Generic Default Transition Time Server

The DTT Server provides a common way to specify the state transition time for other models on any element. If a DTT Server is not present on the model’s element, use the DTT Server model instance that is present on the element with the largest address that is smaller than the address of the given element. This way, if other generic models on any element receive state change commands without transition parameters, they will use the default transition time specified by the DTT Server model. The DTT Server can then define a consistent transition time for all states on their elements, without depending on client configurations.

Configuration

The following configuration parameters are associated with the Generic DTT Server model:

States

The Generic Level Server model contains the following state:

Generic Default Transition Time: int32_t

This state can have the following values:

  • 0 to perform the state change instantly or when no transition is planned

  • Positive number of milliseconds that defines the transition time

  • SYS_FOREVER_MS if the transition time is undefined

On the air, the transition time is encoded into a single byte, and loses some of its granularity:

  • Step count: 6 bits (range 0x00 to 0x3e)

  • Step resolution: 2 bits

    • Step 0: 100-millisecond resolution

    • Step 1: 1-second resolution

    • Step 2: 10-second resolution

    • Step 3: 10-minute resolution

The state is encoded with the highest resolution available, and rounded to the nearest representation. Values lower than 100 milliseconds and higher than 0 are encoded as 100 milliseconds. Values higher than the max value of 620 minutes are encoded as “undefined”.

The DTT Server holds the memory for this state itself, and optionally notifies the user of any changes through bt_mesh_dtt_srv.update_handler. If your application changes the transition time manually, the change must be published using bt_mesh_dtt_srv_pub().

Extended models

None.

Persistent storage

The Generic Default Transition Time is stored persistently if CONFIG_BT_MESH_DTT_SRV_PERSISTENT is enabled.

API documentation

Header file: include/bluetooth/mesh/gen_dtt_srv.h
Source file: subsys/bluetooth/mesh/gen_dtt_srv.c
Generic Default Transition Time Server