HAL库下使用printf

1.包含头文件

#include "stdio.h"

2.重定义串口

int fputc(int ch, FILE *f)
{
 while((USART1->SR & 0X40) == 0); //循环发送,直到发送完毕
 USART1->DR = (uint8_t) ch;
 return ch;
}

3.如果只完成前两步，使用仿真器可以运行，程序自己运行不起来。还需加入以下代码

#pragma import(__use_no_semihosting)
void _sys_exit(int x)
{
    x = x;
}
struct __FILE
{
    int handle;
    /* Whatever you require here. If the only file you are using is */
    /* standard output using printf() for debugging, no file handling */
    /* is required. */
};

FILE __stdout;    /* FILE is typedef’ d in stdio.h. */

经此设置可以避免使用LIB库