Beetle ESP32 C3 蓝牙数据收发

esp32 dfrobot 单片机

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发布时间: 2022-09-13

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### 前言

ESP32 C3最大的特色就是wifi和蓝牙，wifi已经在前面几篇文章中进行了试用，今天来试用蓝牙功能。对于蓝牙，最基础的功能就是数据收发。因此，本篇将实现蓝牙数据的收发。

### 关键点说明

本篇蓝牙的Arduino程序参考了DFRobot官方文档，在这里只对关键点给出自己的理解并做出说明。

1. 要实现的功能

- 开发板通过蓝牙向外发送“Hello,www.icxbk.com”,发送间隔1s；
	- 开发板蓝牙接收到的消息通过uart打印出来；

2. 需要包含的头文件
	```c
	#include <BLEDevice.h>
	#include <BLEServer.h>
	#include <BLEUtils.h>
	#include <BLE2902.h>

```
	
3. 事件回调函数

蓝牙的连接和断开都会产生事件，在事件回调函数里指定需要做的事情。同样，蓝牙的数据接收也会产生对应的接收事件，在接收事件回调函数指定数据的处理方式。

代码在连接和断开回调函数中打印当前的连接状态，同时将状态记录下来。
	```c

//蓝牙连接/断开处理。当有连接/断开事件发生时自动触发
	class MyServerCallbacks: public BLEServerCallbacks {
		void onConnect(BLEServer* pServer) {   //当蓝牙连接时会执行该函数
		  Serial.println("蓝牙已连接");
		  deviceConnected = true;
		};

void onDisconnect(BLEServer* pServer) {  //当蓝牙断开连接时会执行该函数
		  Serial.println("蓝牙已断开");
		  deviceConnected = false;
		  delay(500); // give the bluetooth stack the chance to get things ready
		  pServer->startAdvertising(); // restart advertising

}
	};
	```

在接收回调函数中将接收到的数据通过uart串口打印出来。

```c
	//蓝牙接收数据处理。当收到数据时自动触发
	class MyCallbacks: public BLECharacteristicCallbacks {
		void onWrite(BLECharacteristic *pCharacteristic) {
		  std::string rxValue = pCharacteristic->getValue();//接收数据，并赋给rxValue

4. 主循环中进行数据的发送

```c
	void loop() {
	/@@****************数据发送部分*************/
	/@@****************************************/
	  if (deviceConnected) {  //如果有蓝牙连接，就发送数据
		pTxCharacteristic->setValue("Hello,www.icxbk.com");  //发送字符串
		pTxCharacteristic->notify();
		delay(1000); // bluetooth stack will go into congestion, if too many packets are sent
	  }
	/@@****************************************/
	/@@****************************************/
	}
	```

### 效果演示

手机使用BLE调试助手与开发板蓝牙连接。
连接上以后，uart会显示已连接：

![](https://cf05.ickimg.com/bbsimages/202209/ff04409bbc8a968e3364f04141ab7634.jpg)

手机上查看消息接收如下：
![](https://cf05.ickimg.com/bbsimages/202209/b6b83a22c72c8ef3b9ad547c336bdea0.png)

手机上发送消息，开发板会将消息通过uart打印出来：
![](https://cf05.ickimg.com/bbsimages/202209/5a9768b0dd2acae4b107598a384f3fff.png)

![](https://cf05.ickimg.com/bbsimages/202209/7ac34b5399415d02c8f406e5f2fdc255.jpg)

### 完整源代码

```c
/@@*
    Video: https://www.youtube.com/watch?v=oCMOYS71NIU
    Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleNotify.cpp
    Ported to Arduino ESP32 by Evandro Copercini

Create a BLE server that, once we receive a connection, will send periodic notifications.
   The service advertises itself as: 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
   Has a characteristic of: 6E400002-B5A3-F393-E0A9-E50E24DCCA9E - used for receiving data with "WRITE" 
   Has a characteristic of: 6E400003-B5A3-F393-E0A9-E50E24DCCA9E - used to send data with  "NOTIFY"

The design of creating the BLE server is:
   1. Create a BLE Server
   2. Create a BLE Service
   3. Create a BLE Characteristic on the Service
   4. Create a BLE Descriptor on the characteristic
   5. Start the service.
   6. Start advertising.

