.\output\stm32f103.axf: Error: L6218E: Undefined symbol UsartPrintf (referred from stm32f10x_it.o).

根据你提供的引用信息，错误信息".\output\stm32f103.axf: Error: L6218E: Undefined symbol UsartPrintf (referred from stm32f10x_it.o)"指出在stm32f10x_it.o文件中引用了未定义的符号UsartPrintf。解决该问题的方法可以参考之前解决SystemInit未定义的方法类似，即在代码中增加对UsartPrintf的定义。具体做法是在代码中包含头文件"stm32f10x.h"，并在main函数之前声明UsartPrintf函数，如下所示：

#include "stm32f10x.h"
void UsartPrintf(void); //声明UsartPrintf函数

int main(void) {
while(1);
}

void UsartPrintf(void) {
//UsartPrintf函数的具体实现
}

这样，在编译时就能正确找到和解析UsartPrintf函数的定义，从而解决该错误。请注意，具体的UsartPrintf函数的实现需要根据你的具体需求进行编写。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
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