MQTT with an Arduino Nano RP2040 Connect

[ScooterKraig]

I am trying to get an Arduino Nano RP2040 Connect board to run as an MQTT publisher. This is another case for me where the code works (usually) on a real Raspberry Pi Pico W, but not on the Arduino board. I was previously having trouble with other network connections; see https://github.com/orgs/micropython/discussions/18901. Here was a solution for my NTP time problem that worked for both the Arduino and the Raspberry. I'm hoping someone has a solution for MQTT, or at least some insights as to what's going on. Thanks for any help.

import network
import socket
import struct
import select
from time import gmtime, localtime, sleep
from machine import Pin, RTC
from umqttsimple import MQTTClient
from secrets import ssid, password
#import nina_rgb

rtc = RTC()

led = Pin("LED", Pin.OUT)
blue_led = Pin(16, Pin.OUT)

#mqtt config
mqtt_server = 'thermostat-b.local'
client_id = 'Number-7'
user_t = ''
password_t = ''
topic_pub = '7-test'
topic_sub = 'Number-8-test'
time_server = b'pool.ntp.org'

# connect to WiFi
def connect_wifi():
    wlan = network.WLAN(network.STA_IF)
    wlan.active(True)
    count = 1
    while not wlan.isconnected():
#        print('connection: ',wlan.isconnected())
        print('connection tries',count)
        wlan.connect(ssid, password)
        sleep(2)
        count += 1
        
    print('connected??', wlan.isconnected())
    print('wlan status', wlan.status()) 
    print( 'ip: ', wlan.ifconfig()[0] )
    blue_led.on()

def ntp_time(hrs_offset=-5):  # Local time offset in hrs relative to UTC
    NTP_DELTA = 3155673600 if gmtime(0)[0] == 2000 else 2208988800
    NTP_QUERY = bytearray(48)
    NTP_QUERY[0] = 0x1B
    connect_wifi()
    try:
        addr = socket.getaddrinfo(time_server, 123)[0][-1]
        print('addr = ', addr)
    except OSError:
        return 0
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    poller = select.poll()
    print('Poller: ',poller,select.POLLIN)
    poller.register(s, select.POLLIN)
    try:
        s.sendto(NTP_QUERY, addr)
        if poller.poll(1000):  # time in milliseconds
            msg = s.recv(48)
            val = struct.unpack("!I", msg[40:44])[0]  # Can return 0
            return max(val - NTP_DELTA + hrs_offset * 3600, 0)
    except OSError:
        pass  # LAN error
    finally:
        s.close()
    return 0  # Timeout or LAN error occurred

def set_rtc():
    print(ntp_time())
    if ntp_time() == 0:
        return False
    else:
        tm = localtime(ntp_time())
        # Monday to Sunday - 0 to 6 weekdays
        rtc.datetime((tm[0], tm[1], tm[2], tm[6] + 1, tm[3], tm[4], tm[5], 0))
        return True


#==========================================================

#   Here's the part that doesn't work



#MQTT connect
def mqtt_connect():
    client = MQTTClient(client_id, mqtt_server, user=user_t, password=password_t, keepalive=60) # 
    print('client: ',client)
    sleep(5)
    try:
        client.connect()
        print(client, "connected...")
        print('Connected to %s MQTT Broker' % (mqtt_server))
        blue_led.on()
#        nina_rgb.ninapin_digital_write(nina_rgb.LEDB, 1)
    except:
#        blue_led.off()
        print("Failed to connect to MQTT Broker %s" % (mqtt_server))
        mqtt_reconnect()

    client.set_callback(sub_cb)
    client.subscribe("Number-8-test")
    print("Connected to %s, subscribed to %s topic" % (mqtt_server, topic_sub))
    sleep(5)
    return client

