Recently customer met a problem ,when he test the FSC-BW226 bluetooth+wifi module .
We just implemented our application using AT+BTSEND and figured out some problems when send a large number of data.
He asked why i can only send 20 bytes instead of 21 bytes .
You may konw that bluetooth transmission do not have limited about bytes .and 21 bytes it is also very very small data volume.
Usually this may not possible to happen .
So why this happens ,we just asked customer send some screen shot to us .Then We found that customer use this APP ''nRF Connect'' . ''nRF Connect'' it is a most common android APP that you can download from google store.
You may did not noticed that this APP ''nRF Connect '',default setting is 20 bytes ,you need set MTU parameter first ,we just set to 100 bytes ,it works .Refer below image.
iPhone you can use ''LightBlue'' ,it works and this app no need set MTU parameter .
Any similar question ,you can feel free to contact feasycom team .