在Keil环境下使用JLink实现printf输出重定向至debug窗口

在工程里面添加下列代码：

#include <stdio.h>

#define ITM_Port8(n)    (*((volatile unsigned char *)(0xE0000000+4*n)))
#define ITM_Port16(n)   (*((volatile unsigned short*)(0xE0000000+4*n)))
#define ITM_Port32(n)   (*((volatile unsigned long *)(0xE0000000+4*n)))
#define DEMCR           (*((volatile unsigned long *)(0xE000EDFC)))
#define TRCENA          0x01000000

//半主机模式必须定义这个
struct __FILE
{
int handle;
};
FILE __stdout;
FILE __stdin;

int fputc(int ch, FILE *f)
{
if (DEMCR & TRCENA)
{
while (ITM_Port32(0) == 0);

ITM_Port8(0) = ch;
}
return(ch);
}