#==========================================================



#reconnect & reset
def mqtt_reconnect():
    print('Failed to connect to MQTT Broker. Reconnecting...')
    sleep(5)
    mqtt_connect()

def log():
    print("log...")
    client = mqtt_connect()
    now = localtime()
    y = "Test message"
    x = ("Pico 7: {}/{}/{}, {}:{:02}, {}".format(now[1], now[2], now[0], now[3], now[4], y))
    client.publish(topic_pub, msg=x, qos=0)
    print('Published ',x,"\n")
    client.disconnect()
    blue_led.off()

def sub_cb(topic,msg):
    print("Subscribed message: ",topic,msg)

############## Main ##############

led.off()
blue_led.off()
#connect_wifi()
#get time and set the RTC
if set_rtc():
    pass
else:
    raise Exception("Could not set RTC")

print('localtime:    ',localtime())
print('rtc.datetime: ',rtc.datetime())

sleep(5)
print('localtime:    ',localtime())
print('rtc.datetime: ',rtc.datetime())

# client = mqtt_connect()
sleep(10)

while True:
    log()
    sleep(20)
    pass

Arduino results:

MPY: soft reboot
connection tries 1
connected?? True
wlan status True
ip:  192.168.1.190
addr =  ('104.152.220.5', 123)
Poller:  <poll> 1
1773134958
connected?? True
wlan status True
ip:  192.168.1.190
addr =  ('104.152.220.5', 123)
Poller:  <poll> 1
connected?? True
wlan status True
ip:  192.168.1.190
addr =  ('104.152.220.5', 123)
Poller:  <poll> 1
localtime:     (2026, 3, 10, 9, 29, 20, 1, 69)
rtc.datetime:  (2026, 3, 10, 1, 9, 29, 20, 0)
localtime:     (2026, 3, 10, 9, 29, 25, 1, 69)
rtc.datetime:  (2026, 3, 10, 1, 9, 29, 25, 0)
log...
client:  <MQTTClient object at 2000ae60>
Failed to connect to MQTT Broker thermostat-b.local
Failed to connect to MQTT Broker. Reconnecting...
client:  <MQTTClient object at 2000bdd0>
Failed to connect to MQTT Broker thermostat-b.local
Failed to connect to MQTT Broker. Reconnecting...
client:  <MQTTClient object at 2000c1c0>
Failed to connect to MQTT Broker thermostat-b.local
Failed to connect to MQTT Broker. Reconnecting...

Raspberry results:

MPY: soft reboot
connected?? True
wlan status 3
ip:  192.168.1.193
addr =  ('198.23.133.146', 123)
Poller:  <poll> 1
1773133704
connected?? True
wlan status 3
ip:  192.168.1.193
addr =  ('198.23.133.146', 123)
Poller:  <poll> 1
connected?? True
wlan status 3
ip:  192.168.1.193
addr =  ('198.23.133.146', 123)
Poller:  <poll> 1
localtime:     (2026, 3, 10, 9, 8, 25, 1, 69)
rtc.datetime:  (2026, 3, 10, 1, 9, 8, 25, 0)
localtime:     (2026, 3, 10, 9, 8, 30, 1, 69)
rtc.datetime:  (2026, 3, 10, 1, 9, 8, 30, 0)
log...
client:  <MQTTClient object at 2000f7b0>
<MQTTClient object at 2000f7b0> connected...
Connected to thermostat-b.local MQTT Broker
Connected to thermostat-b.local, subscribed to Number-8-test topic
Published  Pico 7: 3/10/2026, 9:08, Test message 

log...
client:  <MQTTClient object at 20011500>
<MQTTClient object at 20011500> connected...
Connected to thermostat-b.local MQTT Broker
Connected to thermostat-b.local, subscribed to Number-8-test topic

[beetlegigg]

My arduino rp2040 connect board was still on my desk from trying the network sockets issue you had a couple of days ago, but sadly this time I can only confirm a problem. A simple test snippet for the mqttsimple module ran OK on the rpi picoW but failed on the arduino rp2040.

