（学习经验）如何从头文件开始设置STM32串口通讯

只看该作者 · 2023-12-20 11:12

运用STM32的库函数时，有时候为了看懂一句语句需要翻遍整个头文件，找到头文件中预定义的名字到底代表的是什么意思，具体寄存器设置的数值是多少，相当麻烦。我花了一天的时间才明白串口设置的具体过程，只是库函数想的比较周全。下面是我调试好的串口设置程序，头文件是我自己定义的，舍去了库文件中繁琐的结构体定义…… 首先定义头文件：

//*********************控制时钟的一些寄存器*********************

//RCC-Register

//

#define RCC_CR       (*((volatile unsigned long *)0x40021000))

#define RCC_CFGR    (*((volatile unsigned long *)0x40021004))

#define RCC_CIR    (*((volatile unsigned long *)0x40021008))

#define RCC_APB2RSTR  (*((volatile unsigned long *)0x4002100C))

#define RCC_APB1RSTR  (*((volatile unsigned long *)0x40021010))

#define RCC_AHBENR (*((volatile unsigned long *)0x40021014))

#define RCC_APB2ENR (*((volatile unsigned long *)0x40021018))

#define RCC_APB1ENR (*((volatile unsigned long *)0x4002101C))

#define RCC_BDCR    (*((volatile unsigned long *)0x40021020))

#define RCC_CSR    (*((volatile unsigned long *)0x40021024))

//*****************************************************************************

// 端口A，串口1要用到PORTA 9.10两个引脚

// General-Purpose Input/Outputs (PORTA)

//

//*****************************************************************************

#define GPIO_PORTA    ((volatile unsigned long *)0x40010800)

#define GPIO_PORTA_CRL (*((volatile unsigned long *)0x40010800))

#define GPIO_PORTA_CRH (*((volatile unsigned long *)0x40010804))

#define GPIO_PORTA_IDR (*((volatile unsigned long *)0x40010808))

#define GPIO_PORTA_ODR (*((volatile unsigned long *)0x4001080C))

#define GPIO_PORTA_BSRR  (*((volatile unsigned long *)0x40010810))

#define GPIO_PORTA_BRR (*((volatile unsigned long *)0x40010814))

#define GPIO_PORTA_LCKR  (*((volatile unsigned long *)0x40010818))

//*****************************************************************************

// 串口1寄存器

// USART1-Register

//

//*****************************************************************************

#define USART1_SR (*((volatile unsigned long *)0x40013800))

#define USART1_DR (*((volatile unsigned long *)0x40013804))

#define USART1_BRR (*((volatile unsigned long *)0x40013808))

#define USART1_CR1 (*((volatile unsigned long *)0x4001380C))

#define USART1_CR2 (*((volatile unsigned long *)0x40013810))

#define USART1_CR3 (*((volatile unsigned long *)0x40013814))

#define USART1_GTPR  (*((volatile unsigned long *)0x40013818))
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要进行串口通讯，首先要设置时钟，时钟源是什么?PLL还是HSE还是HIS？时钟分频是多少？这些都要设置，不然没法计算波特率，波特率的公式在这就不详细列出了下面是系统初始化，也就是初始化系统时钟：

void SystemInit0 (void)

{

unsigned long StartUpCounter = 0, HSEStatus = 0;

   RCC_CR |=0x00000001; ///*!< Set HSION bit */

/*!< Reset SW[1:0], HPRE[3:0], PPRE1[2:0], PPRE2[2:0], ADCPRE[1:0] and MCO[2:0] bits */

  RCC_CFGR &= (uint32_t)0xF8FF0000;

  RCC_CR &= (uint32_t)0xFEF6FFFF; // /*!< Reset HSEON, CSSON and PLLON bits */

RCC_CR &= (uint32_t)0xFFFBFFFF; ///*!< Reset HSEBYP bit */

  RCC_CFGR &= (uint32_t)0xFF80FFFF; ///*!< Reset PLLSRC, PLLXTPRE, PLLMUL[3:0] and USBPRE bits */

RCC_CIR = 0x00000000;//*!< Disable all interrupts */

/*!< SYSCLK, HCLK, PCLK2 and PCLK1 configuration ---------------------------*/

  RCC_CR |=0x00010000; // /*!< Enable HSE */

  /*!< Wait till HSE is ready and if Time out is reached exit */

  do

  {

HSEStatus = RCC_CR & 0x00020000;

StartUpCounter++;

  } while((HSEStatus == 0) && (StartUpCounter != 0x0500));

  if ((RCC_CR & 0x00020000) != 0)

  {

HSEStatus =0x01;

  }

  else

  {

HSEStatus =0x00;

  }

  if (HSEStatus ==0x01)

  {

RCC_CFGR |=0x00000000; ///*!< HCLK = SYSCLK */

   RCC_CFGR |=0x00000000; ///*!< PCLK2 = HCLK */

   RCC_CFGR |=0x00000000; ///*!< PCLK1 = HCLK */

RCC_CFGR &=(~(0x00010000 | 0x00020000 | 0x003C0000));

RCC_CFGR |= 0x00010000 | 0x00020000 | 0x000C0000;///*!< PLLCLK = (8MHz / 2) * 5 = 20 MHz */

   RCC_CR |= 0x01000000;// /*!< Enable PLL */

      while((RCC_CR & 0x02000000) == 0) // /*!< Wait till PLL is ready */

      {

      }

RCC_CFGR &=~0x00000003;

RCC_CFGR |=0x00000002; ///*!< Select PLL as system clock source */

   while ((RCC_CFGR &0x0000000C) !=0x08)  ///*!< Wait till PLL is used as system clock source */

{

}

  }

  else

  { while (1)

   {

   }

  }

}

设置好时钟就可以串口初始化了:

void stm32_UsartSetup () //串口初始化

{

RCC_APB2ENR|=0x00004000; // enable clock for USART1

RCC_APB2ENR|=0x00000001; //复用功能IO时钟使能

RCC_APB2ENR|=0x00000004; //端口A时钟使能

GPIO_PORTA_CRH&=~(0x00000FF0); // Clear PA9, PA10

GPIO_PORTA_CRH|=0x000000B0; // USART1 Tx (PA9)  alternate output push-pull

GPIO_PORTA_CRH|=0x00000400; // USART1 Rx (PA10) input floating

USART1_BRR=0x00000823;  ////波特率9600/20M

USART1_CR1&=0xFFFFEFFF;  // set Data bits

USART1_CR2&=0xFFFFCFFF; // set Stop bits

USART1_CR1&=0xFFFFFBFF;  //  // set Parity

USART1_CR1|=(0x00000004|0x00000008);    // RX, TX enable

USART1_CR1|=0x00002000; // USART enable

}

到此串口设置设置完毕，下面我要和PC机通讯了，我要从上位机通过串口助手发送一字节的十六进制数，然后下位机（STM32）返回给PC机所发的一字节数据：

int main()

{

  SystemInit0();

stm32_UsartSetup ();

while(1)

{

while(USART1->SR&0x00000020)  //等待RXNE置位

{

   flag=USART1_DR&0xff;

  USART1_DR=flag&0xff;

while((USART1->SR)&0x80==0); //等待发送完毕

while((USART1->SR)&0x40==0);

flag=USART1->SR;

  }

}

}
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