I am trying to make an app, that when it sees a specific bluetooth device to connect to it and send a command and before loose that connection to send another command. The device is standard bluetooth serial device. Is there a way to check when i am going to loose the connection?
1 Answers
No unfortunately Bluetooth doesn't work this way. You are usually notified that the remote device disconnected and you can even get the disconnection reason (e.g. BT_HCI_REMOTE_USER_TERMINATED_CONNECTION), but by then it is already too late and the link between your device and the remote device is already lost. Generally speaking, the way a disconnection works is that there are empty Bluetooth packets sent back and forth between the two devices (similar to an ACK) to indicate that the link is alive. If that packet does not arrive after a certain timeout, the BLE stack throws an event to the application notifying it that the connection has been lost (i.e. a disconnection event).
If you are using Bluetooth Low Energy, and if you are in control of both devices (your one and the remote one), then you could implement additional communication on the advertising channels. This is not as efficient as performing the communication through a connection, but you can advertise this additional command upon disconnection, and the remote device would scan for this new command upon disconnection as well.
I hope this helps.
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