c - 嵌入DHT11，第一次打印后温度变为0

Question

所以，我正在尝试在C环境中设置DHT11来尝试学习一些更多的嵌入式软件编程。

我从 other sources 获得了帮助和 documentation创建此温度，温度仅显示一次，然后默认为 0。

我使用 Arduino 作为微 Controller (因为它是我唯一的微 Controller )，并使用 Linux Ubuntu 环境将程序加载到微 Controller 中。

最后，代码如下:

#include <avr/io.h>
#include <stdio.h>
#include <stdlib.h>
#include <util/delay.h>

#include "dht.h"

// Trying to set up the DHT11 so it can be used in this project
void read() {

  // The bits are for to get the temperature values in.
  // reqCounter is for the request later on.
  uint8_t bits[5];

  // Setting up the DDRD as OUTPUT and PORTD as HIGH
  DDRD |= (1 << DDD5);
  PORTD |= (1 << PORTD5);
  _delay_ms(100);

  /*
   * Makes an request to get the data from the DHT11
   * Set the the PORTD5 as LOW
  */
  PORTD &= ~(1 << PORTD5);
  _delay_ms(18);
  // Setting it back to high and DDRD as an input
  PORTD |= (1 << PORTD5);
  _delay_us(1);
  DDRD &= ~(1 << DDD5);

  /*
   * Checking to see if the ACK is happening
  */
  _delay_us(39);
  if ((PIND & (1 << PIND5))) {
    return;
  }
  _delay_us(80);
  if (!(PIND & (1 << PIND5))) {
    return;
  }
  _delay_us(80);

  // Holds the temperature 
  uint8_t temp;

  // Reading the data
  for (uint8_t i = 0; i < 5; i++) {
    // Create a for loop that looks in to every 8 bits
    for (uint8_t j = 0; j < 8; j++) {
      // While it isn`t high, loop this while loop
      while (!(PIND & (1 << PIND5)))
              ;
        _delay_us(30);
        // Looking if the input is still high after 30us
        if (PIND & (1 << PIND5)) {
          temp |= (1 << (7-i));
        }
        // Wait until the input is low.
        while (PIND & (1 << PIND5))
          ;
    }
      // Put the temperature in the bit array
      bits[i] = temp;
  }

  // Resets the pins
  DDRD |= (1 << DDD5);
  PORTD |= (1 << PORTD5);
  _delay_ms(100);

  uint8_t temperature ;
  //checks the sum and gets the temperature 
  if (bits[0] + bits[1] + bits[2] + bits[3] == bits[4]) {
    temperature = bits[2];
  }

  printf("temperature : %d\n", temperature );
  /*printf("%d", bits[0]);
  printf("%d", bits[1]);
  printf("%d", bits[2]);
  printf("%d", bits[3]);
  printf("%d\n", bits[4]);*/
}

这只会产生 15 次，然后记录更多。我尝试对它吹气以提高温度，但没有任何反应。

这里可能存在什么问题？

提前致谢

Answer 1

这里:

  uint8_t temperature ;
  //checks the sum and gets the temperature 
  if (bits[0] + bits[1] + bits[2] + bits[3] == bits[4]) {
    temperature = bits[2];
  }

  printf("temperature : %d\n", temperature );

如果bits[0]+bits[1]+bits[2]+bits[3]==bits[4]为false，则温度被初始化(并且可以有任何值 - 包括零或 15，其中一个值是垃圾)。

也许:

static uint8_t temperature = 0 ;

因此，当bits[0]+bits[1]+bits[2]+bits[3]!=bits[4]时，将使用最后的有效温度。

或者更简单地说，如果温度不在其他地方使用:

  //checks the sum and gets the temperature 
  if (bits[0] + bits[1] + bits[2] + bits[3] == bits[4]) 
  {
      printf( "temperature : %d\n", bits[2] ) ;
  }

我想象这里发生的是温度的未初始化值恰好是15并且你打印它，然后bits[0]+bits[1]+bits[2 ] + 位[3] == 位[4] 变为true 并且位[2] 始终为零。在这种情况下，错误出现在输入和放置在 bits[] 中的值中，此解决方案将导致值始终为零。