BLE.begin() -> BLE.end() -> BLE.begin() [again]

[ASabovic]

Hi guys,

I am wondering if it is possible to turn off BLE when I do not need to send some data, and turn it on again when data is ready to be sent? I am trying to enable that part, but every time when BLE.end() function is called seems that I am not able to start the BLE again after some sleep time. In my case, I want to send the simple message from Arduino to my PC, and it works when BLE is constantly ON, but I want to turn it off in order to keep my device in a sleep state, and in that case, decrease the current consumption. Is this implementation possible with the Arduino BLE library?

P.S.
In my case, the BLE service, characteristics, advertising,... are defined in the setup function. Thanks in advance. Cheers! :)

[rmlearney-digicatapult]

#65 covers what you're describing.

Implementing this without a power cycle needs changes to the underlying CordioHCIHook

[ASabovic]

I have already checked this thread and also checked if src/utility/HCICordioTransport.cpp is properly changed in my case and it's same as in #92 but still I am only able to perform 2 cycles and the code breaks.

[ASabovic]

Is there something related to my board as I am using the Arduino Nano 33 BLE Sense based on the ublox chip? I literally changed everything based on this thread but still after only 2 cycles the device breaks and I am not able to continue executing my code. Please help as this is the most important part of my project.

[baconcheese113]

Facing the same issue with Nano 33 IoT, a blank sketch with just BLE.begin() in setup increases power consumption from 22mA to 85mA so being able to turn it off is very important.

I'm trying to turn it on every 10 seconds to do a 1 second scan by calling BLE.begin() and BLE.end() a second later. This seems to work, however when setting back up a service BLE.addService() it crashes

[ASabovic]

In my case, I want to call BLE.begin() when data transfer is needed and after that part is finished call BLE.end() in order to put back my device into sleep state. I am not planning to use BLE very often so this feature is a great opportunity for me to keep BLE "inactive" when I do not need to use it. I tried the solution from these two threads #65 and #92 by changing HCICordioTransport.cpp file with parts that they suggested and confirmed that it works but in my case the code crashes after two cycles and it's not able to back up service and other configuration parts of BLE.

[baconcheese113]

@ASabovic My issue is described here #246
If you just call BLE.begin() and BLE.end() on repeat without adding services, does it work for you indefinitely? Because that works for me, I just can't add event handlers or services after having called BLE.end()

[ASabovic]

I have the same situation, if I just call BLE.begin() and BLE.end() the code runs indefenitely, but if I add anything else after two cycles it will crash. I am able to send the message two times and put the BLE OFF, but after that it just stops and the code crashes. Maybe you can also try this solution proposed in the above mentioned threads and let me know if that method works in your case.

[baconcheese113]

I'm using the latest ArduinoBLE version: 1.3.1 which does include @facchinm 's PR, however the Nano 33 IoT doesn't use HCICordioTransport (ARDUINO_ARCH_MBED is undefined) so no changes to that file would impact my issue.

When trying the BLE.end()/BLE.begin() method, my program crashes trying to add the service. Specifically on this line.

In this loop from GATT.cpp, characteristic->descriptorCount() and descriptor->_refCount return random high numbers right before the crash on the retain() line. Seems like they're trying to read from a corrupted memory address.

for (unsigned int j = 0; j < characteristic->descriptorCount(); j++) {
  BLELocalDescriptor* descriptor = characteristic->descriptor(j);

  descriptor->retain();
  _attributes.add(descriptor);
  descriptor->setHandle(attributeCount());
}

[ASabovic]

Here I am not sure what can cause an issue. Is it possible to change the memory address or to define the specific one where all parameters will be saved? Based on #64 in Nano 33 BLE family the BLE functionality is inside the chip, so there's no need for that extra steps. Furthermore, it doesn't use an UART based transport but Cordio's one. Now, I am bit confused as you said that in your case to change HCICordioTransport will not change anything...I am using the Arduino Nano 33 BLE Sense so maybe in my case I also do not have anything from these changes? Now, I am able to reach 3 cycles but then when my device is connected it crashes and that's the end of the execution. @facchinm @rmlearney-digicatapult any suggestions how to fix this issue?

[rmlearney-digicatapult]

I'm really sorry but I'm just a hobbyist when it comes to Arduino.

One of the Arduino team like @facchinm would be more appropriate.

[ASabovic]

But in #92 you @rmlearney-digicatapult confirmed that the code works for you when you tried to begin and end BLE in cycles. What did you change to make it able to work without breaks? Do you maybe have the code saved somewhere? I think that here you tested the same board that I am using right now (Arduino Nano 33 BLE Sense).

[rmlearney-digicatapult]

Ah. I only did it the once during testing and then realised that cycling the bluetooth connection wasn't a necessary feature of my application so have just left it on ever since. Sorry :(

Try the sketch in #65 on a Nano 33 BLE (not the Sense version) - it might cycle more than once?

[ASabovic]

Aha okay, I understand. Maybe then @facchinm can give as the final answer is this feasible on Nano 33 BLE Sense or not. I chose Sense version as I saw that the ML part is feasible on it. Does Nano 33 BLE (without Sense) support the machine learning part (specifically in my case the person detection model)?