Issues with combining micropython-async (Encoder) and mqtt_as

[IanW6374]

I am starting to build a basic IoT device and experimenting with mqtt_as and micropython-async (Encoder / Pushbutton drivers) to provide the basic functionality.

As a test I have combined the basic examples for each library so that when a button is pressed or the encoder value changes it will publish a MQTT message. Everything works as expected for the Pushbutton, however, when the encoder callback function is triggered nothing happens. This seems to be related to the await client.publish('Result', '{}'.format(data1), qos = 0) line as if this is commented out then I get the print output.

Any input would be gratefully received :)

The test code is shown below (minus the MQTT config)

from mqtt_as import MQTTClient, config
import asyncio
from machine import Pin
from primitives import Encoder, Pushbutton

def local_input(data1, data2):
    
    print ('****', data1, data2)
    await client.publish('Result', '{}'.format(data1), qos = 0)


px = Pin(2, Pin.IN, Pin.PULL_UP)  # Change to match hardware
py = Pin(3, Pin.IN, Pin.PULL_UP)
sw = Pushbutton(Pin(4), Pin.IN, Pin.PULL_UP)
    
enc = Encoder(px, py, div=4, callback=local_input)  # div mtches mechanical detents    
sw.press_func(local_input, (4,'Test'))


async def messages(client):  # Respond to incoming messages
    async for topic, msg, retained in client.queue:
        print((topic, msg, retained))

async def up(client):  # Respond to connectivity being (re)established
    while True:
        await client.up.wait()  # Wait on an Event
        client.up.clear()
        await client.subscribe('foo_topic', 1)  # renew subscriptions

async def main(client):
     
    await client.connect()
    for coroutine in (up, messages):
        asyncio.create_task(coroutine(client))
    n = 0
    while True:
        await asyncio.sleep(5)
        print('publish', n)
        # If WiFi is down the following will pause for the duration.
        await client.publish('result', '{}'.format(n), qos = 1)
        n += 1

config["queue_len"] = 1  # Use event interface with default queue size
MQTTClient.DEBUG = True  # Optional: print diagnostic messages
client = MQTTClient(config)
try:
    asyncio.run(main(client))
finally:
    client.close()  # Prevent LmacRxBlk:1 errors

[dennis6101990leon]

Hello,

There are two possible approaches to fix this:

Use a callback for publish:
Instead of using await, modify the local_input function to take a callback function as an argument. This callback can be called after the publishing is complete (if the library supports it). Here's an example:

`def local_input(data1, data2, publish_callback):
print ('****', data1, data2)
Call publish in a separate thread or use a callback if supported
publish_callback healthinsurancemarket ('Result', '{}'.format(data1), qos = 0)

rest of your code

def publish_message(topic, message, qos):
client.publish(topic, message, qos)
Handle any errors here

enc = Encoder(px, py, div=4, callback=lambda d1, d2: local_input(d1, d2, publish_message))
`
Run publish in a separate task:
If the library doesn't support callbacks for publish, you can create a separate asyncio task to handle the publishing. This allows local_input to continue execution without waiting for the publish to finish.

`async def publish_message(topic, message, qos):
await client.publish(topic, message, qos)

def local_input(data1, data2):
print ('****', data1, data2)
asyncio.create_task(publish_message('Result', '{}'.format(data1), qos = 0))

rest of your code
`
By implementing one of these solutions, the local_input function shouldn't block when publishing the message, and you should receive the encoder callback along with the button press functionality.

[IanW6374]

Hi Dennis - Thanks for your response

I can confirm that your suggested option 2 resolves the issue :). Thanks for your quick response - It is much appreciated !!