基于STM32F103C8T6单片机写一段NEC解码程序，要求通过PB9引脚连接接收端，然后将解出的码通过PB8发送出去

以下是基于STM32F103C8T6单片机的NEC解码程序，需要通过PB9引脚连接接收端，然后将解出的码通过PB8发送出去：

#include "stm32f10x.h"

void IR_Decode_Init(void);
void IR_Decode_GPIO_Config(void);
void IR_Decode_EXTI_Config(void);

void USART1_Config(void);
void USART1_SendChar(uint8_t ch);
void USART1_SendString(uint8_t *str);

uint8_t IR_Received = 0;
uint32_t IR_ReceivedData = 0;

int main(void)
{
    IR_Decode_Init();
    USART1_Config();

    while(1)
    {
        if(IR_Received)
        {
            USART1_SendString("Received NEC Code: ");
            USART1_SendChar((IR_ReceivedData >> 24) & 0xFF);
            USART1_SendChar((IR_ReceivedData >> 16) & 0xFF);
            USART1_SendChar((IR_ReceivedData >> 8) & 0xFF);
            USART1_SendChar(IR_ReceivedData & 0xFF);
            USART1_SendString("\r\n");

            IR_Received = 0;
        }
    }
}

void IR_Decode_Init(void)
{
    IR_Decode_GPIO_Config();
    IR_Decode_EXTI_Config();
}

void IR_Decode_GPIO_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStruct;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_8;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_AF_PP;
    GPIO_InitStruct.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(GPIOB, &GPIO_InitStruct);

    GPIO_InitStruct.GPIO_Pin = GPIO_Pin_9;
    GPIO_InitStruct.GPIO_Mode = GPIO_Mode_IPU;
    GPIO_Init(GPIOB, &GPIO_InitStruct);
}

void IR_Decode_EXTI_Config(void)
{
    EXTI_InitTypeDef EXTI_InitStruct;
    NVIC_InitTypeDef NVIC_InitStruct;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);

    EXTI_InitStruct.EXTI_Line = EXTI_Line9;
    EXTI_InitStruct.EXTI_Mode = EXTI_Mode_Interrupt;
    EXTI_InitStruct.EXTI_Trigger = EXTI_Trigger_Falling;
    EXTI_InitStruct.EXTI_LineCmd = ENABLE;
    EXTI_Init(&EXTI_InitStruct);

    GPIO_EXTILineConfig(GPIO_PortSourceGPIOB, GPIO_PinSource9);

    NVIC_InitStruct.NVIC_IRQChannel = EXTI9_5_IRQn;
    NVIC_InitStruct.NVIC_IRQChannelPreemptionPriority = 0x00;
    NVIC_InitStruct.NVIC_IRQChannelSubPriority = 0x00;
    NVIC_InitStruct.NVIC_IRQChannelCmd = ENABLE;
    NVIC_Init(&NVIC_InitStruct);
}

void EXTI9_5_IRQHandler(void)
{
    if(EXTI_GetITStatus(EXTI_Line9) != RESET)
    {
        static uint32_t IR_LastTime = 0;
        static uint32_t IR_Data = 0;
        static uint8_t IR_BitCount = 0;
        uint32_t IR_CurrentTime = TIM2->CNT;

        if(IR_CurrentTime - IR_LastTime > 4500 && IR_CurrentTime - IR_LastTime < 5000)
        {
            IR_Data = 0;
            IR_BitCount = 0;
        }
        else if(IR_CurrentTime - IR_LastTime > 2250 && IR_CurrentTime - IR_LastTime < 2750)
        {
            IR_Data = (IR_Data << 1) | 0x01;
            IR_BitCount++;

            if(IR_BitCount == 32)
            {
                IR_ReceivedData = IR_Data;
                IR_Received = 1;
            }
        }
        else if(IR_CurrentTime - IR_LastTime > 560 && IR_CurrentTime - IR_LastTime < 680)
        {
            IR_Data = (IR_Data << 1) & 0xFFFFFFFE;
            IR_BitCount++;

            if(IR_BitCount == 32)
            {
                IR_ReceivedData = IR_Data;
                IR_Received = 1;
            }
        }

        IR_LastTime = IR_CurrentTime;

        EXTI_ClearITPendingBit(EXTI_Line9);
    }
}

void USART1_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStruct;
    USART_InitTypeDef USART_InitStruct;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA | RCC_APB2Periph_USART1, ENABLE);

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

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

    USART_InitStruct.USART_BaudRate = 115200;
    USART_InitStruct.USART_WordLength = USART_WordLength_8b;
    USART_InitStruct.USART_StopBits = USART_StopBits_1;
    USART_InitStruct.USART_Parity = USART_Parity_No;
    USART_InitStruct.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
    USART_InitStruct.USART_Mode = USART_Mode_Tx;
    USART_Init(USART1, &USART_InitStruct);

    USART_Cmd(USART1, ENABLE);
}

void USART1_SendChar(uint8_t ch)
{
    while(USART_GetFlagStatus(USART1, USART_FLAG_TXE) == RESET);
    USART_SendData(USART1, ch);
}

void USART1_SendString(uint8_t *str)
{
    while(*str)
    {
        USART1_SendChar(*str++);
    }
}

这段程序的实现过程是：首先通过PB9引脚连接一个红外接收头，然后当接收到红外信号时，通过EXTI中断进行解码，将解出的码存储在IR_ReceivedData变量中。程序通过USART1串口将解码出的码发送出去，使用PB8引脚连接一个红外发射器即可实现发送功能。