Bluetooth Usage
Seeed Studio XIAO ESP32C3 supports Bluetooth 5 (LE) connectivity. This wiki will introduce the basics of Bluetooth usage on this board.
Hardware set up
- Step 1. Connect the included WiFi/ Bluetooth antenna to the IPEX connector on the board

- Step 2. Connect XIAO ESP32C3 to your computer via a USB Type-C cable

Scan Bluetooth devices
In this example, we are going to use XIAO ESP32C3 to scan available Bluetooth devices around it.
- Step 1. Copy and paste the code below into Arduino IDE
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEScan.h>
#include <BLEAdvertisedDevice.h>
int scanTime = 5; //In seconds
BLEScan* pBLEScan;
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
void onResult(BLEAdvertisedDevice advertisedDevice) {
Serial.printf("Advertised Device: %s \n", advertisedDevice.toString().c_str());
}
};
void setup() {
Serial.begin(115200);
Serial.println("Scanning...");
BLEDevice::init("");
pBLEScan = BLEDevice::getScan(); //create new scan
pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
pBLEScan->setActiveScan(true); //active scan uses more power, but get results faster
pBLEScan->setInterval(100);
pBLEScan->setWindow(99); // less or equal setInterval value
}
void loop() {
// put your main code here, to run repeatedly:
BLEScanResults foundDevices = pBLEScan->start(scanTime, false);
Serial.print("Devices found: ");
Serial.println(foundDevices.getCount());
Serial.println("Scan done!");
pBLEScan->clearResults(); // delete results fromBLEScan buffer to release memory
delay(2000);
}
If you have already upgrade your ESP32 development board to version 3.0.0 above, you need to change some code to compatible with it.
BLEScanResults foundDevices = pBLEScan->start(scanTime, false);
change toBLEScanResults* foundDevices = pBLEScan->start(scanTime, false);
Serial.println(foundDevices.getCount());
change toSerial.println(foundDevices->getCount());
Step 2. Upload the codes and open the Serial Monitor to start scanning for Bluetooth devices

XIAO ESP32C3 as Bluetooth server
In this example, we are going to use XIAO ESP32C3 as a Bluetooth server. Here we will search for XIAO ESP32C3 board using a smartphone and send out strings to display on the serial monitor
- Step 1. Copy and paste the code below into Arduino IDE
#include <BLEDevice.h>
#include <BLEUtils.h>
#include <BLEServer.h>
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
#define SERVICE_UUID "4fafc201-1fb5-459e-8fcc-c5c9c331914b"
#define CHARACTERISTIC_UUID "beb5483e-36e1-4688-b7f5-ea07361b26a8"
class MyCallbacks: public BLECharacteristicCallbacks {
void onWrite(BLECharacteristic *pCharacteristic) {
std::string value = pCharacteristic->getValue();
if (value.length() > 0) {
Serial.println("*********");
Serial.print("New value: ");
for (int i = 0; i < value.length(); i++)
Serial.print(value[i]);
Serial.println();
Serial.println("*********");
}
}
};
void setup() {
Serial.begin(115200);
BLEDevice::init("MyESP32");
BLEServer *pServer = BLEDevice::createServer();
BLEService *pService = pServer->createService(SERVICE_UUID);
BLECharacteristic *pCharacteristic = pService->createCharacteristic(
CHARACTERISTIC_UUID,
BLECharacteristic::PROPERTY_READ |
BLECharacteristic::PROPERTY_WRITE
);
pCharacteristic->setCallbacks(new MyCallbacks());
pCharacteristic->setValue("Hello World");
pService->start();
BLEAdvertising *pAdvertising = pServer->getAdvertising();
pAdvertising->start();
}
void loop() {
// put your main code here, to run repeatedly:
delay(2000);
}
If you have already upgrade your ESP32 development board to version 3.0.0 above, you need to change some code to compatible with it.
std::string value = pCharacteristic->getValue();
change toString value = pCharacteristic->getValue();
Step 2. Upload the codes and open the Serial Monitor
Step 3. Download and install LightBlue App on your smartphone
- Step 4. Open Bluetooth on your phone, bring the phone close to XIAO ESP32C3, scan for devices and connect with MyESP32 device

- Step 5. Open the LightBlue app and click Bonded tab

- Step 6. Click CONNECT next to MyESP32

- Step 7. Click the section at the very bottom which says Readable, Writable

- Step 8. Under Data format drop-down menu, select UTF-8 String

- Step 9. Type "Hello" under WRITTEN VALUES and click WRITE
You will see the text string "Hello" output on the serial monitor of Arduino IDE

