Service not discovered in BLE_Client example

[SensorsIot]

I use the BLE_notify example without changes and try to connect to it using the BLE_Client example. The only changes I did there was to copy the two UUID strings of the notify example to the client example to be sure they match.
NRF connect shows the service but BLE_Client does not show it and also does not connect.
Output: BLE Advertised Device found: Name: MyESP32, Address: 24:0a:c4:12:ef:a2, txPower: -21
I had this issue with many other examples but I am pretty sure it worked last week.
To be sure I also downloaded the newest ESP32 environment from GitHub, with no change
I also have a Xiaomi Flower care device around:
Output: BLE Advertised Device found: Name: Flower care, Address: c4:7c:8d:62:87:f7, serviceUUID: 0000fe95-0000-1000-8000-00805f9b34fb
If I copy this UUID to the client sketch, it connects.

[chegewara]

Hi,
one question, are you using library from https://github.com/nkolban/ESP32_BLE_Arduino or from https://github.com/nkolban/esp32-snippets. In other words, in arduino ide are installing library from zip file or from library manager?

[SensorsIot]

From the original distribution (with git clone)

[chegewara]

Original distribution is https://github.com/nkolban/esp32-snippets

[SensorsIot]

So there are differences between espressif/arduino-esp32 and https://github.com/nkolban/esp32-snippets? Which one do you suggest?

[chegewara]

At the moment, until we dont get support c++ exceptions in arduino-esp32 i suggest to not change to esp32-snippets, and when we have c++ exceptions working in arduino-ide most likely library delivered with arduino-esp32, which you call original distribution, will be updated.

Back to your issue, i will investigate it and back to you soon. In mean time, can you turn on verbose logging in arduino-ide and provide more logs?

[SensorsIot]

I switched it on and compiled the client file. Where should I post the log?

[chegewara]

pastebin or here

[SensorsIot]

It is here:
https://pastebin.com/5299TxCV

[chegewara]

Ok, ive found the problem. Those two examples are not prepared to work with each other without some changes. As you can see in this line https://github.com/nkolban/ESP32_BLE_Arduino/blob/f8fe9d7cdfb20caa54b70849826d1ac6e375ff78/examples/BLE_client/BLE_client.ino#L78
BLE_client expecting that server is advertising UUID, but BLE_notify example is not advertising any UUID. You can change it very easy by adding this line
pServer->getAdvertising()->addServiceUUID(BLEUUID(SERVICE_UUID)); somwhere in here https://github.com/nkolban/ESP32_BLE_Arduino/blob/f8fe9d7cdfb20caa54b70849826d1ac6e375ff78/examples/BLE_notify/BLE_notify.ino#L78
tis will let you to connect 2 esp32 by using BLE_client and BLE_notify examples. There is one more thing you have to remember. When you are advertising 128 bit UUID then name of device cant be longer than 5 characters.

[chegewara]

You can also change this line https://github.com/nkolban/ESP32_BLE_Arduino/blob/f8fe9d7cdfb20caa54b70849826d1ac6e375ff78/examples/BLE_client/BLE_client.ino#L78 and search device you want to connect to not by advertised UUID but ie by name, or served service etc

[SensorsIot]

Now it works. Very good! Thank you very much for your help. Now I can go on with my Polar H7 emulation... And with my new video where I need BLE UART functionality. So it is well possible that I have to come back because for the moment I can only transfer a few characters to my Smartphone...
Just a small question concerning your additional line: Why do I have to use BLEUUID(SERVICE_UUID) and not only (SERVICE_UUID)?

[chegewara]

You can use both, BLEUUID(SERVICE_UUID) and (SERVICE_UUID) because this method is overloaded and can be used with BLEUUID or with string uuid.

EDIT you can use both only in case if SERVICE_UUID is 128 bit uuid in string variable. In case you want to use 16 or 32 bit uuid only BLEUUID(SERVICE_UUID) works

[SensorsIot]

I try now to read the values sent by notify.
in BLE_notify I inserted:
cscCharacteristic.setValue(csc, 11);
cscCharacteristic.notify();

In BLE_client I am able to see the values once during connect of the characteristics:
in connectToServer(BLEAddress pAddress) at the bottom I inserted:
// Read the value of the characteristic.
std::string value = pRemoteCharacteristic->readValue();
Serial.println("The characteristic value was: ");
for (int i = 0; i < value.length(); i++) Serial.println(value[i], HEX);
Serial.print("length: ");
Serial.println(value.length());

But not during notifyCallback:

static void notifyCallback(
BLERemoteCharacteristic* pBLERemoteCharacteristic,
uint8_t* pData,
size_t length,
bool isNotify) {
Serial.print("Notify callback for characteristic ");
Serial.println(pBLERemoteCharacteristic->getUUID().toString().c_str());

Serial.println("The characteristic value was: ");
// Read the value of the characteristic.
std::string value = pBLERemoteCharacteristic->readValue();
for (int i = 0; i < value.length(); i++) Serial.println(value[i], HEX);
Serial.print("length: ");
Serial.println(value.length());
}
The callback is called, but the line std::string value = pBLERemoteCharacteristic->readValue(); blocks the execution
In NRFconnect the csc value counts up

The whole code is here (strongly based on the notify example)
https://pastebin.com/PbtSvvVU

And the notifier: https://pastebin.com/0ngKNkef (based on the Cadence and speed service)

[chegewara]

In my case with original BLE_notify and BLE_client i can receive notifications, but i will investigate custom code.

[chegewara]

I see the problem. Here you have created chracteristic with notify:
BLECharacteristic cscCharacteristic(BLEUUID((uint16_t)0x2A5B), BLECharacteristic::PROPERTY_READ | BLECharacteristic::PROPERTY_NOTIFY); thats good, but if you will check with nRF connect there is missing something. With properly implemented notify/indicate functionality you will see three arrows like on this picture http://a2.mzstatic.com/us/r30/Purple18/v4/21/65/4d/21654db0-6c4e-2237-18a5-624b22e783da/screen696x696.jpeg

This leads us to conclusion there is missing something. Every characteristic with notify and/or indicate needs to have descriptor 2902. There is special library which help to create and add this descriptor BLE2902.