【stm32f103】USART TX发送实现（寄存器版）

本讲主要实现usart TX的实现，主要分几部分的应用

1.      USART 1 Tx polling的实现（附带printf的实现）

2.      USART1 Tx DMA的实现

3.      USART1 TX DMA中断的实现

话不多说，开始

一．硬件原理图

USART1在APB2总线上

二．寄存器图

寄存器可以参考  参考手册，在这里不做详细讨论

三．具体实现

1.      USART 1 Tx polling的实现（附带printf的实现）

1）  编程步骤：

->使能PA9的时钟

->使能USART1的时钟

->配置PA9为推挽复用输出

->配置USART1的波特率为115200（因为USART1在APB2上，计算方法为APB2 clock/波特率）

->使能USART1和TX和USART1

->Polling方式往USART1的DR寄存器填数据

->printf需要重定向fputc

2）  程序调试

->程序调用

USART1_Init();
USART1_TX_Polling(100);

->使能PA9,USART1的时钟

/* 1.ENABLE USART1 GPIOA CLOCK */
RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;
/* 2. ENABLE USART1 IN APB2 BUS CLOCK */
RCC->APB2ENR |=RCC_APB2ENR_USART1EN;

->配置PA9为推挽复用输出

/* 3.CONFIG GPIOA PA9 AF MODE */
GPIOA->CRH &= ~(GPIO_CRH_MODE9 |GPIO_CRH_CNF9);
GPIOA->CRH |=GPIO_CRH_MODE9 | GPIO_CRH_CNF9_1;

此处需要注意一个特别重要的细节：因为CRH默认的value是：

所以如果没有清除到bit4-bit7，直接进行或运算就会造成错误，成为开漏模式，CRL寄存器同样道理，正常运行如图：

->配置波特率为115200

USART1->BRR |= 0x271;

运行效果图

->使能USART1和USART1 TX

USART1->CR1 |= USART_CR1_UE | USART_CR1_TE |USART_CR1_RE;

-> Polling方式往USART1的DR寄存器填数据

voidUSART1_TX_Polling(int loop_cnt)
{
    int index = 0;
    for(;index < loop_cnt;index++)
    {
        while ((USART1->SR &USART_SR_TXE) == 0);
        USART1->DR= 'a';            
    }
    while(1);
}

运行图

->printf fputc重定向

int fputc(int ch, FILE *fp)
{
    if (fp == stdout)
    {
        if (ch == '\n')
        {
            while((USART1->SR & USART_SR_TXE) == 0);
            USART1->DR ='\r';
        }
        while ((USART1->SR &USART_SR_TXE) == 0);
        USART1->DR = ch;
    }
    return ch;
}

2.      USART1 Tx DMA的实现

1）  编程步骤

->使能PA9的时钟

->使能USART1的时钟

->配置PA9为推挽复用输出

->配置USART1的波特率为115200（因为USART1在APB2上，计算方法为APB2 clock/波特率）

->使能USART1和TX和USART1

->设置DMA，请参照DMA文章：

http://blog.csdn.net/xiaoxiaopengbo/article/details/77434744

程序源码

unsigned char buffer[52] = "DMA DATA TEST";
void USART1_TX_DMA()
{
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
    USART1->CR3 |= USART_CR3_DMAT;
    
    /* 6. CONFIG DMA */
    DMA1_Channel4->CMAR = (uint32_t)buffer;
    DMA1_Channel4->CPAR =(uint32_t)&USART1->DR;
    DMA1_Channel4->CNDTR = strlen(buffer);
    DMA1_Channel4->CCR |= DMA_CCR4_PL |DMA_CCR4_DIR | DMA_CCR4_MINC | DMA_CCR4_EN;
    
    while ((DMA1->ISR & DMA_ISR_TCIF4) ==0);
    DMA1->IFCR = DMA_IFCR_CTCIF4;
    DMA1_Channel4->CCR &= ~DMA_CCR4_EN;
    
    while(1);
}

程序调试图：

3.      USART1 TX DMA中断的实现

1）  编程步骤

->设置USART1

->设置DMA以及NVIC中断

->编写DMA中断函数

2）  程序源码

void USART1_TX_DMA_IRPT()
{
    NVIC_SetPriorityGrouping(4);
    
    NVIC_SetPriority(DMA1_Channel4_IRQn, 1);
    
    
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
    USART1->CR3 |= USART_CR3_DMAT;
    
