STM32F103 USART serial port simple implementation

(Based on the stm32_v5 development board)

1. Create a project and write a C program

#include"stm32f10x.h"

#include"stdarg.h"

void USART1_Config()

{

GPIO_InitTypeDef GPIO_InitStructure;

USART_InitTypeDef USART_InitStructure;

/* Enable USART1 clock */

  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA , ENABLE);

/*Configure USART1 TX and set it to multiplexed push-pull output mode*/

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/*Configure USART1 RX and set it to floating input mode*/

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;

GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;

GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;

GPIO_Init(GPIOA, &GPIO_InitStructure);

/*Configure USART1 mode*/

USART_InitStructure.USART_BaudRate = 57600; //Set the baud rate to 57600//

USART_InitStructure.USART_WordLength = USART_WordLength_8b; //Configure the word length of serial port transmission to 8 bits//

USART_InitStructure.USART_StopBits = USART_StopBits_1; //Configure the stop bit to 1//

USART_InitStructure.USART_Parity = USART_Parity_No; //Do not set the parity bit //

USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; //Do not use hardware flow//

USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx; //Configure the serial port to two-wire full-duplex communication, turn on both RX and Tx modes //

USART_Init(USART1, &USART_InitStructure); //Write configuration parameters to registers//

USART_Cmd(USART1, ENABLE); //Enable USART1 peripheral// 

}

static char *itoa(int value, char *string, int radix)

{

int i, d;

int flag = 0;

char *ptr = string;

/*This implementation only works for decimal numbers*/

if(radix != 10)

{

*ptr = 0;

return string;

  }

if(!value)

{

*ptr++ = 0x30;

*ptr = 0;

return string;

}

/*If this is a negative value, insert a minus sign*/

if(value < 0)

{

*ptr++ = '-';

value *= -1;

}

for(i = 10000; i > 0; i /= 10)

{

d = value / i;

if (d || flag)

{

*ptr++ = (char)(d + 0x30);

value -= (d * i);

flag = 1;

}

}

/*NULL terminated string*/

*ptr = 0;

return string;

}

void USART1_printf(USART_TypeDef* USARTx, uint8_t *Data,...)

{

const char *s;

int d;

char buf[16];

va_list ap;

va_start(ap, Data);

while (*Data != 0) //Judge whether the string terminator has been reached//

{

if(*Data == 0x5c)                                   //'\'//

{

switch( *++Data )

{

case 'r': //Carriage return character//

USART_SendData(USARTx, 0x0d);

Data ++;

break;

case 'n': //line break//

USART_SendData(USARTx, 0x0a);

Data ++;

break;

default:

Data ++;

break;

}

}

else if (*Data == '%')

{

switch (*++Data)

{

case 's': // string //

s = va_arg(ap, const char *);

for(;*s; s++)

{

USART_SendData(USARTx, *s);

while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );

}

Data++;

break;

case 'd': //decimal//

d = va_arg(ap, int);

drown(d, buf , 10);

for(s = buf;*s;s++)

{

USART_SendData(USARTx, *s);

while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );

}

Data++;

break;

default:

Data++;

break;

}

}

else USART_SendData(USARTx, *Data++);

while( USART_GetFlagStatus(USARTx, USART_FLAG_TC) == RESET );

}

}

int main(void)

{

/*Initialize the serial port*/

USART1_Config();

USART1_printf(USART1,"\r\nHello Word\r\n");

while(1);

}

2. Connect J-Link, compile, and download the program into the stm32 development board

3. Connect the serial port and open the serial port debugging assistant for debugging

See Hello World printed, the goal is completed