/@@* 该示例演示了蓝牙数据透传，烧录代码，打开串口监视器，打开手机的BLE调试助手
 * 1.即可看见ESP32-C3发送的数据
 * 2.通过BLE调试助手的输入框可向ESP32-C3发送数据
 */

#include <BLEDevice.h>
#include <BLEServer.h>
#include <BLEUtils.h>
#include <BLE2902.h>

BLEServer *pServer = NULL;
BLECharacteristic * pTxCharacteristic;
bool deviceConnected = false;
uint8_t txValue = 0;

// See the following for generating UUIDs:
// https://www.uuidgenerator.net/

#define SERVICE_UUID           "6E400001-B5A3-F393-E0A9-E50E24DCCA9E" // UART service UUID
#define CHARACTERISTIC_UUID_RX "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"
#define CHARACTERISTIC_UUID_TX "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"

//蓝牙连接/断开处理。当有连接/断开事件发生时自动触发
class MyServerCallbacks: public BLEServerCallbacks {
    void onConnect(BLEServer* pServer) {   //当蓝牙连接时会执行该函数
      Serial.println("蓝牙已连接");
      deviceConnected = true;
    };

void onDisconnect(BLEServer* pServer) {  //当蓝牙断开连接时会执行该函数
      Serial.println("蓝牙已断开");
      deviceConnected = false;
      delay(500); // give the bluetooth stack the chance to get things ready
      pServer->startAdvertising(); // restart advertising

}
};

/@@****************数据接收部分*************/
/@@****************************************/
//蓝牙接收数据处理。当收到数据时自动触发
class MyCallbacks: public BLECharacteristicCallbacks {
    void onWrite(BLECharacteristic *pCharacteristic) {
      std::string rxValue = pCharacteristic->getValue();//接收数据，并赋给rxValue

if (rxValue.length() > 0) {
        Serial.println("*********");
        Serial.print("Received Value: ");
        for (int i = 0; i < rxValue.length(); i++){
          Serial.print(rxValue[i]);
        }
        Serial.println();
        Serial.println("*********");
      }
    }
};
/@@***************************************/
/@@****************************************/

void setup() {
  Serial.begin(115200);
  BLEBegin();  //初始化蓝牙

}

void loop() {
/@@****************数据发送部分*************/
/@@****************************************/
  if (deviceConnected) {  //如果有蓝牙连接，就发送数据
    pTxCharacteristic->setValue("Hello,www.icxbk.com");  //发送字符串
    pTxCharacteristic->notify();
    delay(1000); // bluetooth stack will go into congestion, if too many packets are sent
  }
/@@****************************************/
/@@****************************************/
}

void BLEBegin(){
  // Create the BLE Device
  BLEDevice::init(/@@*BLE名称*/"UART Service");

// Create the BLE Server
  pServer = BLEDevice::createServer();
  pServer->setCallbacks(new MyServerCallbacks());

// Create the BLE Service
  BLEService *pService = pServer->createService(SERVICE_UUID);

// Create a BLE Characteristic
  pTxCharacteristic = pService->createCharacteristic(
                    CHARACTERISTIC_UUID_TX,
                    BLECharacteristic::PROPERTY_NOTIFY
                  );

pTxCharacteristic->addDescriptor(new BLE2902());

BLECharacteristic * pRxCharacteristic = pService->createCharacteristic(
                      CHARACTERISTIC_UUID_RX,
                      BLECharacteristic::PROPERTY_WRITE
                    );

pRxCharacteristic->setCallbacks(new MyCallbacks());

// Start the service
  pService->start();

// Start advertising
  pServer->getAdvertising()->start();
  Serial.println("Waiting a client connection to notify...");
}
```

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