InsufficientSpace error when sending notification with byte array in characteristic

[aidengk-iris]

Dear all,

I am trying to stream a few hundred bytes regularly from a characteristic. I was able to create an byte array and set it as the value of a characteristic thanks to #334 :

However, when I send notification with 320 Bytes, I received InsufficientSpace error from the notify() function.
When I notify with 240 Bytes or 120 Bytes, I could receive them correctly.

I suppose there's a maximum length for the notification data. If so, is it still possible to use GATT to regularly stream hundreds of Bytes?

The data chunk I plan to stream is around 640 Bytes. If notification doesn't fit the application, would you suggest some other methods?

Thank you!

[lulf]

Try to adjust your l2cap MTU to fit the notification size. (Set as a generic on HostResources, potentially also on your controller settings depending on which controller).

For this kind of application, I would recommend looking into l2cap connection oriented channels though, as it is more appropriate for streaming.

[aidengk-iris]

Thank you @Lul , increasing L2CAP MTU to 400 indeed removed the InsufficientSpace error. But for some reason I could not receive the notifications on the PC side. Guess I should try to stream on L2CAP following the examples.

Am I correct to think that GATT is suitable for low-paced relatively small sized data and L2CAP is better for streaming large amount of data?

[lulf]

Thank you @Lul , increasing L2CAP MTU to 400 indeed removed the InsufficientSpace error. But for some reason I could not receive the notifications on the PC side. Guess I should try to stream on L2CAP following the examples.

Could be there some other bottlenecks, might be worth checking with wireshark.

Am I correct to think that GATT is suitable for low-paced relatively small sized data and L2CAP is better for streaming large amount of data?

It's not a huge difference performance wise, some less hops/no intermediary storage on the device. But the API for l2cap is more UDP-like with send() recv() data on a channel.

[aidengk-iris]

Thank you very much!