Comcat：以“以 DHT21/AM2301 数字温湿度传感器为例，示例如下 Arduino 封装的库都在 /PATH/TO/Arduino-1.0.1/libraries 下，因此我们自己写的库也...”为内容创建页面

2014-06-25T09:05:01Z

以“以 DHT21/AM2301 数字温湿度传感器为例，示例如下 Arduino 封装的库都在 /PATH/TO/Arduino-1.0.1/libraries 下，因此我们自己写的库也...”为内容创建页面

新页面

以 [[DHT21/AM2301 数字温湿度传感器]] 为例，示例如下

Arduino 封装的库都在 /PATH/TO/Arduino-1.0.1/libraries 下，因此我们自己写的库也要放在这个目录下

在 /PATH/TO/Arduino-1.0.1/libraries 下建立 DH21 这个目录，把 dh21.h dh21.cpp 这两个文件置于其中即可使用（由此可见 Arduino 的库创建和使用都很方便），重启 Arduino 开发环境后，可在 Sketch –> Import Library 下看到 DH21

使用示例如下：

<source lang="c">
#include <dh21.h>

/* the data line of DH21 is pluged in digital pin #12 */
DH21 dh21(12);

void setup()
{
Serial.begin(9600);
}

void loop()
{
if(dh21.get_data() == -1)
Serial.println("Read DH21 error");
else
{
Serial.print("Temperature: ");
Serial.print(dh21.temperature());
Serial.print("C ");
Serial.print("Humidity: ");
Serial.print(dh21.humidity());
Serial.println("%");
}

/* read after 5 seconds */
delay(5000);
}
</source>

运行界面：

[[文件:create-arduino-dh21-lib.png]]

'''dh21.h'''

<source lang="c">
/*
* dh21.h - Library for DH21/AM2301 digital temperature sensor
* Created by Jack Tan <jiankemeng@gmail.com>
* Released into the public domain.
*/
#ifndef _DH21_H_
#define _DH21_H_

#include <Arduino.h>

class DH21
{
public:
DH21(int pin);
float temperature();
float humidity();
char get_data();
char data_check();

private:
char read_8bits();
int pin;
char RH_H;
char RH_L;
char T_H;
char T_L;
char crc;
};

#endif
</source>

'''dh21.cpp'''

<source lang="c">
/*
* dh21.cpp - Library for DH21/AM2301 digital temperature sensor
* Created by Jack Tan <jiankemeng@gmail.com>
* Released into the public domain.
*/

#include "dh21.h"

DH21::DH21(int p)
{
pin = p;
pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH);
}

char DH21::get_data()
{
char flag;
pinMode(pin, OUTPUT);

/* Bus Low, delay 1 - 5ms */
digitalWrite(pin, LOW);
delay(4);

/* Bus High, delay 40us */
digitalWrite(pin, HIGH);
delayMicroseconds(40);

pinMode(pin, INPUT);
if(digitalRead(pin) == 0)
{
flag = 2;
/* waitting the ACK signal (Low, 80us) */
while((digitalRead(pin) == 0) && flag++);
flag = 2;
/* waitting the DATA Start signal (High, 80us) */
while((digitalRead(pin) == 1) && flag++);
RH_H = read_8bits();
RH_L = read_8bits();
T_H = read_8bits();
T_L = read_8bits();
crc = read_8bits();

pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH);
return 0;
}
else
return -1;
}

char DH21::read_8bits()
{
char i, flag, data = 0;
char temp;
for(i=0; i<8; i++)
{
flag = 2;
while((digitalRead(pin) == 0) && flag++);
delayMicroseconds(30);
temp = 0;
if(digitalRead(pin) == 1) temp = 1;
flag = 2;
while((digitalRead(pin) == 1) && flag++);
if(flag == 1) break;
data <<= 1;
data |= temp;
}
return data;
}

char DH21::data_check()
{
char tmp = (T_H + T_L + RH_H + RH_L);
if(tmp != crc)
{
RH_H = 0;
RH_L = 0;
T_H = 0;
T_L = 0;
return -1;
}
else
return 0;
}

float DH21::temperature()
{
uint16_t T = (T_H << 8) | T_L;
float tt;

if(T >= 0)
tt = T/10 + (T%10) * 0.1;
else
{
T = T & 0x7fff;
tt = -(T/10 + (T%10) * 0.1);
}

return tt;
}

float DH21::humidity()
{
uint16_t RH = (uint16_t)(RH_H << 8) | RH_L;
float hum;
hum = RH/10 + (RH%10) * 0.1;

return hum;
}
</source>

撰写自己的 Arduino 库 - 版本历史

Comcat：以“以 DHT21/AM2301 数字温湿度传感器 为例，示例如下 Arduino 封装的库都在 /PATH/TO/Arduino-1.0.1/libraries 下，因此我们自己写的库也...”为内容创建页面

Comcat：以“以 DHT21/AM2301 数字温湿度传感器为例，示例如下 Arduino 封装的库都在 /PATH/TO/Arduino-1.0.1/libraries 下，因此我们自己写的库也...”为内容创建页面