FREE SIMULATOR EXAMPLE · INTERMEDIATE

Raspberry Pi Pico 2 W ThingsBoard IoT

This example publishes telemetry from the Raspberry Pi Pico 2 W to ThingsBoard over MQTT — sensor readings become dashboard charts on the open-source IoT platform. The device-to-platform pattern.

Board	Raspberry Pi Pico W (RP2040 + WiFi)
Difficulty	intermediate
Category	communication
Libraries	None — just the Arduino core
Runs in	Sensbench browser simulator — free, no account

The exact circuit you get when you open this example — already wired, ready to run.

The sketch

# main.py
import network
import time
import json
import dht
from machine import Pin
from umqttsimple import MQTTClient

# --- Configuration ---
WIFI_SSID = "SENSBENCH-GUEST"   # SENSBENCH simulator's built-in WiFi network
WIFI_PASSWORD = ""           # the simulator AP is open
THINGSBOARD_HOST = "eu.thingsboard.cloud"
ACCESS_TOKEN = "tokenn"      # replace with YOUR ThingsBoard device token

# --- Hardware Setup ---
# Using "LED" for Pico W onboard LED, or Pin(15) for an external LED
led = Pin("LED", Pin.OUT) 
sensor = dht.DHT11(Pin(4)) 
led_state = False

# --- MQTT Callback (Handles Switch Commands) ---
def on_message(topic, msg):
    global led_state
    print(f"\n[RPC] Message received: {msg}")
    
    try:
        data = json.loads(msg)
        method = data.get("method")
        params = data.get("params")

        # Handling 'setState' from your ThingsBoard Switch
        if method == "setState":
            # This check ensures both boolean and string 'true' work
            if params is True or params == "true" or params == 1:
                led_state = True
                led.value(1)
            else:
                led_state = False
                led.value(0)
            
            print(f"Action: LED is now {'ON' if led_state else 'OFF'}")
            
        # Handling 'getState' to sync the dashboard switch
        elif method == "getState":
            request_id = topic.decode().split('/')[-1]
            client.publish(f"v1/devices/me/rpc/response/{request_id}", json.dumps(led_state))
            print("Action: Synced state with Dashboard")

    except Exception as e:
        print(f"RPC Error: {e}")

# --- Connection Functions ---
def connect_wifi():
    sta_if = network.WLAN(network.STA_IF)
    sta_if.active(True)
    sta_if.connect(WIFI_SSID, WIFI_PASSWORD)
    print("Connecting to WiFi", end="")
    while not sta_if.isconnected():
        print(".", end="")
        time.sleep(0.5)
    print(f"\nConnected! IP: {sta_if.ifconfig()[0]}")

def connect_mqtt():
    client = MQTTClient("Pico_W_Cuttack", THINGSBOARD_HOST, user=ACCESS_TOKEN, password="")
    client.set_callback(on_message)
    client.connect()
    client.subscribe(b"v1/devices/me/rpc/request/+")
    print("Connected to ThingsBoard MQTT!")
    return client

# --- Main Logic ---
connect_wifi()
client = connect_mqtt()

last_telemetry = 0

print("System Ready. Waiting for commands...")

while True:
    try:
        # Check for incoming RPC (Switch) messages
        client.check_msg() 

        # Send Telemetry every 10 seconds (standard for cloud stability)
        if (time.time() - last_telemetry) > 10:
            sensor.measure()
            t = sensor.temperature()
            h = sensor.humidity()
            
            payload = json.dumps({
                "temperature": t, 
                "humidity": h, 
                "ledStatus": led_state
            })
            
            client.publish("v1/devices/me/telemetry", payload)
            print(f"Published: {payload}")
            last_telemetry = time.time()

    except Exception as e:
        print(f"Error in Loop: {e}")
        time.sleep(5)
        import machine
        machine.reset() 


# umqttsimple.py
try:
    import usocket as socket
except:
    import socket
import ustruct as struct
from ubinascii import hexlify

class MQTTException(Exception):
    pass

class MQTTClient:

    def __init__(self, client_id, server, port=0, user=None, password=None, keepalive=0,
                 ssl=False, ssl_params={}):
        if port == 0:
            port = 8883 if ssl else 1883
        self.client_id = client_id
        self.sock = None
        self.server = server
        self.port = port
        self.ssl = ssl
        self.ssl_params = ssl_params
        self.pid = 0
        self.cb = None
        self.user = user
        self.pswd = password
        self.keepalive = keepalive
        self.lw_topic = None
        self.lw_msg = None
        self.lw_qos = 0
        self.lw_retain = False

    def _send_str(self, s):
        self.sock.write(struct.pack("!H", len(s)))
        self.sock.write(s)

    def _recv_len(self):
        n = 0
        sh = 0
        while 1:
            b = self.sock.read(1)[0]
            n |= (b & 0x7f) << sh
            if not b & 0x80:
                return n
            sh += 7

    def set_callback(self, f):
        self.cb = f

    def set_last_will(self, topic, msg, retain=False, qos=0):
        assert 0 <= qos <= 2
        assert topic
        self.lw_topic = topic
        self.lw_msg = msg
        self.lw_qos = qos
        self.lw_retain = retain

    def connect(self, clean_session=True):
        self.sock = socket.socket()
        addr = socket.getaddrinfo(self.server, self.port)[0][-1]
        self.sock.connect(addr)
        if self.ssl:
            import ussl
            self.sock = ussl.wrap_socket(self.sock, **self.ssl_params)
        premsg = bytearray(b"\x10\0\0\0\0\0")
        msg = bytearray(b"\x04MQTT\x04\x02\0\0")

