BLE Not Stable on iOS/iPadOS/macOS

Official Hardware Nicla Family Nicla Voice
1

Hello,

I cannot get a stable BLE connection to Nicla Voice.
Trying with the example above in the Bluetooth communication section, connecting with iOS/iPadOS/macOS we always get the same anomalous behavior:
The connection is made and a few moments later (ranging from a few hundred ms up to a few seconds) the connection is closed by the board.
The app we use to test the connection is nrfConnect (but we also tried with our own swift iOS/macOS/iPadOS app that I could share for testing). NrfConnect stays in a spinning "Connecting" state.
On macOS I was able to connect only once after flashing, then after restart the app always this strange
behaviour.

This is the official example in the Bluetooth® Low Energy section.
https://docs.arduino.cc/tutorials/nicla-voice/user-manual/

#include "Nicla_System.h"
#include <ArduinoBLE.h>


// Define the voltage service and its characteristic
BLEService voltageService("1101");
BLEUnsignedCharCharacteristic voltageLevelChar("2101", BLERead | BLENotify);


const int analogPin = A0;


/**
 Read voltage level from an analog input of the Nicla Voice,
 then maps the voltage reading to a percentage value ranging from 0 to 100.


 @param none
 @return the voltage level percentage (int).
*/
int readVoltageLevel() {
 int voltage = analogRead(analogPin);
 int voltageLevel = map(voltage, 0, 1023, 0, 100);
 return voltageLevel;
}


void setup() {
 // Initialize the Nicla system and the built-in RGB LED
 nicla::begin();
 nicla::leds.begin();


 Serial.begin(9600);
 // Wait for the serial connection to be established
 while (!Serial)
   ;


 // Initialize the BLE module
 if (!BLE.begin()) {
   Serial.println("starting BLE failed!");
   while (1)
     ;
 }


 // Set the local name and advertised service for the BLE module
 BLE.setLocalName("VoltageMonitor");
 BLE.setAdvertisedService(voltageService);
 voltageService.addCharacteristic(voltageLevelChar);
 BLE.addService(voltageService);


 // Start advertising the BLE service
 BLE.advertise();
 Serial.println("- Bluetooth device active, waiting for connections...");
}


void loop() {
 // Check for incoming BLE connections
 BLEDevice central = BLE.central();


 // If a central device is connected
 if (central) {
   Serial.print("- Connected to central: ");
   Serial.println(central.address());


   // Turn off the LED when disconnected
   nicla::leds.setColor(blue);


   // While the central device is connected
   while (central.connected()) {
     // Read the voltage level and update the BLE characteristic with the level value
     int voltageLevel = readVoltageLevel();


     Serial.print("- Voltage level is: ");
     Serial.println(voltageLevel);
     voltageLevelChar.writeValue(voltageLevel);


     delay(200);
   }
 }


 // Turn off the LED when disconnected
 nicla::leds.setColor(red);


 Serial.print("- Disconnected from central: ");
 Serial.println(central.address());
}```

While trying to connect with NRFConnect the serial Nicla output is

- Voltage level is: 2

- Voltage level is: 0

- Disconnected from central: 4d:4e:61:02:52:89

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Connected to central: 4d:4e:61:02:52:89

- Voltage level is: 3

- Voltage level is: 3

- Voltage level is: 1

- Voltage level is: 0

- Voltage level is: 0

- Disconnected from central: 4d:4e:61:02:52:89

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Connected to central: 4d:4e:61:02:52:89

- Voltage level is: 0

- Voltage level is: 3

- Voltage level is: 4

- Voltage level is: 1

- Voltage level is: 0

- Disconnected from central: 4d:4e:61:02:52:89

- Disconnected from central: 00:00:00:00:00:00

- Disconnected from central: 00:00:00:00:00:00

- Connected to central: 4d:4e:61:02:5

Versions:

macOS: 15.4.1 (24E263)
iOS: 18.4.1
Arduino IDE: 15.4.1 (24E263)
CLI Version 1.2.0
ArduinoBLE: 1.4.0
Core: Arduino Mbed OS Nicla Boards 4.2.4

Steps to reproduce:

Behaviour:

  • nrfConnect will stay in a spinning "Connecting" state
  • if you open the serial monitor on Arduino IDE you will notice the board printing continuously
    Connected to central:
    some voltage values
    Disconnected from

Without having a really stable and working connection.