    /* 6. CONFIG DMA */
    DMA1_Channel4->CMAR = (uint32_t)buffer;
    DMA1_Channel4->CPAR =(uint32_t)&USART1->DR;
    DMA1_Channel4->CNDTR = strlen(buffer);
    DMA1_Channel4->CCR |= DMA_CCR4_PL |DMA_CCR4_TCIE | DMA_CCR5_HTIE | DMA_CCR4_DIR | DMA_CCR4_MINC | DMA_CCR4_EN;
    NVIC_EnableIRQ(DMA1_Channel4_IRQn);
    
    while ((DMA1->ISR & DMA_ISR_TCIF4) ==0);
    DMA1->IFCR = DMA_IFCR_CTCIF4;
    DMA1_Channel4->CCR &= ~DMA_CCR4_EN;
    
    
    while(1);
}

3）  程序调试

四. 整个程序源码

#include 
#include 
 
unsigned char buffer[52] = "DMA DATA TEST";
void USART1_Init()
{
    /* 1. ENABLE USART1 GPIOA CLOCK */
    RCC->APB2ENR |= RCC_APB2ENR_IOPAEN;
    /* 2. ENABLE USART1 IN APB2 BUS CLOCK */
    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
    /* 3. CONFIG GPIOA PA9 AF MODE */
    GPIOA->CRH &= ~(GPIO_CRH_MODE9 |GPIO_CRH_CNF9);
    GPIOA->CRH |= GPIO_CRH_MODE9 |GPIO_CRH_CNF9_1;
    
    GPIOA->CRH &= ~(GPIO_CRH_MODE10 |GPIO_CRH_CNF10);
    GPIOA->CRH |= GPIO_CRH_CNF10_1;
    /* 4. CONFIG USART1 BAUD RATE 115200 */
    USART1->BRR |= 0x271;
    /* 5. ENBALE TRANSPORT AND ENABLE USART1 */
    USART1->CR1 |= USART_CR1_UE |USART_CR1_TE | USART_CR1_RE;
    
}
 
void USART1_TX_Polling(int loop_cnt)
{
    int index = 0;
    for(;index < loop_cnt;index++)
    {
             while ((USART1->SR &USART_SR_TXE) == 0);
             USART1->DR = 'a';            
    }
    while(1);
}
 
void USART1_TX_DMA()
{
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
    USART1->CR3 |= USART_CR3_DMAT;
    
    /* 6. CONFIG DMA */
    DMA1_Channel4->CMAR = (uint32_t)buffer;
    DMA1_Channel4->CPAR =(uint32_t)&USART1->DR;
    DMA1_Channel4->CNDTR = strlen(buffer);
    DMA1_Channel4->CCR |= DMA_CCR4_PL |DMA_CCR4_DIR | DMA_CCR4_MINC | DMA_CCR4_EN;
    
    while ((DMA1->ISR & DMA_ISR_TCIF4) ==0);
    DMA1->IFCR = DMA_IFCR_CTCIF4;
    DMA1_Channel4->CCR &= ~DMA_CCR4_EN;
    
    while(1);
}
 
void DMA1_Channel4_IRQHandler(void)
{
    
    if (DMA1->ISR & DMA_ISR_HTIF4)
    {
             DMA1->IFCR = DMA_IFCR_CHTIF4;
             //printf("HTIF: %d\n",DMA1_Channel4->CNDTR);
    }
    
    if (DMA1->ISR & DMA_ISR_TCIF4)
    {
             DMA1->IFCR = DMA_IFCR_CTCIF4;
             //printf("TCIF: %d\n",DMA1_Channel4->CNDTR);
    }
}
 
void USART1_TX_DMA_IRPT()
{
    NVIC_SetPriorityGrouping(4);
    
    NVIC_SetPriority(DMA1_Channel4_IRQn, 1);
    
    
    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
    USART1->CR3 |= USART_CR3_DMAT;
    
    /* 6. CONFIG DMA */
    DMA1_Channel4->CMAR = (uint32_t)buffer;
    DMA1_Channel4->CPAR =(uint32_t)&USART1->DR;
    DMA1_Channel4->CNDTR = strlen(buffer);
    DMA1_Channel4->CCR |= DMA_CCR4_PL |DMA_CCR4_TCIE | DMA_CCR5_HTIE | DMA_CCR4_DIR | DMA_CCR4_MINC | DMA_CCR4_EN;
    NVIC_EnableIRQ(DMA1_Channel4_IRQn);
    
    while ((DMA1->ISR & DMA_ISR_TCIF4) ==0);
    DMA1->IFCR = DMA_IFCR_CTCIF4;
    DMA1_Channel4->CCR &= ~DMA_CCR4_EN;
    
    
    while(1);
}
 
int fputc(int ch, FILE *fp)
{
    if (fp == stdout)
    {
             if (ch == '\n')
             {
                       while ((USART1->SR& USART_SR_TXE) == 0);
                       USART1->DR = '\r';
             }
             while ((USART1->SR &USART_SR_TXE) == 0);
             USART1->DR = ch;
    }
    return ch;
}
 
 
int main()
{
    USART1_Init();
    
    // USART1_TX_Polling(100);
    // USART1_TX_DMA();
    //USART1_TX_DMA_IRPT();    
    while(1);
    
}