matrix_sensors.py

import os
import sys
from matrix_lite import sensors
from matrix_lite import led
import threading, time, signal
from datetime import timedelta
import paho.mqtt.client as mqtt
import json



broker_url = ""
broker_port = 1883
client = mqtt.Client()
client.username_pw_set("", "")
WAIT_TIME_SECONDS = 60

class ProgramKilled(Exception):
    pass

def signal_handler(signum, frame):
    raise ProgramKilled

class Job(threading.Thread):
    def __init__(self, interval, execute, *args, **kwargs):
        threading.Thread.__init__(self)
        self.daemon = False
        self.stopped = threading.Event()
        self.interval = interval
        self.execute = execute
        self.args = args
        self.kwargs = kwargs
        
    def stop(self):
                self.stopped.set()
                self.join()
    def run(self):
            while not self.stopped.wait(self.interval.total_seconds()):
                self.execute(*self.args, **self.kwargs)


def get_cpu_temp():
    """Get CPU temperature."""
    res = os.popen("vcgencmd measure_temp").readline()
    t_cpu = float(res.replace("temp=", "").replace("'C\n", ""))
    return t_cpu

def get_average(temp_base):
    """Use moving average to get better readings."""
    if not hasattr(get_average, "temp"):
        get_average.temp = [temp_base, temp_base, temp_base]
    get_average.temp[2] = get_average.temp[1]
    get_average.temp[1] = get_average.temp[0]
    get_average.temp[0] = temp_base
    temp_avg = (get_average.temp[0] + get_average.temp[1]
                + get_average.temp[2]) / 3
    return temp_avg

def on_message(client, userdata, message):
    # print("Message Recieved: "+message.payload.decode())
    payload = json.loads(message.payload.decode())
    if payload['value']:
        value = payload['value']
        led.set(value)

def printText(data):
    print(data)
    sys.stdout.flush()

def updateSensors():
   temp_from_h = sensors.humidity.read().temperature
   printText("temp from humidity: " + str(temp_from_h))
   temp_from_p = sensors.pressure.read().temperature
   printText("temp from pressure: " + str(temp_from_p))
   t_total = (temp_from_h + temp_from_p) / 2
   printText("total of 2: " + str(t_total))
   t_cpu = get_cpu_temp()
   t_correct = t_total - ((t_cpu - t_total) / 1.5)
   t_correct = get_average(t_correct)

   temperature = str("%.2f" % round(t_correct,2))
   humidity = str("%.2f" % round(sensors.humidity.read().humidity,2))
   pressure = str("%.2f" % round(sensors.pressure.read().pressure,2))
   uv = str("%.2f" % round(sensors.uv.read().uv,2))
   printText("Temp: " + temperature + " humidity: "+ humidity +" pressure: "+ pressure +" UV:" + uv)
   client.publish(topic="homeassistant/sensor/sensorMatrix/state", payload='{"temperature": '+ temperature +', "humidity": '+ humidity +', "pressure": '+ pressure +', "uv": '+ uv +'}', qos=1, retain=False)

if __name__ == "__main__":
   signal.signal(signal.SIGTERM, signal_handler)
   signal.signal(signal.SIGINT, signal_handler)
   client.on_message = on_message
   client.connect(broker_url, broker_port)
   client.loop_start()
   client.subscribe("homeassistant/light/ledMatrix", qos=0)
   client.publish(topic="homeassistant/sensor/sensorMatrixTemp/config", payload='{"device_class": "temperature", "name": "Temperature", "state_topic": "homeassistant/sensor/sensorMatrix/state", "unit_of_measurement": "°C", "value_template": "{{ value_json.temperature}}" }', qos=1, retain=True)
   client.publish(topic="homeassistant/sensor/sensorMatrixHum/config", payload='{"device_class": "humidity", "name": "Humidity", "state_topic": "homeassistant/sensor/sensorMatrix/state", "unit_of_measurement": "%", "value_template": "{{ value_json.humidity}}" }', qos=1, retain=True)
   client.publish(topic="homeassistant/sensor/sensorMatrixPres/config", payload='{"device_class": "pressure", "name": "Pressure", "state_topic": "homeassistant/sensor/sensorMatrix/state", "unit_of_measurement": "Pa", "value_template": "{{ value_json.pressure}}" }', qos=1, retain=True)
   client.publish(topic="homeassistant/sensor/sensorMatrixUv/config", payload='{"name": "UV", "state_topic": "homeassistant/sensor/sensorMatrix/state", "value_template": "{{ value_json.uv}}" }', qos=1, retain=True)
   updateSensors()
   job = Job(interval=timedelta(seconds=WAIT_TIME_SECONDS), execute=updateSensors)
   job.start()
   
   
   while True:
         try:
            time.sleep(1)
         except ProgramKilled:
            print ("Program killed: running cleanup code")
            sys.stdout.flush()
            job.stop()
            break
   
   

# print(sensors.uv.read())

# print(sensors.pressure.read())

Hi, did you ever got anything nearly useful out of the temperature sensors from this board? I saw your CPU-temp correction code here but the values I get are nowhere usefull.

I wonder if the sensors on this board are usefull at all.. The humidity sensor itself is based on the temperature so the values are also inaccurate or at least has to be corrected as well.

It depends off where the board is placed. If you place it directly on the PI you will need a different calculation then when you place it somewhere else with a GPIO cable. You get the temp of 2 different sensors: the pressure sensor and the humidity sensor.

What I did was take a sensor (or something else like a thermostat) and note down that value and also note down the value of the sensors of the matrix board. Do this every minute or so for like 100min. Then you can calculate the formula for the calibrated temp.

Thank you. I will try with a cable to get the board at some distance to the RPi and see what the difference is then.