STM32F103ZE单片机利用按键控制串口一给PC端发送字符串，请从头文件开始详细描述

好的，我会从头文件开始详细描述如何利用按键控制串口一给PC端发送字符串。

1. 首先需要包含以下头文件：

#include "stm32f10x.h"
#include "stm32f10x_usart.h"
#include "stm32f10x_gpio.h"

2. 定义串口和GPIO的引脚：

#define USARTy                   USART1
#define USARTy_GPIO              GPIOA
#define USARTy_CLK               RCC_APB2Periph_USART1
#define USARTy_GPIO_CLK          RCC_APB2Periph_GPIOA
#define USARTy_RxPin             GPIO_Pin_10
#define USARTy_TxPin             GPIO_Pin_9
#define USARTy_IRQn              USART1_IRQn

3. 初始化串口和GPIO的引脚：

GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;

// 使能GPIO和USART的时钟
RCC_APB2PeriphClockCmd(USARTy_GPIO_CLK | USARTy_CLK, ENABLE);

// 配置USART引脚
GPIO_InitStructure.GPIO_Pin = USARTy_TxPin;
GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
GPIO_Init(USARTy_GPIO, &GPIO_InitStructure);

GPIO_InitStructure.GPIO_Pin = USARTy_RxPin;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
GPIO_Init(USARTy_GPIO, &GPIO_InitStructure);

// 配置USART
USART_InitStructure.USART_BaudRate = 115200;
USART_InitStructure.USART_WordLength = USART_WordLength_8b;
USART_InitStructure.USART_StopBits = USART_StopBits_1;
USART_InitStructure.USART_Parity = USART_Parity_No;
USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
USART_InitStructure.USART_Mode = USART_Mode_Rx | USART_Mode_Tx;
USART_Init(USARTy, &USART_InitStructure);

// 使能USART
USART_Cmd(USARTy, ENABLE);

4. 初始化外部中断引脚（按键）：

GPIO_InitStructure.GPIO_Pin = GPIO_Pin_0;
GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU;
GPIO_Init(GPIOA, &GPIO_InitStructure);

// 配置外部中断
EXTI_InitTypeDef EXTI_InitStructure;
NVIC_InitTypeDef NVIC_InitStructure;

// 使能AFIO时钟
RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

// 配置外部中断线路
GPIO_EXTILineConfig(GPIO_PortSourceGPIOA, GPIO_PinSource0);

// 配置外部中断
EXTI_InitStructure.EXTI_Line = EXTI_Line0;
EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Falling;
EXTI_InitStructure.EXTI_LineCmd = ENABLE;
EXTI_Init(&EXTI_InitStructure);

// 配置NVIC
NVIC_InitStructure.NVIC_IRQChannel = EXTI0_IRQn;
NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x00;
NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x00;
NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
NVIC_Init(&NVIC_InitStructure);

5. 在`EXTI0_IRQHandler()`中处理按键按下事件：

void EXTI0_IRQHandler(void)
{
  if(EXTI_GetITStatus(EXTI_Line0) != RESET)
  {
    // 发送字符串
    USART_SendString(USART1, "Hello World!\r\n");
    
    EXTI_ClearITPendingBit(EXTI_Line0);
  }
}

6. 最后，定义一个`USART_SendString()`函数来发送字符串：

void USART_SendString(USART_TypeDef* USARTx, char* str)
{
  while(*str)
  {
    while(USART_GetFlagStatus(USARTx, USART_FLAG_TXE) == RESET);
    USART_SendData(USARTx, *str++);
  }
}

这样就完成了利用按键控制串口一给PC端发送字符串的代码实现。