RE: is the GATT client same as master

RK — Sat, 06 Jun 2015 12:52:24 GMT

No this is a distinction which some books are better than others at explaining.

Master and Slave are GAP roles defined down at the link layer. One device advertises, the other connects to it, they are both then in the connected state however the one which was originally advertising is the slave and the one which connected is the master. This just determines who starts communication at each interval (the master) and who is in 'control' of the connection, the master.

GATT is several layers in the protocol higher and defines GATT Server and GATT Client. A Server has data and a Client reads/write/uses that data. However either the Master and/or the Slave can take either GATT side, or both of them. The GATT Server and Client just uses the underlying fact they are connected, who's master and who's slave in the connection doesn't matter. As every BTLE device has to have a minimum GAP Profile implementation on it, whether it's a Master or a Slave, either can take either role.