尝试使用 ESP32 的 BLE 功能和 Arduino IDE 为整数赋值的问题

Question

我是一名学生，目前正在攻读工程学位项目。我在编码、数据分析等方面有一些很好的基础知识，但我开始摸不着头脑了。所以基本上我一直在阅读 Arduino IDE 中包含的名为“BLE_write”的示例，该示例位于 ESP32 BLE Arduino 下的 ESP32 教程中。我将包括整个代码。这只是我整个项目的一部分，但它是让它发挥作用的关键一步。因此，本质上，此示例代码从手机上的应用程序中获取 uft-8 中的串行蓝牙，并将其打印到使用 ESP32 作为服务器的 PC 上的串行端口监视器上。 我需要做什么只是从蓝牙串口中取一个 1-60 的数字并将其分配给一个 int 变量。稍后我将使用此 int 为使用中断的计时器指定闹钟时间。但是现在，我想我只需要知道如何将该值分配给 int 变量。例如，我在应用程序上键入“42”并点击发送，然后代码获取并将 42 分配给一个 int 变量。我看到代码使用了一个类和一些 void 函数，所以我假设我必须更改它以返回一个值，但到目前为止，我所有的尝试都失败了。任何帮助或见解将不胜感激！顶部到 github 的链接什么都不做 :((

/*
    Based on Neil Kolban example for IDF: https://github.com/nkolban/esp32-snippets/blob/master/cpp_utils/tests/BLE%20Tests/SampleWrite.cpp
    Ported to Arduino ESP32 by Evandro Copercini
*/

#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);

  Serial.println("1- Download and install an BLE scanner app in your phone");
  Serial.println("2- Scan for BLE devices in the app");
  Serial.println("3- Connect to MyESP32");
  Serial.println("4- Go to CUSTOM CHARACTERISTIC in CUSTOM SERVICE and write something");
  Serial.println("5- See the magic =)");

  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);
}

更新：我发现我需要做的是在定义的类中通过引用传递，以便存储“值”的值的地址。以下是我试图通过引用进行此类传递的尝试。然后我需要在设置或循环中调用该变量。所以是的，总而言之：我需要它在“MyCallBacks”类的 Void 函数“onWrite”中接收一个字符串，并将该字符串存储在一个地址中。然后在 main 或循环中访问该字符串。在设置的底部，您可以看到我的一项尝试，但出现错误：

"BLE_write:67:23: 错误: 'stgTimeSpan' 未在此范围内声明 std::string stg1 = &stgTimeSpan;"

希望此更新有所帮助。在下面找到已编辑的代码。

#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();

std::string *passString; 
std::string stgTimeSpan = '\0';
passString = &value;
stgTimeSpan = *passString;


//      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);

  Serial.println("1- Download and install an BLE scanner app in your phone");
  Serial.println("2- Scan for BLE devices in the app");
  Serial.println("3- Connect to MyESP32");
  Serial.println("4- Go to CUSTOM CHARACTERISTIC in CUSTOM SERVICE and write something");
  Serial.println("5- See the magic =)");

  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();

  std::string stg1 = &stgTimeSpan;
}

void loop() {



  // put your main code here, to run repeatedly:
  delay(2000);
}

Answer 1

您可以将值保存在回调之外的全局字符串变量中，并使用 c_str() 从 std::string 中提取字符串。现在您可以在循环中对其执行任何字符串功能。

String yourValue;

类 MyCallbacks：公共 BLECharacteristicCallbacks { 无效 onWrite(BLECharacteristic *pCharacteristic) { std::string value = pCharacteristic->getValue();

    yourValue = value.c_str();
}

}