How to send a text from an esp32 to app inventor?

sto programmando un programma antincendio che al rilevamento di fumo fa partire le ventole e invia un messaggio ad app inventor in modo da far uscire l avviso sul applicazione.


#include "BluetoothSerial.h"  

#define USE_PIN // Uncomment this to use PIN during pairing. The pin is specified on the line below
const char *pin = "1234"; // Change this to more secure PIN.

String device_name = "ESP32-BT-Slave";

#error Bluetooth is not enabled! Please run `make menuconfig` to and enable it

#error Serial Bluetooth not available or not enabled. It is only available for the ESP32 chip.

BluetoothSerial BT;

#define smokeSensorPin 34 // Pin analogico per il sensore di fumo MQ-2
const int buzzerPin = 5;       // Pin per il buzzer
const int ledPin = 13;          // Pin per il LED
const int fanInAPin = 14;      // Pin per l'ingresso inA del ponte H
const int fanInBPin = 27;      // Pin per l'ingresso inB del ponte H

void setup() {
  BT.begin(device_name); //Bluetooth device name
  Serial.printf("The device with name \"%s\" is started.\nNow you can pair it with Bluetooth!\n", device_name.c_str());
  #ifdef USE_PIN
    Serial.println("Using PIN");
  pinMode(buzzerPin, OUTPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(fanInAPin, OUTPUT);
  pinMode(fanInBPin, OUTPUT);


void loop() {
  // Leggi il valore dal sensore di fumo
  int smokeLevel = analogRead(smokeSensorPin);
  // Stampa il valore letto sulla porta seriale
  Serial.print("Livello di fumo: ");
  // Se il livello di fumo è superiore alla soglia, attiva il buzzer, accendi il LED e fai girare la ventola in una direzione
  if (smokeLevel > 1000) {
    digitalWrite(buzzerPin, HIGH);
    digitalWrite(ledPin, HIGH);
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
    // Attiva la ventola in una direzione
    digitalWrite(fanInAPin, HIGH);
    digitalWrite(fanInBPin, LOW);
    while (BT.available()){
     Serial.write("fumo rilevato");
  else {
    digitalWrite(buzzerPin, LOW);
    digitalWrite(ledPin, LOW);
    // Spegni la ventola
    digitalWrite(fanInAPin, LOW);
    digitalWrite(fanInBPin, LOW);
         while (BT.available()){
     Serial.write("fumo NON rilevato");
  // Aggiorna ogni secondo


I have a problem with app inventor, I've searched everywhere but I haven't found any tutorials on how to send a text from an esp32 to app inventor, can anyone help me?

Is the ESP32 using BLE?

here are the other FAQs


is a esp32 dev kit 1 i want to connect it whit classic bluetooth

i haven’t understood

Here are some tips by @ABG

Be sure to use println() at the end of each message to send from the sending device, to signal end of message.

Only use print() in the middle of a message.

Be sure not to println() in the middle of a message, or you will break it into two short messages and mess up the item count after you split the message in AI2.

Do not rely on timing for this, which is unreliable.

In the AI2 Designer, set the Delimiter attribute of the BlueTooth Client component to 10 to recognize the End of Line character.
Also, return data is not immediately available after sending a request,
you have to start a Clock Timer repeating and watch for its arrival in the Clock Timer event. The repeat rate of the Clock Timer should be faster than the transmission rate in the sending device, to not flood the AI2 buffers.

In your Clock Timer, you should check

  Is the BlueTooth Client still Connected?
  Is Bytes Available > 0?
     IF Bytes Available > 0 THEN
       set message var  to BT.ReceiveText(-1) 

This takes advantage of a special case in the ReceiveText block:

Receive text from the connected Bluetooth device. If numberOfBytes is less than 0, read until a delimiter byte value is received.

If you are sending multiple data values per message separated by | or comma, have your message split into a local or global variable for inspection before trying to select list items from it. Test if (length of list(split list result) >= expected list length) before doing any select list item operations, to avoid taking a long walk on a short pier. This bulletproofing is necessary in case your sending device sneaks in some commentary messages with the data values.

Some people send temperature and humidity in separate messages with distinctive prefixes like "t:" (for temperature) and "h:" (for humidity).
(That's YAML format.)

The AI2 Charts component can recognize these and graph them. See Bluetooth Client Polling Rate - #12 by ABG

To receive YAML format messages, test if the incoming message contains ':' . If true, split it at ':' into a list variable, and find the prefix in item 1 and the value in item 2.

thanks, but in the arduino code what I have to put to send message to app inventor ?

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