用stm32f103c8t6的标准库的A11引脚写一个读取dht11传感器的湿度的代码

由于DHT11传感器的数据是通过单总线协议传输的，因此需要先设置GPIO口为输入模式，然后发送起始信号，接收传感器返回的数据，最后计算湿度值。

以下是用stm32f103c8t6的标准库的A11引脚读取dht11传感器湿度的代码：

#include "stm32f10x.h"
#include <stdio.h>

#define DHT11_PIN GPIO_Pin_11
#define DHT11_PORT GPIOA

void delay_us(uint32_t us) {
    uint32_t count = us * (SystemCoreClock / 1000000) / 5;
    while(count--);
}

void DHT11_Start(void) {
    GPIO_InitTypeDef GPIO_InitStructure;

    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOA, ENABLE);

    GPIO_InitStructure.GPIO_Pin = DHT11_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
    GPIO_Init(DHT11_PORT, &GPIO_InitStructure);

    GPIO_SetBits(DHT11_PORT, DHT11_PIN);
    delay_us(1000);
    GPIO_ResetBits(DHT11_PORT, DHT11_PIN);
    delay_us(18000);
    GPIO_SetBits(DHT11_PORT, DHT11_PIN);
    delay_us(20);

    GPIO_InitStructure.GPIO_Pin = DHT11_PIN;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING;
    GPIO_Init(DHT11_PORT, &GPIO_InitStructure);
}

uint8_t DHT11_ReadBit(void) {
    uint8_t retry = 0;
    while (GPIO_ReadInputDataBit(DHT11_PORT, DHT11_PIN) == RESET) {
        if (retry++ > 100) return 0;
        delay_us(1);
    }
    delay_us(40);
    if (GPIO_ReadInputDataBit(DHT11_PORT, DHT11_PIN) == SET) {
        return 1;
    } else {
        return 0;
    }
}

uint8_t DHT11_ReadByte(void) {
    uint8_t i, data = 0;
    for (i = 0; i < 8; i++) {
        data <<= 1;
        data |= DHT11_ReadBit();
    }
    return data;
}

uint8_t DHT11_ReadData(uint8_t *temperature, uint8_t *humidity) {
    uint8_t data[5];
    uint8_t i;

    DHT11_Start();

    if (GPIO_ReadInputDataBit(DHT11_PORT, DHT11_PIN) == RESET) {
        while (GPIO_ReadInputDataBit(DHT11_PORT, DHT11_PIN) == RESET);
        while (GPIO_ReadInputDataBit(DHT11_PORT, DHT11_PIN) == SET);
        for (i = 0; i < 5; i++) {
            data[i] = DHT11_ReadByte();
        }
        if (data[4] == (data[0] + data[1] + data[2] + data[3])) {
            *humidity = data[0];
            *temperature = data[2];
            return 1;
        }
    }
    return 0;
}

int main(void) {
    uint8_t temperature, humidity;

    while(1) {
        if (DHT11_ReadData(&temperature, &humidity) == 1) {
            printf("Temperature: %d*C, Humidity: %d%%\n", temperature, humidity);
        } else {
            printf("Read failed\n");
        }
        delay_us(1000000);
    }
}

注：由于DHT11的数据传输速率很慢，因此在读取数据时需要适当延长延时时间（例如上面的代码中的delay_us函数）。如果延时时间过短，可能会导致读取失败。