For me it failed on self.sock.connect(addr) in the connect function in mqttsimple. I put a try / except around this line:

try:
    self.sock.connect(addr)
except Exception as error:
    print("An error occurred:", error)

and got "An error occurred: no available NIC"

Maybe someone will understand whats going wrong with the arduino rp2040 network/wifi module, but for me this board is back in the useless drawer again :(

[beetlegigg]

Well I just posted in too much haste! I had put an auto connect to wifi in the rpi pico and forgot about it in the arduino rp2040.
So here is a working example using mqttsimple running on the aruino board.

import time
from umqttsimple import MQTTClient
import ubinascii
import machine
import network

from secrets import SSID, PW
mqtt_server = "10.0.1.141"

client_id = ubinascii.hexlify(machine.unique_id())

topic_sub = b'notification'
topic_pub = b'hello'

last_message = 0
message_interval = 5
counter = 0

# Complete project details at https://RandomNerdTutorials.com

def sub_cb(topic, msg):
  print((topic, msg))
  if topic == b'notification' and msg == b'received':
    print('received hello message')

def connect_and_subscribe():
  global client_id, mqtt_server, topic_sub
  client = MQTTClient(client_id, mqtt_server)
  client.set_callback(sub_cb)
  client.connect()
  client.subscribe(topic_sub)
  print('Connected to %s MQTT broker, subscribed to %s topic' % (mqtt_server, topic_sub))
  return client

def restart_and_reconnect():
  print('Failed to connect to MQTT broker. Reconnecting...')
  time.sleep(10)
  machine.reset()


wlan = network.WLAN(network.STA_IF)
wlan.active(True)
count = 1
while not wlan.isconnected():
    print('connection tries',count)
    wlan.connect(SSID, PW)
    time.sleep(1)
    count += 1
    
print('connected??', wlan.isconnected())
print('wlan status', wlan.status()) 
print( 'ip: ', wlan.ifconfig()[0] )

try:
  client = connect_and_subscribe()
except OSError as e:
  restart_and_reconnect()

while True:
  try:
    client.check_msg()
    if (time.time() - last_message) > message_interval:
      msg = b'Hello #%d' % counter
      client.publish(topic_pub, msg)
      last_message = time.time()
      counter += 1
  except OSError as e:
    restart_and_reconnect()

Well the arduino rp2040 are back in play again :)

[ScooterKraig]

I gave your last example a try but like my program, it works on the Raspberry but not on the Arduino. Arduino results:

MPY: soft reboot
connection tries 1
connection tries 2
connected?? True
wlan status True
ip:  192.168.1.190
Failed to connect to MQTT broker. Reconnecting...
Traceback (most recent call last):
  File "<stdin>", line 61, in <module>
NameError: name 'client' isn't defined

Odd that it also fails at Line 61: "client.check_msg()" with the Arduino and not with the Raspberry. I did take the machine.reset() out of "restart_and_reconnect():", or the whole machine would halt if it didn't connect to mqtt the first time.

Guess I'll keep trying with these Arduinos, though I think I could accomplish the same thing with a Raspberry Pico. This is just a home project to try to make my furnace "smarter". Thanks for your help!

[beetlegigg]

Very strange. To check I copied the code from my post and saved it to my nano with a new name and it worked OK.

I normally use the @peterhinch mqtt_as module for my mqtt client and I just checked to see if that works on the nano. A slight hitch was that Peter's code gets the platform which is 'rp2' for both the pico and nano and it then performs some nano incompatable tweaks at points in the code. I found the easy way to overcome this was to simply alter the line of code (about line 30) to override the platform to be 'nano' e.g.
#from sys import platform
platform = 'nano'
and then this excellent and robust mqtt client seem to run OK on the nano.

[peterhinch]

@beetlegigg I bought an early Arduino nano connect. Despite days of effort (including with help from @jimmo) I never managed to make it work with MicroPython. Consequently mqtt_as is untested on that platform.

If you would like to submit a PR I would be keen to accept it.

