Receive Two Characteristics with BLE

cards2019
Posts: 6
Joined: Sat Mar 06, 2021 8:14 am

Receive Two Characteristics with BLE

Postby cards2019 » Sun Mar 21, 2021 7:19 am

Hello, I have am trying to receive two characteristics on an ESP32. I have an Arduino that is sending a random integer between 1 and 100 and the ESP32 is reading it. I am using the BLE_client example and everything works fine when reading one characteristic. I've been trying to edit the example to do the same thing for a second characteristic, but I feel like I'm getting way off. I've attached my code that sends data. I've also attached the modified BLE client example, but its pretty messy because I don't understand this well. With this modified client example, it won't even connect to the arduino. Does anyone happen to have any tips for how to structure code to receive a second characteristics or have example of an ESP32 reading two characteristics? Thank you.

Code: Select all

//this arduino sends two numbers
#include <ArduinoBLE.h>
#include <Arduino_LSM6DS3.h>

BLEService IMUservice("1101");
BLEUnsignedCharCharacteristic pitchChar("2101", BLERead | BLENotify);
BLEUnsignedCharCharacteristic rollChar("3101", BLERead | BLENotify);

void setup() {
Serial.begin(9600);
pinMode(LED_BUILTIN, OUTPUT);
  
if (!BLE.begin()) 
{
while (1);
}

BLE.setLocalName("IMU");
BLE.setAdvertisedService(IMUservice);
IMUservice.addCharacteristic(pitchChar);
IMUservice.addCharacteristic(rollChar);
BLE.addService(IMUservice);

BLE.advertise();
}

void loop() 
{
BLEDevice central = BLE.central();

if (central) 
{
digitalWrite(LED_BUILTIN, HIGH);

while (central.connected()) {
//      //pitch+=1;
//      //roll-=1;
      int Pitch=random(99);
      int Roll=random(99);
      pitchChar.writeValue(Pitch);
      Serial.print(Pitch);
      rollChar.writeValue(Roll);
      Serial.print(Roll);
      delay(100);
 }
}
digitalWrite(LED_BUILTIN, LOW);
}

Code: Select all

/**
 * A BLE client example that is rich in capabilities.
 * There is a lot new capabilities implemented.
 * author unknown
 * updated by chegewara
 */

#include <M5Core2.h>
#include "BLEDevice.h"
//#include "BLEScan.h"

// The remote service we wish to connect to.
static BLEUUID serviceUUID("1101");
// The characteristic of the remote service we are interested in.
static BLEUUID    charUUID("2101");
static BLEUUID    charUUID1("3101");

static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLERemoteCharacteristic* pRemoteCharacteristic1;
static BLEAdvertisedDevice* myDevice;
int carmpitch;
char cp[10];

static void notifyCallback(
  BLERemoteCharacteristic* pBLERemoteCharacteristic,
  uint8_t* pData,
  size_t length,
  bool isNotify) {
//    Serial.print("Notify callback for characteristic ");
//    Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
//    Serial.print(" of data length ");
//    Serial.println(length);
//    Serial.print("data: ");
    Serial.printf("%d\n", pData[0]);
    //int pitch = pData[0] - '0';
    carmpitch = (int)pData[0];
    if(carmpitch >= 10){
      sprintf(cp,"%02d", carmpitch); //  XXX.XX
    } else {
       sprintf(cp, "%2d \n", carmpitch);
    }
    M5.Lcd.setCursor(100, 100);
    M5.Lcd.print(cp); //cp or carmpitch
    //Serial.println(carmpitch);
}

static void notifyCallback1(
  BLERemoteCharacteristic* pBLERemoteCharacteristic1,
  uint8_t* pData1,
  size_t length,
  bool isNotify) {
//    Serial.print("Notify callback for characteristic ");
//    Serial.print(pBLERemoteCharacteristic->getUUID().toString().c_str());
//    Serial.print(" of data length ");
//    Serial.println(length);
//    Serial.print("data: ");
    Serial.printf("%d\n", pData1[0]);
    Serial.print("\n");
  }

class MyClientCallback : public BLEClientCallbacks {
  void onConnect(BLEClient* pclient) {
  }

  void onDisconnect(BLEClient* pclient) {
    connected = false;
    Serial.println("onDisconnect");
  }
};

bool connectToServer() {
    Serial.print("Forming a connection to ");
    Serial.println(myDevice->getAddress().toString().c_str());
    
    BLEClient*  pClient  = BLEDevice::createClient();
    Serial.println(" - Created client");

    pClient->setClientCallbacks(new MyClientCallback());

    // Connect to the remove BLE Server.
    pClient->connect(myDevice);  // if you pass BLEAdvertisedDevice instead of address, it will be recognized type of peer device address (public or private)
    Serial.println(" - Connected to server");

    // Obtain a reference to the service we are after in the remote BLE server.
    BLERemoteService* pRemoteService = pClient->getService(serviceUUID);
    if (pRemoteService == nullptr) {
      Serial.print("Failed to find our service UUID: ");
      Serial.println(serviceUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }
    Serial.println(" - Found our service");