        sz = 10 + 2 + len(self.client_id)
        msg[6] = clean_session << 1
        if self.user is not None:
            sz += 2 + len(self.user) + 2 + len(self.pswd)
            msg[6] |= 0xC0
        if self.keepalive:
            assert self.keepalive < 65536
            msg[7] |= self.keepalive >> 8
            msg[8] |= self.keepalive & 0x00FF
        if self.lw_topic:
            sz += 2 + len(self.lw_topic) + 2 + len(self.lw_msg)
            msg[6] |= 0x4 | (self.lw_qos & 0x1) << 3 | (self.lw_qos & 0x2) << 3
            msg[6] |= self.lw_retain << 5

        i = 1
        while sz > 0x7f:
            premsg[i] = (sz & 0x7f) | 0x80
            sz >>= 7
            i += 1
        premsg[i] = sz

        self.sock.write(premsg, i + 2)
        self.sock.write(msg)
        #print(hex(len(msg)), hexlify(msg, ":"))
        self._send_str(self.client_id)
        if self.lw_topic:
            self._send_str(self.lw_topic)
            self._send_str(self.lw_msg)
        if self.user is not None:
            self._send_str(self.user)
            self._send_str(self.pswd)
        resp = self.sock.read(4)
        assert resp[0] == 0x20 and resp[1] == 0x02
        if resp[3] != 0:
            raise MQTTException(resp[3])
        return resp[2] & 1

    def disconnect(self):
        self.sock.write(b"\xe0\0")
        self.sock.close()

    def ping(self):
        self.sock.write(b"\xc0\0")

    def publish(self, topic, msg, retain=False, qos=0):
        pkt = bytearray(b"\x30\0\0\0")
        pkt[0] |= qos << 1 | retain
        sz = 2 + len(topic) + len(msg)
        if qos > 0:
            sz += 2
        assert sz < 2097152
        i = 1
        while sz > 0x7f:
            pkt[i] = (sz & 0x7f) | 0x80
            sz >>= 7
            i += 1
        pkt[i] = sz
        #print(hex(len(pkt)), hexlify(pkt, ":"))
        self.sock.write(pkt, i + 1)
        self._send_str(topic)
        if qos > 0:
            self.pid += 1
            pid = self.pid
            struct.pack_into("!H", pkt, 0, pid)
            self.sock.write(pkt, 2)
        self.sock.write(msg)
        if qos == 1:
            while 1:
                op = self.wait_msg()
                if op == 0x40:
                    sz = self.sock.read(1)
                    assert sz == b"\x02"
                    rcv_pid = self.sock.read(2)
                    rcv_pid = rcv_pid[0] << 8 | rcv_pid[1]
                    if pid == rcv_pid:
                        return
        elif qos == 2:
            assert 0

    def subscribe(self, topic, qos=0):
        assert self.cb is not None, "Subscribe callback is not set"
        pkt = bytearray(b"\x82\0\0\0")
        self.pid += 1
        struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid)
        #print(hex(len(pkt)), hexlify(pkt, ":"))
        self.sock.write(pkt)
        self._send_str(topic)
        self.sock.write(qos.to_bytes(1, "little"))
        while 1:
            op = self.wait_msg()
            if op == 0x90:
                resp = self.sock.read(4)
                #print(resp)
                assert resp[1] == pkt[2] and resp[2] == pkt[3]
                if resp[3] == 0x80:
                    raise MQTTException(resp[3])
                return

    # Wait for a single incoming MQTT message and process it.
    # Subscribed messages are delivered to a callback previously
    # set by .set_callback() method. Other (internal) MQTT
    # messages processed internally.
    def wait_msg(self):
        res = self.sock.read(1)
        self.sock.setblocking(True)
        if res is None:
            return None
        if res == b"":
            raise OSError(-1)
        if res == b"\xd0":  # PINGRESP
            sz = self.sock.read(1)[0]
            assert sz == 0
            return None
        op = res[0]
        if op & 0xf0 != 0x30:
            return op
        sz = self._recv_len()
        topic_len = self.sock.read(2)
        topic_len = (topic_len[0] << 8) | topic_len[1]
        topic = self.sock.read(topic_len)
        sz -= topic_len + 2
        if op & 6:
            pid = self.sock.read(2)
            pid = pid[0] << 8 | pid[1]
            sz -= 2
        msg = self.sock.read(sz)
        self.cb(topic, msg)
        if op & 6 == 2:
            pkt = bytearray(b"\x40\x02\0\0")
            struct.pack_into("!H", pkt, 2, pid)
            self.sock.write(pkt)
        elif op & 6 == 4:
            assert 0

    # Checks whether a pending message from server is available.
    # If not, returns immediately with None. Otherwise, does
    # the same processing as wait_msg.
    def check_msg(self):
        self.sock.setblocking(False)
        return self.wait_msg()

How it works

The firmware connects to WiFi, authenticates with ThingsBoard over MQTT using a device access token, and publishes telemetry — sensor readings wrapped in JSON — on a schedule. The payload structure maps directly to the dashboard’s data keys.

The MQTT client loop keeps the connection alive between publishes, and the JSON payload is the contract: each key in the published object becomes a chartable field on the platform. The code’s job is measurement plus formatting; the platform does the rest.

Before you build it for real

Get the parts

Related examples

FAQ

What is ThingsBoard?

An open-source IoT platform: devices publish telemetry, and the platform stores, visualizes and rules on it. Compared to Blynk’s app-first approach, ThingsBoard is dashboard-first — charts, tables and alarms built around device data streams.

How does the Pico 2 W talk to it?

Over MQTT with an access token: the device connects to the ThingsBoard broker, authenticates with its token, and publishes JSON payloads to its telemetry topic. The platform then turns the JSON fields into dashboard widgets.