nRF5 SDK for Mesh
Provisioning over GATT1 and the Proxy protocol2 are optional features that allow a device without support for the advertising bearer to provision and/or communicate with the mesh network through a device using a GATT interface.
A device does not need to support both the GATT provisioning bearer (PB-GATT) and the Proxy feature, but in the Light Switch example applications, both are supported by default. The sequence diagram below shows how a device is provisioned over GATT and then transitions to being a GATT Proxy server.
The figure shows that the device first advertises both connectable and non-connectable Unprovisioned Device beacons. The connectable beacon is used for PB-GATT and the non-connectable is for PB-ADV. The connectable beacon has a slightly different format as it also includes the Mesh Provisioning Service UUID3. PB-GATT uses the interface provided in
mesh_adv.h for advertising. Immediately after the provisioner has connected to the device, it stops advertising both beacons. When the provisioning process is complete, the device must reset its GATT database to comply with the following requirement from the Mesh Profile Specification v1.0:
A device may support the Mesh Provisioning Service or the Mesh Proxy Service or both. If both are supported, only one of these services shall be exposed in the GATT database at a time.3
The reset is done by the helper module
mesh_provisionee.c. To reset the database, the SoftDevice is disabled and re-enabled. This means that any application service or setting needs to be re-initialized after provisioning. This is done in the
prov_complete_cb() callback from
mesh_provisionee.h. For example, in the Light Switch server example:
GATT support in mesh is provided through the following source files:
core_tx.hinterface for the GATT bearer.
Furthermore, there are two defines, MESH_FEATURE_PB_GATT_ENABLED and MESH_FEATURE_GATT_PROXY_ENABLED, that control the inclusion of GATT related code in other sources. For example, the Configuration server (
models/foundation/src/config_server.c) behaves diffently when MESH_FEATURE_GATT_PROXY_ENABLED is supported. MESH_FEATURE_PB_GATT_ENABLED controls inclusion of all GATT related code in
examples/common/src/mesh_provisionee.c, whereas MESH_FEATURE_GATT_PROXY_ENABLED controls the GATT Proxy feature specifically.
1 Mesh Profile Specification v1.0 Section 5.2.2, page 229.
2 Mesh Profile Specification v1.0 Chapter 6, page 260.
3 Mesh Profile Specification v1.0 Section 220.127.116.11.1, page 271.
4 Mesh Profile Specification v1.0 Chapter 7, page 269.