NimBLE-Arduino
Introduction
This library significantly reduces resource usage and improves performance for ESP32 BLE applications as compared with the bluedroid based library. The goal is to maintain, as much as reasonable, compatibility with the original library but but using the NimBLE stack. In addition, this library will be more actively developed and maintained to provide improved capabilities and stability over the original.
For more information you can go to this author's Github link.
Step 1.Add Library

Step 2.Example
Code
#include <Arduino.h>
#include <NimBLEDevice.h>
#include <NimBLEAdvertisedDevice.h>
#include "NimBLEEddystoneTLM.h"
#include "NimBLEBeacon.h"
#define ENDIAN_CHANGE_U16(x) ((((x) & 0xFF00) >> 8) + (((x) & 0xFF) << 8))
int scanTime = 5 * 1000; // In milliseconds
NimBLEScan* pBLEScan;
class ScanCallbacks : public NimBLEScanCallbacks {
void onResult(const NimBLEAdvertisedDevice* advertisedDevice) override {
if (advertisedDevice->haveName()) {
Serial.print("Device name: ");
Serial.println(advertisedDevice->getName().c_str());
Serial.println("");
}
if (advertisedDevice->haveServiceUUID()) {
NimBLEUUID devUUID = advertisedDevice->getServiceUUID();
Serial.print("Found ServiceUUID: ");
Serial.println(devUUID.toString().c_str());
Serial.println("");
} else if (advertisedDevice->haveManufacturerData() == true) {
std::string strManufacturerData = advertisedDevice->getManufacturerData();
if (strManufacturerData.length() == 25 && strManufacturerData[0] == 0x4C && strManufacturerData[1] == 0x00) {
Serial.println("Found an iBeacon!");
NimBLEBeacon oBeacon = NimBLEBeacon();
oBeacon.setData(reinterpret_cast<const uint8_t*>(strManufacturerData.data()), strManufacturerData.length());
Serial.printf("iBeacon Frame\n");
Serial.printf("ID: %04X Major: %d Minor: %d UUID: %s Power: %d\n",
oBeacon.getManufacturerId(),
ENDIAN_CHANGE_U16(oBeacon.getMajor()),
ENDIAN_CHANGE_U16(oBeacon.getMinor()),
oBeacon.getProximityUUID().toString().c_str(),
oBeacon.getSignalPower());
} else {
Serial.println("Found another manufacturers beacon!");
Serial.printf("strManufacturerData: %d ", strManufacturerData.length());
for (int i = 0; i < strManufacturerData.length(); i++) {
Serial.printf("[%X]", strManufacturerData[i]);
}
Serial.printf("\n");
}
return;
}
NimBLEUUID eddyUUID = (uint16_t)0xfeaa;
if (advertisedDevice->getServiceUUID().equals(eddyUUID)) {
std::string serviceData = advertisedDevice->getServiceData(eddyUUID);
if (serviceData[0] == 0x20) {
Serial.println("Found an EddystoneTLM beacon!");
NimBLEEddystoneTLM foundEddyTLM = NimBLEEddystoneTLM();
foundEddyTLM.setData(reinterpret_cast<const uint8_t*>(serviceData.data()), serviceData.length());
Serial.printf("Reported battery voltage: %dmV\n", foundEddyTLM.getVolt());
Serial.printf("Reported temperature from TLM class: %.2fC\n", (double)foundEddyTLM.getTemp());
int temp = (int)serviceData[5] + (int)(serviceData[4] << 8);
float calcTemp = temp / 256.0f;
Serial.printf("Reported temperature from data: %.2fC\n", calcTemp);
Serial.printf("Reported advertise count: %d\n", foundEddyTLM.getCount());
Serial.printf("Reported time since last reboot: %ds\n", foundEddyTLM.getTime());
Serial.println("\n");
Serial.print(foundEddyTLM.toString().c_str());
Serial.println("\n");
}
}
}
} scanCallbacks;
void setup() {
Serial.begin(115200);
Serial.println("Scanning...");
NimBLEDevice::init("Beacon-scanner");
pBLEScan = BLEDevice::getScan();
pBLEScan->setScanCallbacks(&scanCallbacks);
pBLEScan->setActiveScan(true);
pBLEScan->setInterval(100);
pBLEScan->setWindow(100);
}
void loop() {
NimBLEScanResults foundDevices = pBLEScan->getResults(scanTime, false);
Serial.print("Devices found: ");
Serial.println(foundDevices.getCount());
Serial.println("Scan done!");
pBLEScan->clearResults(); // delete results scan buffer to release memory
delay(2000);
}
Result

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