RE: What is the process of sending long (chunked) messages over NUS?

luopio — Tue, 14 Dec 2021 08:25:25 GMT

Thanks Edvin! This is good advice. I think I got sidetracked by seeing things like: https://github.com/NordicSemiconductor/Android-BLE-Library/blob/master/ble/src/main/java/no/nordicsemi/android/ble/data/DataSplitter.java#L28-L29 in the code and assumed there is some internal logic in splitting a long NUS message to several pieces.

I've added requestMtu() calls to our library now and let's see if that resolves the issue.

RE: What is the process of sending long (chunked) messages over NUS?

Edvin — Fri, 10 Dec 2021 14:55:09 GMT

Hello,

Perhaps you need to look in the other end, and check how Flutter handles long messages in BLE. 20 bytes is not a hard limit. Typically devices will negotiate a higher message length (MTU) after connection. Perhaps this doesn't happen when you are using flutter?

You can always try to capture a sniffer trace using the nRF Sniffer for Bluetooth Low Energy and compare the data on air when you are using the Nordic app.

But my guess is that you need to look into the Flutter library, and see how it handles a larger MTU/MTU updates.

Best regards,

Edvin