[beetlegigg]

@peterhinch
Thanks for the interest in a PR for making mqtt_as work with the Arduino nano connect. First up is to say whilst I think I understand a PR is a submission of amended code for approval, I've only been dabbling with programming and micropython since I retired, I've never been a real programmer and I'm not sure of the mechanism for submitting a PR.

The tweak I did to make mqtt_as work with the nano was simply to change the setting of the variable 'platform' from 'rp2' so that the RP2 = platform == "rp2" ends up as False thus the following code is not actioned.

elif RP2:
    BUSY_ERRORS = [EINPROGRESS, ETIMEDOUT, -110]

if RP2:  # Disable auto-sleep.
    # https://datasheets.raspberrypi.com/picow/connecting-to-the-internet-with-pico-w.pdf
    # para 3.6.3
    s.config(pm=0xA11140)	

elif RP2:  # 1 is STAT_CONNECTING. 2 reported by user (No IP?)
    if not 1 <= s.status() <= 2:
        break

I suppose that the #Disable auto-sleep and # 1 is STAT_CONNECTING would be specific to the wifi that the pico uses and certainly the nano objects to these. I'm not sure of the impact of ignoring the RP2 BUSY_ERRORS but note the default is then set to just
BUSY_ERRORS = [EINPROGRESS, ETIMEDOUT]

I did have a quick test and all seemed to work OK on the nano, but I've not used it in earnest.

As both the nano and pico both have the platform of 'rp2' I don't know how one could make the code work equally for the nano and the pico automatically. I just hacked the mqtt_as code as placed on the nano.

Firstly of course the nano's wifi must be made to work. Like you I have an early nano. When I first had the nano it immediately needed a firmware update to make the wifi work at all. (this is an Arduino firmware update, nothing to do with micropython firmware.) Back then, if I remember correctly, I had to update the Arduino firmware via an Arduino web link. Sometime later the wifi stopped working with micropython and updates via the Arduino web link no longer worked.

Recently, through a suggestion from @Josverl I found there was a firmware updater program called arduino-fwuploader. I download this to my mac computer along with the latest micropython for the nano from the mp download page. To upload this to the arduino board I had to use the following command:
./arduino-fwuploader firmware flash --fqbn arduino:mbed_nano:nanorp2040connect --address /dev/tty.usbmodem111101 -i NINA-arduino.mbed_nano.nanorp2040connect.bin

Rather than change the mqtt_as code I suggest it may be better to simply put a note in your docs about the use of the nano board should you see fit. Well at least I may have enabled you resuscitate your Arduino nano board which is probably languishing in a forgotten electronics bits drawer like mine was, though I'm not so sure you will make any good use of it :)

[beetlegigg]

You will also need to comment out as follows

                #elif RP2:  # 1 is STAT_CONNECTING. 2 reported by user (No IP?)
                #    if not 1 <= s.status() <= 2:
                #        break

to get it to work with the nano 2040 connect

[scruss]

The NINA firmware can be updated with espflash.py from micropython-lib. That maintains the rp2 flash content.

Is there any documentation for that? It would be really nice to have an easy way to update / check NINA firmware.

[robert-hh]

There is an example in the espflash directory.

[scruss]

not exactly user-friendly, though: the NINA firmware comes from? The user calculates the hash using? Also, some text to the effect of "This allows you to update your NINA firmware directly from MicroPython" might help people use it

[robert-hh]

As part of the attempt to support WiFi for MIMXRT and SAMD I had started instructions with espflash.py on how to build and install the firmware. That would as well provide the firmware versions. I stopped that, because maintaining that would not be worth the effort, but it's still there at https://github.com/robert-hh/micropython-lib/tree/nina_firmware. But even that does not mention building the hash using md5sum.

[peterhinch]

@scruss Following your suggestions I got to the point where "FIRMWARE-VERSION: 3.0.1" was displayed. I put the board into bootloader mode by powering up with REC and Gnd linked, and installed the latest release uf2 in the usual way. I now have a REPL.

