Arduino BLE data transmission

I am super new to programing and Arduino. Started playing with it about 6 months ago. I just purchased an Arduino 33 BLE Sense and an Arduino 33 IoT. My goal is to build a weather station of sorts with the BLE Sense and send the data to the IoT. Have had a few successful wireless builds between the two using other peoples projects then changing for fun or to match my available hardware. I am using the ArduinoBLE library. I have hit a stag in my learning. The ArduinoBLE library reference does not seem to explain a problem I am having. Using the ControlLED example (from the ArduinoBLE library) I have had great success sending other data other than on and off. Unfortunately I can not figure out how to send a number larger than 8 bits from the BLE Sense to the IoT. When I remove the “(byte)” from the writeValue and I hit verify I get this error message on the very line; “call of overloaded ‘writeValue(int)’ is ambiguous”

Why does this code not allow for more that 8 bit transmission? Why does it require “(byte)” to be used in the write.Value even if the value is 8 bits or smaller? Is there a change I can make to the code that will allow for a 12 bit number to be transmitted? In the BatteryMonitor example I am able to have larger numbers that 8 bit. What is the difference? I do know that 8 bits = 1 byte. Thank you for your time.

Below is original ControlLED code I keep trying to change.

  LED Control

  This example scans for BLE peripherals until one with the advertised service
  "19b10000-e8f2-537e-4f6c-d104768a1214" UUID is found. Once discovered and connected,
  it will remotely control the BLE Peripheral's LED, when the button is pressed or released.

  The circuit:
  - Arduino MKR WiFi 1010, Arduino Uno WiFi Rev2 board, Arduino Nano 33 IoT,
    Arduino Nano 33 BLE, or Arduino Nano 33 BLE Sense board.
  - Button with pull-up resistor connected to pin 2.

  You can use it with another board that is compatible with this library and the
  Peripherals -> LED example.

  This example code is in the public domain.

#include <ArduinoBLE.h>

// variables for button
const int buttonPin = 2;
int oldButtonState = LOW;

void setup() {
  while (!Serial);

  // configure the button pin as input
  pinMode(buttonPin, INPUT);

  // initialize the BLE hardware

  Serial.println("BLE Central - LED control");

  // start scanning for peripherals

void loop() {
  // check if a peripheral has been discovered
  BLEDevice peripheral = BLE.available();

  if (peripheral) {
    // discovered a peripheral, print out address, local name, and advertised service
    Serial.print("Found ");
    Serial.print(" '");
    Serial.print("' ");

    if (peripheral.localName() != "LED") {

    // stop scanning


    // peripheral disconnected, start scanning again

void controlLed(BLEDevice peripheral) {
  // connect to the peripheral
  Serial.println("Connecting ...");

  if (peripheral.connect()) {
  } else {
    Serial.println("Failed to connect!");

  // discover peripheral attributes
  Serial.println("Discovering attributes ...");
  if (peripheral.discoverAttributes()) {
    Serial.println("Attributes discovered");
  } else {
    Serial.println("Attribute discovery failed!");

  // retrieve the LED characteristic
  BLECharacteristic ledCharacteristic = peripheral.characteristic("19b10001-e8f2-537e-4f6c-d104768a1214");

  if (!ledCharacteristic) {
    Serial.println("Peripheral does not have LED characteristic!");
  } else if (!ledCharacteristic.canWrite()) {
    Serial.println("Peripheral does not have a writable LED characteristic!");

  while (peripheral.connected()) {
    // while the peripheral is connected

    // read the button pin
    int buttonState = digitalRead(buttonPin);

    if (oldButtonState != buttonState) {
      // button changed
      oldButtonState = buttonState;

      if (buttonState) {
        Serial.println("button pressed");

        // button is pressed, write 0x01 to turn the LED on
      } else {
        Serial.println("button released");

        // button is released, write 0x00 to turn the LED off

  Serial.println("Peripheral disconnected");

Original BatteryMonitor code

  Battery Monitor

  This example creates a BLE peripheral with the standard battery service and
  level characteristic. The A0 pin is used to calculate the battery level.

