Question

请帮帮我，我尝试过 BLE 扫描，但是当我调用 MyAdvertisedDeviceCallbacks 类时，设备找到的结果为 0，但是当我不调用该类时，找到的设备显示结果为 3。我的代码有问题吗？我使用的是 ESP32 Dev Kit V1

这是我的代码：

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

#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);
}

这是结果：

Advertised Device: Name: honor Band 3-f15, Address: 34:12:f9:03:1f:15, appearance: 0, manufacturer data: 7d02010300ffcc, serviceUUID: 00001812-0000-1000-8000-00805f9b34fb, txPower: 4 
Advertised Device: Name: honor Band 3-f15, Address: 34:12:f9:03:1f:15, appearance: 0, manufacturer data: 7d02010300ffcc, serviceUUID: 00001812-0000-1000-8000-00805f9b34fb, txPower: 4 
Advertised Device: Name: Charge HR, Address: f5:02:71:f9:46:a7, serviceUUID: adabfb00-6e7d-4601-bda2-bffaa68956ba, txPower: -6 
Advertised Device: Name: honor Band 3-f15, Address: 34:12:f9:03:1f:15, appearance: 0, manufacturer data: 7d02010300ffcc, serviceUUID: 00001812-0000-1000-8000-00805f9b34fb, txPower: 4 
Advertised Device: Name: honor Band 3-f15, Address: 34:12:f9:03:1f:15, appearance: 0, manufacturer data: 7d02010300ffcc, serviceUUID: 00001812-0000-1000-8000-00805f9b34fb, txPower: 4 
Devices found: 0
Scan done!

Answer 1

您没有说明您使用的是哪个版本的 ESP32 Arduino 代码，但是 ESP32 Arduino BLE 1.0.5 版和新发布的 1.0.6 版中的 BLE 扫描码有问题。在较早的 1.0.4 版本中，扫描结果每次扫描仅报告每个设备一次，并正确报告找到的唯一设备的数量。在这些更高版本中，相同的设备在扫描过程中被多次错误报告，并且总数为零。这似乎是最新版本的 BLE 扫描代码中的错误，而不是您的示例草图。

根据您得到的结果，它应该只显示两个唯一的广告设备，并且设备数量：2

Answer 2

作为后续，在查看最近对 ESP32 Arduino github 站点上的库文件 BLEScan.cpp 的更改时，似乎 BLE 扫描操作更改的来源来自 2 个更改2020 年晚些时候（10 月/11 月）。

多次显示找到的 BLE 设备：这是由于 BLEScan 构造函数发生了变化，将 scan_duplicate 参数更改为使用的扫描参数。这并没有考虑到调用 BLEScan.setAdvertisedDeviceCallbacks() 时，wantDuplicates 参数显然被忽略的事实。
设备计数始终为 0：这是由于跟踪扫描结果的操作发生了变化。该操作的一个明显变化是，当 BLE 扫描操作具有用户扫描回调时，扫描设备的跟踪被禁用（这就是计数始终为 0 的原因）！尽管这在源代码中很明显（注释说明了这一点），但对于库用户来说并不明显，因为使用 BLE 扫描的示例没有提到这一点。

总而言之，您所看到的似乎就是编写代码的目的。就我个人而言，我不同意这些操作上的更改，并且在我的使用中，我修改了 BLEScan 库，使其像在这 2 次更改之前一样操作。

发现 BLE 扫描仪设备 0

2 个答案: