MiniSTM32板子上面的串口问题

liklon

下面一段串口初始化USART1能够重映像到PB6和PB7脚。我写的程序总是不行。不重映像可以。

void UART1Config(uint8 SystemClock,uint16 baudrate)

{

double Num;

uint16 Mantissa;

uint8 Fraction;

RCC->APB2RSTR |= 1 << 14;

RCC->APB2RSTR &= ~(1 << 14);   //复位

RCC->APB2ENR |= 1 << 14;  //UART1时钟使能

RCC->APB2ENR |= 0X01;    //辅助功能时钟使能

RCC->APB2ENR |= 1 << 3; //PB口时钟开启

AFIO->MAPR |= 1 << 2;     //UART1的重映射TX/PB6,RX/PB7

GPIOB->CRL &= 0X00FFFFFF;

GPIOB->CRL |= 0X8B000000; //TX为复用功能推挽输出，RX为上拉输入

GPIOB->ODR |= 1 << 7;     //上拉

Num = (double)(SystemClock * 1000000) / baudrate  / 16; //算出DIV_Mantissa和DIV_Fraction

Mantissa = (uint16)Num;

Fraction = (uint8)((Num - Mantissa) * 16);

USART1->BRR = ((Mantissa << 4) + Fraction);

USART1->CR1 &= ~(1 << 12);  //一个起始位，8个数据位，n个停止位

USART1->CR1 |= 1 << 5;      //收到数据产生中断

USART1->CR1 |= 1 << 3;   //发送使能

USART1->CR1 |= 1 << 2;   //接收使能

USART1->CR1 |= 1 << 13;   //串口使能

NVIC_Config(3,3,USART1_IRQChannel,2);  

}

看看哪里有问题啊