Home Assistant Weather

Handling data from Ambient Weather WS-2902C API to MQTT

Handling data from Ambient Weather WS-2902C API to MQTT

As I mentioned in my initial Ambient Weather WS-2902C post, there is a new feature that allows sending data to a custom server. I coded up a python script to take the sent data, and publish it to MQTT. This allows for super easy data ingestion with Home Assistant and other similar solutions. I should probably publish on GitHub but I’ll post here first.


This script is reliant on Paho-MQTT. EDIT: during the creation of the service to run this at boot, I discovered version 1.5.1 will throw errors. Use version 1.5.0. Install it with pip:

sudo pip install paho-mqtt==1.5.0

Create a python file and name it Paste in the following:

# Python script to decode Ambient Weather data (from WS-2902C and similar)
# and publish to MQTT.
# original author: Austin of
# publish date: 2021-03-20

# some resources I used include

from urllib.parse import urlparse, parse_qs
import paho.mqtt.client as mqtt
import time, os

# set MQTT vars
MQTT_BROKER_HOST  = os.getenv('MQTT_BROKER_HOST',"mqtt")
MQTT_BROKER_PORT  = int(os.getenv('MQTT_BROKER_PORT',1883))
MQTT_CLIENT_ID    = os.getenv('MQTT_CLIENT_ID',"ambient_weather_decode")
MQTT_USERNAME     = os.getenv('MQTT_USERNAME',"")
MQTT_PASSWORD     = os.getenv('MQTT_PASSWORD',"")

# looking to get resultant topic like weather/ws-2902c/[item]
MQTT_TOPIC_PREFIX = os.getenv('MQTT_TOPIC_PREFIX',"weather")
MQTT_TOPIC 		  = MQTT_TOPIC_PREFIX + "/ws-2902c"

# mostly copied + pasted from and some of my own MQTT scripts
def on_connect(client, userdata, flags, rc):
    if rc == 0:
        print(f"connected to MQTT broker at {MQTT_BROKER_HOST}")
        print("Failed to connect, return code %d\n", rc)

def on_disconnect(client, userdata, flags, rc):
    print("disconnected from MQTT broker")

# set up mqtt client
client = mqtt.Client(client_id=MQTT_CLIENT_ID)
    print("Username and password set.")
client.will_set(MQTT_TOPIC_PREFIX+"/status", payload="Offline", qos=1, retain=True) # set LWT     
client.on_connect = on_connect # on connect callback
client.on_disconnect = on_disconnect # on disconnect callback

# connect to broker

def publish(client, topic, msg):
    result = client.publish(topic, msg)
    # result: [0, 1]
    status = result[0]

    # uncomment for debug. don't need all the success messages.
    if status == 0:
        #print(f"Sent {msg} to topic {topic}")
        print(f"Failed to send message to topic {topic}")

def application(environ, start_response):
    # construct a full URL from the request. HTTP_HOST is FQDN, PATH_INFO is everything after
    # the FQDN (i.e. /data/stationtype=AMBWeatherV4.2.9&&tempinf=71.1&humidityin=35)
    url = "http://" + environ["HTTP_HOST"] + environ["PATH_INFO"]

    # unsure why I need to parse twice. probably just need to do it once with variable url.
    parsed = urlparse(url)
    result = parse_qs(parsed.geturl())

    # send to our other function to deal with the results.
    # result is a dict 

    # we need to return a response. HTTP code 200 means everything is OK. other HTTP codes include 404 not found and such.
    start_response('200 OK', [('Content-Type', 'text/plain')])

    # the response doesn't actually need to contain anything
    response_body = ''

    # return the encoded bytes of the response_body. 
    # for python 2 (don't use python 2), the results don't need to be encoded
    return [response_body.encode()]

def handle_results(result):
    """ result is a dict. full list of variables include:
    stationtype: ['AMBWeatherV4.2.9'], PASSKEY: ['<station_mac_address>'], dateutc: ['2021-03-20 17:12:27'], tempinf: ['71.1'], humidityin: ['36'], baromrelin: ['29.693'],	baromabsin: ['24.549'],	tempf: ['58.8'], battout: ['1'], humidity: ['32'], winddir: ['215'],windspeedmph: ['0.0'],	windgustmph: ['0.0'], maxdailygust: ['3.4'], hourlyrainin: ['0.000'],	eventrainin: ['0.000'],	dailyrainin: ['0.000'],
    weeklyrainin: ['0.000'], monthlyrainin: ['0.000'], totalrainin: ['0.000'],	solarradiation: ['121.36'],
    uv: ['1'],batt_co2: ['1'] """

