Friday, February 4, 2022

[SOLVED] Trying to send one message via MQTT and sleep for 5 seconds

Issue

I am currently trying to send a message via MQTT protocol which works. I am using a raspberry Pi and a vibration sensor as a means to trigger the sending of the message. At the start I would touch the sensor and it would send loads of messages at once which is what I dont want to happen. so I tried to make it sleep for 5 seconds after it detects vibration. But now it detects one vibration and then wont detect another one but doesnt stop the running of the file. the only way i can get it to detect the vibration again is to run the file again. here is the two ways I tried:

import time
from grove.gpio import GPIO

import paho.mqtt.client as mqttClient


class GrovePiezoVibrationSensor(GPIO):
    def __init__(self, pin):
        super(GrovePiezoVibrationSensor, self).__init__(pin, GPIO.IN)
        self._on_detect = None

    @property
    def on_detect(self):
        return self._on_detect

    @on_detect.setter
    def on_detect(self, callback):
        if not callable(callback):
            return

        if self.on_event is None:
            self.on_event = self._handle_event

        self._on_detect = callback

    def _handle_event(self, pin, value):
        if value:
            if callable(self._on_detect):
                self._on_detect()
                time.sleep(5000)


Grove = GrovePiezoVibrationSensor
def on_connect(client, userdata, flags, rc):

    if rc == 0:

        print("Connected to broker")

        global Connected                #Use global variable
        Connected = True                #Signal connection

    else:

        print("Connection failed")

Connected = False   #global variable for the state of the connection

broker_address= "hairdresser.cloudmqtt.com"
port = 15767
user = "kprpjfue"
password = "1fIq2_CIwHZj"
client = mqttClient.Client("Python")               #create new instance
client.username_pw_set(user, password=password)    #set username and password
client.on_connect= on_connect
client.loop_start()

client.connect(broker_address, port=port)



def main():
    from grove.helper import SlotHelper
    sh = SlotHelper(SlotHelper.GPIO)
    pin = sh.argv2pin()

    pir = GrovePiezoVibrationSensor(pin)

    def callback():
        print('Detected.')
        value = 'detected'
        client.publish("sensor/Temp", value)

    pir.on_detect = callback
    while True:
        time.sleep(5000)

if __name__ == '__main__':
    main()


while Connected != True:    #Wait for connection
    time.sleep(0.1)


import time
from grove.gpio import GPIO

import paho.mqtt.client as mqttClient


class GrovePiezoVibrationSensor(GPIO):
    def __init__(self, pin):
        super(GrovePiezoVibrationSensor, self).__init__(pin, GPIO.IN)
        self._on_detect = None

    @property
    def on_detect(self):
        return self._on_detect

    @on_detect.setter
    def on_detect(self, callback):
        if not callable(callback):
            return

        if self.on_event is None:
            self.on_event = self._handle_event

        self._on_detect = callback

    def _handle_event(self, pin, value):
        if value:
            if callable(self._on_detect):
                self._on_detect()
                time.sleep(5000)


Grove = GrovePiezoVibrationSensor
def on_connect(client, userdata, flags, rc):

    if rc == 0:

        print("Connected to broker")

        global Connected                #Use global variable
        Connected = True                #Signal connection

    else:

        print("Connection failed")

Connected = False   #global variable for the state of the connection

broker_address= "hairdresser.cloudmqtt.com"
port = 15767
user = "kprpjfue"
password = "1fIq2_CIwHZj"
client = mqttClient.Client("Python")               #create new instance
client.username_pw_set(user, password=password)    #set username and password
client.on_connect= on_connect

client.connect(broker_address, port=port)



def main():
    from grove.helper import SlotHelper
    sh = SlotHelper(SlotHelper.GPIO)
    pin = sh.argv2pin()

    pir = GrovePiezoVibrationSensor(pin)

    def callback():
        print('Detected.')
        value = 'detected'
        client.publish("sensor/Temp", value)

    pir.on_detect = callback
    while True:
        time.sleep(5000)
        client.loop()

if __name__ == '__main__':
    main()


while Connected != True:    #Wait for connection
    time.sleep(0.1)

As you can see under the if callable in the handle event method I told I say time.sleep(5000). Am I putting this in the wrong place?


Solution

You have not started the MQTT client network loop so it will not be able receive messages or send a message large the the MTU.

You will also get disconnected after the keep alive period.

Add client.loop_start() before the call to client.connect()

or insert client.loop() after the time.sleep(5000) in the loop in main and it will be better to make it 1000 to the client loop runs at least once a second.

Adding sleeps in callbacks is normally a bad idea as it doesn't stop events from being triggered it just delays them, because they will just be queued up until the sleep times out.

You should set a flag on the first event just after sending the MQTT message which you can then expire using the While True loop in main. If a new event comes in while the flag is still set then you just don't send another MQTT message.



Answered By - hardillb
Answer Checked By - Willingham (WPSolving Volunteer)
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