BLE using ESP 32

Question

I am trying to program a BLE client using an ESP32. I have used the attached code (which is the example code from the example section). My problem right now is, how do I get it to show the MAC address of the scanned device only, and how do I change this MAC address into a JSON format for a LoRa chip to transmit? Thank you so much for your time to read this post.

/*
   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);
}

Answer 1

The result of your scan is foundDevices, which contains a list of all found devices. We can iterate through it to access the devices. The List contains BLEAdvertisedDevices which have a method called getAddress(). The address can be converted to a string using toString(). You can print the string or put it into your json container.

Your loop-code could look like this:

void loop() {
  // put your main code here, to run repeatedly:
  BLEScanResults foundDevices = pBLEScan->start(scanTime, false);
  Serial.print("Devices found: ");
  for (int i = 0; i < foundDevices.getCount(); ++i)
  {
    std::string address = foundDevices.getDevice(i).getAddress().toString();
    int rssi = foundDevices.getDevice(i).getRSSI();
    Serial.print(address.c_str());
    Serial.print(rssi);
    // TODO: Insert into JSON
  }
  Serial.println(foundDevices.getCount());
  Serial.println("Scan done!");
  pBLEScan->clearResults();   // delete results fromBLEScan buffer to release memory
  delay(2000);
}