_IRQChannelSubPriority;

        NVIC_Init(&NVIC_InitStrue);

}

int main()

{

        RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA,ENABLE);

        RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1,ENABLE);

        NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);

        GPIO_init(GPIOA,GPIO_Pin_9,GPIO_Mode_AF_PP);

        GPIO_init(GPIOA,GPIO_Pin_10,GPIO_Mode_IN_FLOATING);

        NVIC_init(USART1_IRQn,1,1,ENABLE);

        GPIO_init(GPIOA,GPIO_Pin_0,GPIO_Mode_Out_PP);

        GPIO_ResetBits(GPIOA,GPIO_Pin_0);

        UART_init(115200,USART_WordLength_8b,USART_StopBits_1,USART_Parity_No,USART_Mode_Tx|USART_Mode_Rx);

        while(1);

}

void USART1_IRQHandler(void)

{

    u8 res;

    if(USART_GetITStatus(USART1,USART_IT_RXNE))

    {

        res=USART_ReceiveData(USART1);

        USART_SendData(USART1,res);

    }

}

The last function is the response function of the serial port receive interrupt. When the serial port receives data and the response flag is set to 1, it enters the interrupt function, provided that the serial port receive interrupt is enabled. 

   The above program realizes the reception and transmission of the serial port, sending and receiving the incoming data.