BLE Characteristics Read/Write Data Getting Truncated

[bwinklesky]

I'm using the Read and Write characteristics and serializing JSON data that has a length of 1215. When reading the response from a mobile app, the data is getting truncated to a length of 765. Using C++ the same data doesn't get truncated and I can read and write without being truncated.

Is there a setting in I need to adjust when setting up the characteristic in NF?

[alberk8]

If ESP32 acting as a Periperal (Server) or Central (client). For peripheral mode the max mtu that can be set by the calling program is 517 bytes. But on nF for Central there is no setting available (default is 23 bytes).

[bwinklesky]

Ok thanks. ESP32 is acting as a peripheral. I'll need to rethink my DTO strategy.

[alberk8]

More info.
🔹 Practical Notes

iOS: maximum MTU it will request is 185, giving 182 usable bytes.

Android: can go higher (commonly 247 MTU → 244 usable bytes), some stacks support the full 517.

ESP32: supports up to 517, but the final MTU is the minimum of (your local request, peer’s request, 517).

[bwinklesky]

Thanks for the notes. I'm using .NET MAUI for the mobile apps and it will be interesting to see how the different platforms behave. Hopefully, the crossplatform library i'm using will handle the differences gracefully.