SWRU271I October 2010 – January 2020 CC2540 , CC2540T , CC2541 , CC2541-Q1 , CC2640R2F
The L2CAP layer sits on top of the HCI layer and transfers data between the upper layers of the host (GAP, GATT, application, and so forth) and the lower-layer protocol stack. This layer multiplexes higher-level protocol and reassembles data exchanged between the host and the protocol stack. L2CAP permits higher-level protocols and applications to transmit and receive upper-layer data packets (L2CAP Service Data Units, [SDUs]) up to 64KB long. The amount of memory available on the specific device implementation limits the size. The CC254x and the 1.4.1 stack support an effective MTU size of 23, set by L2CAP_MTU_SIZE in l2cap.h. Changing the L2CAP_MTU_SIZE results in incorrect stack behavior.