如何实现安卓app通过蓝牙控制stm32的GPIO实现led灯的亮灭，请呈现相关C语言代码

以下是实现安卓app通过蓝牙控制stm32的GPIO实现led灯的亮灭的C语言代码：

#include "stm32f10x.h"
#include "stm32f10x_gpio.h"
#include "stm32f10x_rcc.h"
#include "stm32f10x_usart.h"

GPIO_InitTypeDef GPIO_InitStructure;
USART_InitTypeDef USART_InitStructure;

void GPIO_Configuration(void) {
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_13;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
  GPIO_Init(GPIOC, &GPIO_InitStructure);
}

void USART_Configuration(void) {
  RCC_APB2PeriphClockCmd(RCC_APB2Periph_USART1 | RCC_APB2Periph_GPIOA, ENABLE);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_9;
  GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  GPIO_InitStructure.GPIO_Pin = GPIO_Pin_10;
  GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
  GPIO_Init(GPIOA, &GPIO_InitStructure);

  USART_InitStructure.USART_BaudRate = 9600;
  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(USART1, &USART_InitStructure);

  USART_Cmd(USART1, ENABLE);
}

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

int main(void) {
  GPIO_Configuration();
  USART_Configuration();

  while (1) {
    char data = USART_ReceiveData(USART1);

    switch (data) {
      case '1':
        GPIO_SetBits(GPIOC, GPIO_Pin_13);
        USART_SendString(USART1, "LED ON\r\n");
        break;
      case '0':
        GPIO_ResetBits(GPIOC, GPIO_Pin_13);
        USART_SendString(USART1, "LED OFF\r\n");
        break;
      default:
        break;
    }
  }
}

该代码使用了STM32的USART串口通信功能，通过蓝牙模块与安卓app进行通信，实现了对LED灯的控制。当接收到字符'1'时，GPIO口输出高电平，LED灯亮起；当接收到字符'0'时，GPIO口输出低电平，LED灯熄灭。同时，通过串口向安卓app发送反馈信息，告知LED灯的状态。