However I have completely failed to connect to the WLAN. The following script (which runs on a Pico W) hangs at 'connecting to network...'

import network
import ubinascii
import machine
#    import network
sta_if = network.WLAN(network.STA_IF)
ap = network.WLAN(network.AP_IF) # create access-point interface
ap.active(False)         # deactivate the interface
if not sta_if.isconnected():
    print('connecting to network...')
    sta_if.active(True)
    sta_if.connect('misspiggy', 'redacted')
    while not sta_if.isconnected():
        pass
print('network config:', sta_if.ifconfig())
a = sta_if.config('mac')
print(f"MAC {a[0]:02x}:{a[1]:02x}:{a[2]:02x}:{a[3]:02x}:{a[4]:02x}:{a[5]:02x}", end="")
print(f'          b"\\x{a[0]:02X}\\x{a[1]:02X}\\x{a[2]:02X}\\x{a[3]:02X}\\x{a[4]:02X}\\x{a[5]:02X}"', end="")
print(f'          {ubinascii.hexlify(machine.unique_id())}')  # Verify that this is MAC

sta_if.scan() shows (b'misspiggy', b'\x00\x1d\xaa\x84$\xd0', 3, -63, 4, 1) among others, so it can see my network but I can't persuade it to connect to it.

The accursed thing is almost working... Any thoughts?

[scruss]

I wish I could say otherwise, @peterhinch, but your code does the thing for me:

connecting to network...
network config: ('192.168.2.128', '255.255.255.0', '192.168.2.1', '192.168.2.1')
MAC 14:91:82:2e:8b:50          b"\x14\x91\x82\x2E\x8B\x50"          b'501593006887891c'

scan returns (b'CB283W', b'\x14\x91\x82.\x8bP', 1, -53, 4, 1) amongst other things (including a MicroPython board in AP mode somewhere in the house that has been hiding from me for over a year).

[beetlegigg]

@peterhinch
I'm most probably not correctly interpreting your last post so just ignore my post if so, but from what I can see you have connected to the wifi. I put a very similar bit of connection code to yours in the script below, I get a similar response to xx.scan() but it then goes on to connect to my mqtt broker and can publish and subscribe ok. (using my modified mqtt_as.py)

import network
import time
import ubinascii

from mqtt_as import MQTTClient, config
import asyncio
from secrets import SSID, PW

wlan = network.WLAN(network.STA_IF)
wlan.active(True)
count = 1
while not wlan.isconnected():
    print('connection tries',count)
    wlan.connect(SSID, PW)
    time.sleep(1)
    count += 1

print('connected??', wlan.isconnected())
print('wlan status', wlan.status()) 
print( 'ip: ', wlan.ifconfig()[0] )

print('network config:', wlan.ifconfig())
a = wlan.config('mac')
print(f"MAC {a[0]:02x}:{a[1]:02x}:{a[2]:02x}:{a[3]:02x}:{a[4]:02x}:{a[5]:02x}", end="")
print(f'          b"\\x{a[0]:02X}\\x{a[1]:02X}\\x{a[2]:02X}\\x{a[3]:02X}\\x{a[4]:02X}\\x{a[5]:02X}"', end="")
print(f'          {ubinascii.hexlify(machine.unique_id())}')  # Verify that this is MAC

print(wlan.scan())

# ------------------------------------------------------

# mqtt server
#config['server'] = '10.0.1.37'  # Change to suit
config['server'] = '10.0.1.141'  # Change to suit

# WiFi
config['ssid'] = SSID
config['wifi_pw'] = PW


sensor = 23.5

# ------------------------------------------------------
def requested(payload):
    if payload == 'temperature':
        # publishing the response     
        asyncio.create_task(client.publish('test/RESPONSE', str(sensor)))   

#-----------------------------------------------------------
# MQTT
# mqtt message received callback
def sub_cb(topic, msg, retained):
    topics = topic.decode("utf-8")
    payload = msg.decode()
    if topics == 'test/request':
        requested(payload)
          
