Hi all,
I'm currently working through the BLE_client example in the ESP32 BLE Arduino library. My goal is to read heart rate data from my Polar Grit X (whose serviceUUID and charUUID are detailed in the code below). My charUUID is becoming nullptr somehow through the program.
/**
* A BLE client example that is rich in capabilities.
* There is a lot new capabilities implemented.
* author unknown
* updated by chegewara
*/
#include "BLEDevice.h"
//#include "BLEScan.h"
// The remote service we wish to connect to.
static BLEUUID serviceUUID("0000feee-0000-1000-8000-00805f9b34fb"); // smart band: 0000fee0-0000-1000-8000-00805f9b34fb fitbit: adabfb00-6e7d-4601-bda2-bffaa68956ba
// The characteristic of the remote service we are interested in.
static BLEUUID charUUID("00002a37–0000–1000–8000–00805f9b34fb"); // custom char uuid: fb005c51-02e7-f387-1cad-8acd2d8df0c8
static boolean doConnect = false;
static boolean connected = false;
static boolean doScan = false;
static boolean notification = false;
static BLERemoteCharacteristic* pRemoteCharacteristic;
static BLEAdvertisedDevice* myDevice;
class MyClientCallback : public BLEClientCallbacks {
void onConnect(BLEClient* pclient) {
}
void onDisconnect(BLEClient* pclient) {
connected = false;
Serial.println("onDisconnect");
}
};
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.println((char*)pData);
if (bitRead(pData[0], 0) == 1) {
Serial.println(F("16bit HeartRate Detected"));
} else {
Serial.println(F("8bit HeartRate Detected"));
}
if (length == 2) {
Serial.print("Heart Rate ");
Serial.print(pData[1], DEC);
Serial.println("bpm");
}
}
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");
pClient->setMTU(517); //set client to request maximum MTU from server (default is 23 otherwise)
// 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;
}
Serial.println(" - Found our characteristic");
// 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());
}
if(pRemoteCharacteristic->canNotify())
pRemoteCharacteristic->registerForNotify(notifyCallback);
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() {
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 we are connected to a peer BLE Server, update the characteristic each time we are reached
// with the current time since boot.
if (connected) { // edited for heart rate capture
if (notification == false) {
Serial.println("Turning Notification On");
const uint8_t onPacket[] = {0x1, 0x0};
pRemoteCharacteristic->getDescriptor(BLEUUID((uint16_t)0x2902))->writeValue((uint8_t*)onPacket, 2, true);
}
}
delay(1000); // Delay a second between loops.
} // End of loop
Here is Serial Monitor:
15:47:28.548 -> Starting Arduino BLE Client application...
15:47:33.412 -> BLE Advertised Device found: Name: Polar Grit X A51C652F, Address: a0:9e:1a:a5:1c:65, manufacturer data: 6b0072080da1800300000000, serviceUUID: 0000feee-0000-1000-8000-00805f9b34fb
15:47:33.412 -> Forming a connection to a0:9e:1a:a5:1c:65
15:47:33.412 -> - Created client
15:47:38.471 -> - Connected to server
15:47:39.474 -> - Found our service
15:47:39.474 -> Failed to find our characteristic UUID: <NULL>
15:47:39.512 -> We have failed to connect to the server; there is nothin more we will do.
15:47:39.512 -> onDisconnect
How can I resolve this error? Thank you all for the hard work!