Creating a temperature / humidity monitor with Raspberry Pi (pigpio version)

Change GPIO control to pigpio and get temperature and humidity value from DHT22. I felt that it would be better to move to pigpio to control other sensors in the future, so I remade the one created with MyPyDHT.

Creating a temperature / humidity monitor with Raspberry Pi This is the pigpio version of.

Advance preparation

Install pigpio on your Raspberry Pi as shown on this web site. http://abyz.me.uk/rpi/pigpio/download.html

For the time being, just execute the command below.

sudo apt-get update
sudo apt-get install pigpio python-pigpio python3-pigpio

sudo pigpiod

The DHT control code was also on the pigpio author's Examples page and will be used as is. http://abyz.me.uk/rpi/pigpio/code/DHT.py

Use RasPi + FastAPI

Connection of DHT22 sensor and Raspberry Pi

The DAT terminal is connected to GPIO4, and 5V is given to VCC.

file organization

File	Explanation
templates/index.html	Get data every 5 seconds with HTML file and JavaScript
dht_server.py	Includes sensor processing for Python server, DHT22
DHT.py	pigpio author's DHT sensor control code (DHT11)/21/22/33/44) seems to be automatically supported

Main control of DHT22

If you execute the GPIO value with the DHT control code (DHT.py) as an argument, the greenhouse degree value will be acquired by the callback control if you add +100 to the GPIO value every 2 seconds.

python DHT.py 4
or
python DHT.py 104

Extract only the main process from DHT.py and write the code to get the greenhouse degree value every 2 seconds when it is executed. Save DHT.py in the same folder. You will post this code to the server later.

`dht22_pigpio.py`


import time
import DHT
import pigpio
import datetime

DHT_PIN = 4 

if __name__== "__main__":
    pi = pigpio.pi()
    if not pi.connected:
        print(f"cannot connect to pigpio")
        exit()

    s = DHT.sensor(pi, DHT_PIN)

    while True:
        try:
            d = s.read()
            today = datetime.datetime.fromtimestamp(d[0]).strftime ("%Y/%m/%d %H:%M" )
            temperature = d[3]
            humidity = d[4]
            dat = {"time": today, "temperature": temperature, "humidity": humidity}
            print(f"json: {dat}")
            time.sleep(2)
        except KeyboardInterrupt:
            break

    s.cancel()
    print(f"cancelling")
    pi.stop()

html code

Use fetch from the Python server to get temperature and humidity information every 5 seconds. (Same as last time)

`index.html`


<!DOCTYPE html>
<html lang="ja">

<head>
    <title>Temperature / humidity monitoring monitor</title>
</head>

<body>
    <div>
        <div class="container">
            <h1>Temperature / humidity monitoring monitor</h1>
            <h2 id="time">time</h2>
            <h2 id="temperature">temperature</h2>
            <h2 id="humidity">humidity</h2>
        </div>
    </div>
    <script>
        //Obtaining greenhouse degree value from server
        var sensor_read = function () {
            fetch("/data", {
                method: 'GET'
            }).then((response) => {
                return response.json();
            }).then((data) => {
                console.log(data);
                var time = document.querySelector("#time")
                time.innerHTML = data.time
                var temperature = document.querySelector("#temperature")
                temperature.innerHTML = `temperature:${data.temperature}Every time`
                var humidity = document.querySelector("#humidity")
                humidity.innerHTML = `Humidity:${data.humidity}％`
            }).catch((err) => {
                console.error(err);
            });
        };

　　　　 //5 second timer
        setInterval(sensor_read, 5000);
    </script>
</body>

</html>

Python code

Pass temperature/humidity data with Dict when accessing/data.

`dht_server.py`


import uvicorn
from fastapi import FastAPI
from starlette.templating import Jinja2Templates
from starlette.requests import Request
import datetime
import DHT
import pigpio

app = FastAPI()

templates = Jinja2Templates(directory="templates")
jinja_env = templates.env

DHT_PIN = 4 
sensor = None

@app.get("/")
def root(request: Request):
    return templates.TemplateResponse('index.html',
                                      {'request': request})

@app.get("/data")
def data():
    """Returns temperature and humidity values"""
    try:
        data = sensor.read()
        today = datetime.datetime.fromtimestamp(data[0]).strftime ("%Y/%m/%d %H:%M")
        status = data[2]
        temperature = data[3]
        humidity = data[4]
        if status == DHT.DHT_GOOD:
            dat = {"time": today, "temperature": temperature, "humidity": humidity}
            print(f"json: {dat}")
            return dat
        else:
            raise Exception(f"dht sensor error: {status}")
    except Exception as e:
        print(f"err: {str(e)}")

    return None


if __name__ == "__main__":
    pi = pigpio.pi()
    if not pi.connected:
        print(f"cannot connect to pigpio")
        exit()

    sensor = DHT.sensor(pi, DHT_PIN)
    #Server startup
    uvicorn.run(app, host="0.0.0.0", port=8000)

    sensor.cancel()
    print(f"cancelling")
    pi.stop()

Start the server.

Check the IP of the Raspberry Pi and access it with a browser. Please check 0.0.0.0 with ifconfig etc. on Raspberry Pi and replace it.

 $ python dht_server.py