The HostController Interface (HCI) is an interface via which status and control information is transferred between the host controller and a USB interface or an interface to Bluetooth and the corresponding protocol stack.
The Host Controller Interface (HCI) is based on the Logical Link Control and Adaptation Protocol( L2CAP). It manages the connection parameters between the communication partners and displays the device settings. In Bluetooth, the HCI interface represents the interface between the air interface and the Bluetooth protocol stack. In Bluetooth, the interface is located between the Bluetooth host protocols, which are located above the Link Manager Protocol( LMP), the Link Manager and the functions of the baseband and RF controllers, and the RF module.
The designation of the HCI interface is based on the interface technology. If the HCI interface is in Bluetooth between the Bluetooth protocol stack and the application, it is the Bluetooth Embedded Control Interface( BECI). If it is about the host adapter in SATA, then it is the Advanced Host Controller Interface( AHCI); with a host adapter for USB 2.0 the HCI interface is called Enhanced Host Controller Interface( EHCI) and for USB 1.1 Open Host Controller Interface( OHCI).