# mqtt connection subscriptions 
async def conn_han(client):
    #Subscribing to topics
    await client.subscribe('test/request')
 
#----------------------------------------------------------------
# main function 
async def main(client):
    try:
        print('trying to connect to MQTT broker')
        await client.connect()
        print('connected to MQTT broker')
    except OSError:
        print('MQTT connection failed.')
    
    while True:
        await client.publish('test/request', 'temperature')
        await asyncio.sleep(5)

#---------------------------------------------------------------
async def wifi_han(state):
    pass

# Define configuration for mqtt_as library
config['subs_cb'] = sub_cb
config['wifi_coro'] = wifi_han
config['connect_coro'] = conn_han
config['clean'] = True

# Set up client
MQTTClient.DEBUG = False  # Optional
client = MQTTClient(config)

try:
    asyncio.run(main(client))
finally:
    client.close() 
    asyncio.new_event_loop()

[beetlegigg]

I probably should have also put in the REPL responses for my previous post script :)
MPY: soft reboot
connection tries 1
connection tries 2
connected?? True
wlan status True
ip: 10.0.1.118
network config: ('10.0.1.118', '255.255.255.0', '10.0.1.1', '10.0.1.1')
MAC e0:28:6d:b6:f1:4e b"\xE0\x28\x6D\xB6\xF1\x4E" b'50157249489b9c1c'
[(b'FRITZ', b'\xe0(m\xb6\xf1N', 6, -46, 4, 1)]
trying to connect to MQTT broker
connected to MQTT broker

[peterhinch]

The difference between your script and mine is that you repeatedly issue wlan.connect(). When I run this code I see

connection tries 1
connection tries 2
# forever

with it never connecting. There is something wrong with my board or its setup...

[ScooterKraig]

If it's any help, I've tried your latest code with my Raspberry and with the Arduino. The Raspberry appears to work and does publish to the mqtt broker; the Arduino returns the following. I've redacted some of the wlan.scan stuff -- it finds my printer, and the neighbor's network! :)

MPY: soft reboot
connection tries 1
connection tries 2
connected?? True
wlan status True
ip:  192.168.1.190
network config: ('192.168.1.190', '255.255.255.0', '192.168.1.1', '192.168.1.1')
MAC 14:55:b9:0c:e6:5a          b"\x14\x55\xB9\x0C\xE6\x5A"          b'5034c60642598c18'
[(b'...my ssid....', .......more stuff here, deleted...then my printer...(b'DIRECT-eeCLX-3300 Series', 
....and the neighbor's ssid....]
trying to connect to MQTT broker
Traceback (most recent call last):
  File "<stdin>", line 93, in <module>
  File "asyncio/core.py", line 1, in run
  File "asyncio/core.py", line 1, in run_until_complete
  File "asyncio/core.py", line 1, in run_until_complete
  File "<stdin>", line 69, in main
  File "mqtt_as.py", line 778, in connect
  File "mqtt_as.py", line 739, in wifi_connect
ValueError: AP required

I have no idea what this means, it's just FYI if it helps.

Also, sometimes it doesn't connect and issues:

connection tries 1
connection tries 2
connection tries 3
connection tries 4

and so on. On a subsequent try, it connects on the second try.

[ScooterKraig]

By the way, don't spin your wheels on this for my sake. I can go back to the Raspberry Pico and set the Nano RP2040 aside for another project.

[peterhinch]

It turns out that my Arduino board actually works - it concealed this status by being remarkably insensitive. It connects reliably in the same room as the AP.

I've now been able to test with mqtt_as and have pushed an update. While I have not tested for resilience it publishes and responds correctly to incoming messages.

Thanks to @beetlegigg and @scruss who advised on arduino-fwuploader and @beetlegigg who correctly identified the necessary changes to the library.

[peterhinch]

-53dBm? My board would have no truck with that. See below.