    # we're just going to publish everything. less coding.
    for key in result:
        # skip first item, which is basically a URL and MQTT doesn't like it. probably resulting from my bad url parsing.
        if 'http://' in key:

        #print(f"{key}: {result[key]}")
        # resultant topic is weather/ws-2902c/solarradiation
        specific_topic = MQTT_TOPIC + f"/{key}"

        # replace [' and '] with nothing. these come from the url parse
        msg = str(result[key]).replace("""['""", '').replace("""']""", '')
        #print(f"attempting to publish to {specific_topic} with message {msg}")
        publish(client, specific_topic, msg)

# this little guy runs a web server if this python file is called directly. if it isn't called directly, it won't run.
# Apache/Python WSGI will run the function 'application()' directly
# in theory, you don't need apache or any webserver. just run it right out of python. would need
# to improve error handling to ensure it run without interruption.
if __name__ == '__main__':
    from wsgiref.simple_server import make_server

    # probably shouldn't run on port 80 but that's what I specified in the ambient weather console
    httpd = make_server('', 80, application)
    print("Serving on http://localhost:80")


Execute with python3:


Watch the results populate in the console window:

PS C:\Users\Austin\source\repos\ambient-weather-decode> python3 c:\Users\Austin\source\repos\ambient-weather-decode\
connected to MQTT broker at mqtt
Serving on http://localhost:80
Sent E0:98:06:A3:42:65 to topic weather/ws-2902c/PASSKEY
Sent 2021-03-20 17:57:31 to topic weather/ws-2902c/dateutc
Sent 70.7 to topic weather/ws-2902c/tempinf
Sent 36 to topic weather/ws-2902c/humidityin
Sent 29.675 to topic weather/ws-2902c/baromrelin
Sent 24.531 to topic weather/ws-2902c/baromabsin
Sent 66.2 to topic weather/ws-2902c/tempf
Sent 1 to topic weather/ws-2902c/battout
Sent 26 to topic weather/ws-2902c/humidity
Sent 207 to topic weather/ws-2902c/winddir
Sent 0.2 to topic weather/ws-2902c/windspeedmph
Sent 1.1 to topic weather/ws-2902c/windgustmph
Sent 3.4 to topic weather/ws-2902c/maxdailygust
Sent 0.000 to topic weather/ws-2902c/hourlyrainin
Sent 0.000 to topic weather/ws-2902c/eventrainin
Sent 0.000 to topic weather/ws-2902c/dailyrainin
Sent 0.000 to topic weather/ws-2902c/weeklyrainin
Sent 0.000 to topic weather/ws-2902c/monthlyrainin
Sent 0.000 to topic weather/ws-2902c/totalrainin
Sent 697.92 to topic weather/ws-2902c/solarradiation
Sent 6 to topic weather/ws-2902c/uv
Sent 1 to topic weather/ws-2902c/batt_co2


Verify in MQTT by subscribing to topic ‘weather/#’. The # is a wildcard and will include all subtopics:

homeassistant ws-2902c mqtt messages
homeassistant ws-2902c mqtt messages


I am stoked the Ambient Weather WS-2902C makes it so easy to work the the data.

My next post will show how to turn this Python script into a persistent Linux service – Python service to consume Ambient Weather API data.

A further post will demonstrate incorporating these MQTT messages into Home Assistant sensors.

4 replies on “Handling data from Ambient Weather WS-2902C API to MQTT”

Awesome post! Thank you for taking the time to share this. You saved me a ton of time trying to figure this out on my own.
A suggestion to give back a little…
In your, you had a comment about not liking the way you parsed the URL. In the weather station setup, if you set the Path to: /data? the resulting environ in your python program will split the query from the path, so you don’t have to rebuild the URL and parse it twice. “result = parse_qs(environ[‘QUERY_STRING’]) will give you what you want.
Please keep posting articles like this – love what you’re doing!

Looks great; I dont see a github repo; would make taking suggestions from open source community easier;

also i am interested in seeing if this could be put into a very small docker container; Just bought mine today; might look into this over winter break!

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