ESP32 Bluetooth Serial and BLE server running together
There is a new kid coming into the arduino-esp32 world. A Bluetooth Serial library that allows you to use Bluetooth (not BLE) like a serial port. This way you can connect the ESP32 over Bluetooth to an Android app like the Serial Bluetooth Terminal and use it as a serial in/out interface.
The library is not yet in the arduino-esp32 repository, but I grabbed a preview from copercini’s repo. It is working fine, I could connect my Android tablet to my ESP32 over Bluetooth and send and receive messages between the two.
Now I wanted to integrate this into my weather station project, where I have already a BLE server running. And it didn’t work. I could get either the BLE server or the Bluetooth serial to work, but not both together.
The mistake I made was that I tried to initialize both in separate function calls. First it was like calling
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void initBLE() { // Initialize BLE BLEDevice::init(apName); BLEDevice::setPower(ESP_PWR_LVL_P7); // Create BLE Server pServer = BLEDevice::createServer(); // ... // initialize BLE callbacks and characteristics // ... // Start the service pService->start(); // Start advertising pAdvertising = pServer->getAdvertising(); pAdvertising->start(); } |
and then calling
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bool initBtSerial() { if (!SerialBT.begin(apName)) { return false; } return true; } |
depending on the sequence I called the two functions the system either crashed or only one of the two services were working.
After a lot of trial and error and discussions with copercini I figured out the solution. The initialization of BLE and Bluetooth Serial must somehow be at the same time. The working solution:
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void initBlueTooth() { // Initialize BLE BLEDevice::init(apName); BLEDevice::setPower(ESP_PWR_LVL_P7); SerialBT.begin(apName); // Create BLE Server pServer = BLEDevice::createServer(); // ... // initialize BLE callbacks and characteristics // ... // Start the service pService->start(); // Start advertising pAdvertising = pServer->getAdvertising(); pAdvertising->start(); } |
The working sequence seems to be
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Init BLE device => BLEDevice::init(apName); Init Bluetooth Serial => SerialBT.begin(apName); Then do the rest of the BLE initialisation like - create server - add callbacks to server - add characteristics - start server - start advertising |
The full code of the initialization routine can be found in my Github repo.
