RE: Increasing the MTU Android fails to write characteristic

Simonr — Wed, 08 Jan 2020 09:39:19 GMT

I believe that the Android device won't accept higher MTU values than 255 in this case, which is why you see this error I believe. It is indeed not recommended to set the MTU size higher than 255, seeing as that's how big the DLE (Data Length Extention) feature allows the payload of each packet to be. You can see more on how to achieve maximum throughput in this blog post (keep in mind that this is for Bluetooth 5, so some features won't be available in a BLE 4.2 connection).

So, while 255 is not a hard limit, it's just the highest supported MTU size at the time being, and trying to send more data in each packet will lead to errors and eventual packet loss between devices I believe.

Best regards,

Simon