    // Obtain a reference to the characteristic in the service of the remote BLE server.
    pRemoteCharacteristic = pRemoteService->getCharacteristic(charUUID);
    if (pRemoteCharacteristic == nullptr) {
      Serial.print("Failed to find our characteristic UUID: ");
      Serial.println(charUUID.toString().c_str());
      pClient->disconnect();
      return false;
    }

    // Obtain a reference to the characteristic in the service of the remote BLE server.
    pRemoteCharacteristic1 = pRemoteService->getCharacteristic(charUUID1);
    if (pRemoteCharacteristic1 == nullptr) {
      Serial.print("Failed to find our characteristic UUID: ");
      Serial.println(charUUID1.toString().c_str());
      pClient->disconnect();
      return false;
    }    
    
    Serial.println(" - Found our characteristics");

    // Read the value of the characteristic.
    if(pRemoteCharacteristic->canRead()) {
      std::string value = pRemoteCharacteristic->readValue();
      Serial.print("The characteristic value was: ");
      Serial.println(value.c_str());
    }

        // Read the value of the characteristic.
    if(pRemoteCharacteristic1->canRead()) {
      std::string value1 = pRemoteCharacteristic1->readValue();
      Serial.print("The characteristic value was: ");
      Serial.println(value1.c_str());
    }

    if(pRemoteCharacteristic->canNotify())
      pRemoteCharacteristic->registerForNotify(notifyCallback);
          if(pRemoteCharacteristic1->canNotify())
      pRemoteCharacteristic1->registerForNotify(notifyCallback1);

    connected = true;
    return true;
}
/**
 * Scan for BLE servers and find the first one that advertises the service we are looking for.
 */
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
 /**
   * Called for each advertising BLE server.
   */
  void onResult(BLEAdvertisedDevice advertisedDevice) {
    Serial.print("BLE Advertised Device found: ");
    Serial.println(advertisedDevice.toString().c_str());

    // We have found a device, let us now see if it contains the service we are looking for.
    if (advertisedDevice.haveServiceUUID() && advertisedDevice.isAdvertisingService(serviceUUID)) {

      BLEDevice::getScan()->stop();
      myDevice = new BLEAdvertisedDevice(advertisedDevice);
      doConnect = true;
      doScan = true;

    } // Found our server
  } // onResult
}; // MyAdvertisedDeviceCallbacks
 

void setup() {
  M5.begin();
  M5.Lcd.fillScreen(BLACK);
  M5.Lcd.setTextColor(GREEN , BLACK);
  M5.Lcd.setTextSize(2);
  delay(2000);
  Serial.begin(115200);
  Serial.println("Starting Arduino BLE Client application...");
  BLEDevice::init("");

  // Retrieve a Scanner and set the callback we want to use to be informed when we
  // have detected a new device.  Specify that we want active scanning and start the
  // scan to run for 5 seconds.
  BLEScan* pBLEScan = BLEDevice::getScan();
  pBLEScan->setAdvertisedDeviceCallbacks(new MyAdvertisedDeviceCallbacks());
  pBLEScan->setInterval(1349);
  pBLEScan->setWindow(449);
  pBLEScan->setActiveScan(true);
  pBLEScan->start(5, false);
} // End of setup.


// This is the Arduino main loop function.
void loop() {

  // If the flag "doConnect" is true then we have scanned for and found the desired
  // BLE Server with which we wish to connect.  Now we connect to it.  Once we are 
  // connected we set the connected flag to be true.
  if (doConnect == true) {
    if (connectToServer()) {
      Serial.println("We are now connected to the BLE Server.");
    } else {
      Serial.println("We have failed to connect to the server; there is nothin more we will do.");
    }
    doConnect = false;
  }

  if(connected==false && doScan==true){
    BLEDevice::getScan()->start(0);  // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
  }

  // If we are connected to a peer BLE Server, update the characteristic each time we are reached
  // with the current time since boot.
//  if (connected) {
//    String newValue = "Time since boot: " + String(millis()/1000);
//    Serial.println("Setting new characteristic value to \"" + newValue + "\"");
//    
//    // Set the characteristic's value to be the array of bytes that is actually a string.
//    pRemoteCharacteristic->writeValue(newValue.c_str(), newValue.length());
//  }else if(doScan){
//    BLEDevice::getScan()->start(0);  // this is just eample to start scan after disconnect, most likely there is better way to do it in arduino
//  }

  delay(1000); // Delay a second between loops.
} // End of loop

User avatar
0miker0
Posts: 10
Joined: Fri Dec 01, 2017 1:14 pm

Re: Receive Two Characteristics with BLE

Postby 0miker0 » Mon Mar 22, 2021 12:16 pm

Not sure if this will be of help or not but I have my esp32 reading temperature and humidity from an Aliexpress beacon: https://twitter.com/mikerankin/status/1 ... 2578297856

cards2019
Posts: 6
Joined: Sat Mar 06, 2021 8:14 am

Re: Receive Two Characteristics with BLE

Postby cards2019 » Sun Mar 28, 2021 1:59 am

Thank you for the reply. I was able to figure out another way to read multiple characteristics, but there's plenty of good stuff in that code that I might use as a guide for other things.

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