README

Parts

SKU: SEN0137
- https://www.dfrobot.com/product-1102.html
DFRobot DHT22 pinout
- left green pin is data/signal, middle red is vcc/5v, and right black is GND
Raspberry Pi 3 Model B Rev 1.2 or better

Connections at `*`

Left			Right
3.3v PWR	1	2	5V PWR
GPIO 2	3	4	5V PWR*
GPIO 3	5	6	GND*
GPIO 4*	7	8	UARTO TX

Dependencies

python3 and setup tools

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install python3-dev python3-pip
sudo python3 -m pip install --upgrade pip setuptools wheel
sudo pip3 install Adafruit_DHT

MQTT library https://www.eclipse.org/paho/index.php?page=clients/python/index.php

pip install paho-mqtt

Install with root home target for use in systemd script (-H)

sudo -H pip install paho-mqtt

Reading ENV vars

pip install python-dotenv

Install with root home target for use in systemd script (-H)

sudo -H pip install python-dotenv

Example `.env`

USERNAME=appuser1
PASSWORD=password1
HOST=192.168.10.226
PORT=1883

Basic Usage

python3 dht22.py

Systemd Usage

Create script

Run the following command and add the script data:

sudo vi /etc/systemd/system/dht22.service

[Unit]
Description=Send temperature and humidity values via MQTT
After=multi-user.target

[Service]
ExecStart=/usr/bin/python3 /home/pi/Documents/tempAndHumidity/dht22.py

[Install]
WantedBy=multi-user.target

Systemd Commands

chmod ugo+x dht22.py
systemctl enable dht22.service
systemctl start dht22.service
systemctl status dht22.service
systemctl stop dht22.service

# The text output of the script you will find in the journal:
journalctl -b -e

dht22 code ref

https://pimylifeup.com/raspberry-pi-humidity-sensor-dht22/

Notes

if context worked you could do the following but it doesnt work with python3

import context  # Ensures paho is in PYTHONPATH
import paho.mqtt.publish as publish

username="appuser1"
password="password1"
host = "192.168.10.226"
port = 1883
qos = 0
retain = False
client_id = ""
keepalive = 60
will=None
auth = { 'username': username, 'password': password }
tls=None
protocol=mqtt.MQTTv311,
transport="tcp"
topic = "JTL/temps/plant1"
payload = "This is a test..."


publish.single(topic,
    payload,
    qos,
    retain,
    host,
    port,
    client_id,
    keepalive,
    will,
    auth,
    tls,
    protocol,
    transport
)

jtlindsey/dht22-raspberrypi-python