circuitpython: adafruit_minimqtt produces non-descript error inside _wait_for_msg on Pico W

CircuitPython version

Adafruit CircuitPython 0.8.0-beta1; Raspberry Pi Pico W

Code/REPL

"""
Based on https://gist.github.com/sammachin/b67cc4f395265bccd9b2da5972663e6d
http://www.steves-internet-guide.com/into-mqtt-python-client/
"""
import json
from secrets import secrets

import board
import digitalio
import busio
import socketpool
import wifi
import microcontroller
from binascii import hexlify
from adafruit_minimqtt.adafruit_minimqtt import MQTT

SSID, PASSWORD = secrets["ssid"], secrets["password"]

BROKER = "test.mosquitto.org"

TEXT_URL = "http://wifitest.adafruit.com/testwifi/index.html"

pool = socketpool.SocketPool(wifi.radio)

wifi.radio.connect(SSID, PASSWORD)

uid = microcontroller.Processor.uid
my_id = hexlify(b"{uid}").decode()

prefix = f"sdl-demo/picow/{my_id}/"
print(f"prefix: {prefix}")

onboard_led = digitalio.DigitalInOut(board.LED)  # only works for Pico W
onboard_led.direction = digitalio.Direction.OUTPUT

def on_connect(client, userdata, flags, rc):
    print("Connected with result code " + str(rc))
    client.subscribe(prefix + "GPIO/#", qos=0)


def callback(topic, msg):
    t = topic.decode("utf-8").lstrip(prefix)
    print(t)

    if t[:5] == "GPIO/":
        p = int(t[5:])
        print(msg)
        data = json.loads(msg)
        onboard_led.value = data["value"]
        payload = {"onboard_led_value": onboard_led.value}
        print(payload)
        client.publish(prefix + "onboard_led/", payload, qos=0)


# The callback for when a PUBLISH message is received from the server.
def on_message(client, userdata, msg):
    print(msg.topic + " " + str(msg.payload))


# Set up a MiniMQTT Client
client = MQTT(
    client_id=prefix,
    broker=BROKER,
    username=None,
    password=None,
    is_ssl=False,
    socket_pool=pool,
)

client.connect()

client.add_topic_callback(prefix + "GPIO/#", callback)
client.on_connect = on_connect
client.on_message = on_message
client.subscribe(prefix + "GPIO/#")

while True:
    client.check_msg()

Behavior

prefix: sdl-demo/picow/<PICO ID>/
Traceback (most recent call last):
  File "<stdin>", line 87, in <module>
  File "adafruit_minimqtt/adafruit_minimqtt.py", line 741, in subscribe
  File "adafruit_minimqtt/adafruit_minimqtt.py", line 876, in _wait_for_msg
MMQTTException:

For reference: File "<stdin>", line 87, in <module> is:

client.connect()

EDIT:

client.subscribe(prefix + "GPIO/#")

https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT/blob/f2cb3bbe830f05cb75cd397fe83803ee1e59946b/adafruit_minimqtt/adafruit_minimqtt.py#L741

https://github.com/adafruit/Adafruit_CircuitPython_MiniMQTT/blob/f2cb3bbe830f05cb75cd397fe83803ee1e59946b/adafruit_minimqtt/adafruit_minimqtt.py#L861-L876

Description

• adafruit_minimqtt fails for Pico W

Additional information

I’ve been porting my MicroPython implementation at https://github.com/sparks-baird/self-driving-lab-demo/blob/main/src/public_mqtt_sdl_demo/main.py to CircuitPython. Part of the appeal of using CircuitPython is to use ArduCam, which only has C and CircuitPython support – no MicroPython support as far as I can tell https://github.com/ArduCAM/PICO_SPI_CAM/issues/8 https://github.com/namato/micropython-ov2640/issues/6. I’d be OK with another basic color camera, but had trouble finding one that looked like it would work as easily as ArduCam.

adafruit_minimqtt documentation