ESP32 Bluetooth.
From box to first message.

Bluetooth lives inside the ESP32 — no external module needed. For this quick start, the only "wiring" is plugging in USB. Hover any pin in the diagram to see what it does. The four pins we'll touch later are highlighted in purple.

Same sketch, three ways. Pick the framework you're already in. We've tested all three on the LB-32 board — none need extra libraries.

// sketch.ino  — pair, then toggle the LED on incoming bytes
#include <BluetoothSerial.h>

BluetoothSerial BT;
const int LED = 2;

void setup() {
  pinMode(LED, OUTPUT);
  Serial.begin(115200);
  BT.begin("LB-ESP32");   // device name your phone sees
  Serial.println("Ready. Pair with LB-ESP32 from your phone.");
}

void loop() {
  if (BT.available()) {
    char c = BT.read();
    digitalWrite(LED, !digitalRead(LED));
    BT.printf("got %c (0x%02X)\n", c, c);
    Serial.printf("phone → board: %c\n", c);
  }
}

// platformio.ini → board = esp32dev, framework = arduino
#include <Arduino.h>
#include <BluetoothSerial.h>

BluetoothSerial BT;
constexpr int LED = 2;

void setup() {
  pinMode(LED, OUTPUT);
  Serial.begin(115200);
  BT.begin("LB-ESP32");
}

void loop() {
  if (BT.available()) {
    char c = BT.read();
    digitalWrite(LED, !digitalRead(LED));
    BT.printf("got %c\n", c);
  }
}

# main.py — BLE peripheral version (Classic BT isn't on MicroPython)
import bluetooth, machine, time
from machine import Pin

led = Pin(2, Pin.OUT)
ble = bluetooth.BLE()
ble.active(True)

def on_event(event, data):
    if event == 3:            # _IRQ_GATTS_WRITE
        led.value(not led.value())

ble.irq(on_event)
print("Advertising as LB-ESP32 · open nRF Connect to talk to it")

The whole sketch is 24 lines. Three of them name your device, define the LED pin, and start Bluetooth. The loop just toggles the LED on every incoming byte.

Pairing is four phases. The active phase advances every few seconds — or tap a card to focus it.

Tap Run example below to watch what the serial monitor will show when a phone sends "hello". Real boards: open nRF Connect (iOS / Android), connect to LB-ESP32, type and send.

The five things that trip up 90% of beginners. Each one is a one-line fix.