  The circuit:
  - Arduino MKR WiFi 1010, Arduino Uno WiFi Rev2 board, Arduino Nano 33 IoT,
    Arduino Nano 33 BLE, or Arduino Nano 33 BLE Sense board.

  You can use a generic BLE central app, like LightBlue (iOS and Android) or
  nRF Connect (Android), to interact with the services and characteristics
  created in this sketch.

  This example code is in the public domain.

#include <ArduinoBLE.h>

 // BLE Battery Service
BLEService batteryService("180F");

// BLE Battery Level Characteristic
BLEUnsignedCharCharacteristic batteryLevelChar("2A19",  // standard 16-bit characteristic UUID
    BLERead | BLENotify); // remote clients will be able to get notifications if this characteristic changes

int oldBatteryLevel = 0;  // last battery level reading from analog input
long previousMillis = 0;  // last time the battery level was checked, in ms

void setup() {
  Serial.begin(9600);    // initialize serial communication
  while (!Serial);

  pinMode(LED_BUILTIN, OUTPUT); // initialize the built-in LED pin to indicate when a central is connected

  // begin initialization
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");

    while (1);

  /* Set a local name for the BLE device
     This name will appear in advertising packets
     and can be used by remote devices to identify this BLE device
     The name can be changed but maybe be truncated based on space left in advertisement packet
  BLE.setAdvertisedService(batteryService); // add the service UUID
  batteryService.addCharacteristic(batteryLevelChar); // add the battery level characteristic
  BLE.addService(batteryService); // Add the battery service
  batteryLevelChar.writeValue(oldBatteryLevel); // set initial value for this characteristic

  /* Start advertising BLE.  It will start continuously transmitting BLE
     advertising packets and will be visible to remote BLE central devices
     until it receives a new connection */

  // start advertising

  Serial.println("Bluetooth device active, waiting for connections...");

void loop() {
  // wait for a BLE central
  BLEDevice central = BLE.central();

  // if a central is connected to the peripheral:
  if (central) {
    Serial.print("Connected to central: ");
    // print the central's BT address:
    // turn on the LED to indicate the connection:
    digitalWrite(LED_BUILTIN, HIGH);

    // check the battery level every 200ms
    // while the central is connected:
    while (central.connected()) {
      long currentMillis = millis();
      // if 200ms have passed, check the battery level:
      if (currentMillis - previousMillis >= 200) {
        previousMillis = currentMillis;
    // when the central disconnects, turn off the LED:
    digitalWrite(LED_BUILTIN, LOW);
    Serial.print("Disconnected from central: ");

void updateBatteryLevel() {
  /* Read the current voltage level on the A0 analog input pin.
     This is used here to simulate the charge level of a battery.
  int battery = analogRead(A0);
  int batteryLevel = map(battery, 0, 1023, 0, 100);

  if (batteryLevel != oldBatteryLevel) {      // if the battery level has changed
    Serial.print("Battery Level % is now: "); // print it
    batteryLevelChar.writeValue(batteryLevel);  // and update the battery level characteristic
    oldBatteryLevel = batteryLevel;           // save the level for next comparison

Maybe it has something to do with it being a central and not periferal device. I'm pretty new to the ble as well so thats just a guess.

Last time I read up the the word byte in the library I did not really understand it's definition, and in some ways I still don't full understand it's purpose. However, clicking around and reading other definitions I found "short" and "long". I had read the definitions in the past as well, yet nothing had clicked. Last night I realized they are similar to "byte" only can hold larger numbers. So I replaced "byte" with "short" and that fixed the problem. I can now transmit up to 16 bit size numbers. I will add to look out for replacing the word byte in both codes the central and peripheral.

snapppdogg, thanks for posting this code. It will (I think) help me with a project I’m working on. But I have been unable to find ArdinoBLE.h anywhere. Can you tell me where you found it??


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