[嵌入式]raspberrypi通过mqtt协议将DHT22数据发送给broker

1. 确保Raspberry Pi上有最新的更新

sudo apt-get update

2. 安装python 3-dev和python3-pip使用这两个包来与湿度传感器进行交互

sudo apt-get install python3-dev python3-pip

3. 安装最新版本的setuptools、wheel和pip python包。

sudo python3 -m pip install --upgrade pip setuptools wheel 

4. 将DHT库安装到Raspberry Pi上

sudo pip3 install Adafruit_DHT

5. 下载库

pip install paho-mqtt

基于MQTT协议在树莓派上利用DHT22温湿度传感器测量温湿度，并且持续发布主题为:temphum，内容为温湿度的消息。

发布端程序（文件名.py）：

import paho.mqtt.publish as publish
import Adafruit_DHT
import time
sensor = Adafruit_DHT.DHT22
pin = 27
while True:
           hu,temp =Adafruit_DHT.read_retry(sensor,pin)  //测量
           humtemp = 'temp:{0:0.1f}*C hu:{1}%'.format(temp,hu)
           publish.single("temphum",payload=humtemp,qos=0,
                    hostname="***.***.***.***")   //edge节点ip或者localhost
           time.sleep(2)

订阅端程序(文件名.py)：

# encoding: utf-8
#!/user/bin/env python
 
import paho.mqtt.client as mqtt
import paho.mqtt.publish as publish
import RPi.GPIO as GPIO
import json
import time
 
 
#订阅
#一旦连接成功回调函数
def on_connect(client,userdata,flags,rc):
    print("Connected with result code " + str(rc))
 
# 一旦订阅成功回调函数
def on_message(client,userdata,msg):
    print(msg.topic+" "+str(msg.payload))
 
#一旦订阅成功回调函数
def on_subscribe(client,userdata,mid,granted_qos):
    print("Subscribed: " + str(mid) + str(granted_qos))
 
 
if __name__=='__main__':
     client = mqtt.Client()
     client.on_connect = on_connect
     client.on_message = on_message
     client.on_subscribe = on_subscribe
     client.connect("***.***.***.***",1883,60)  //edge节点ip或者localhost
     client.subscribe("temphum",0)
     client.loop_forever()

服务器使用:mosquitto

程序全部在树莓派上运行

1. 先运行订阅端脚本

python3 name.py

2. 运行发布端脚本

python3 name.py

注意事项：
确保raspberrypi作为edge节点，并处于ready状态。