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Integrating the framework with existing Softdevice Applications

This file will go through the needed changes by using the BLE_app_proximity example in the nRF51 SDK as a starting point. The Proximity example utilizes the App timer, which uses SWI0 for processing, just like the rbc_mesh framework.

Integrating rbc_mesh with ble_app_proximity

The Proximity example is included as part of the nRF51 SDK (both version 6.x.x, 7.x.x and 8.x.x), and uses both the pstorage and app_timer modules. It also distributes Softdevice events with the Softdevice-handler. We will go through the process of including the rbc_mesh as part of this example, setting the stage for mesh-functionality with the Proximity example.

Step 1: importing the framework

First off, we need to move the rbc_mesh framework into the Proximity example project environment. The easiest way to do this is by moving the entire folder /nRF51/rbc_mesh/ into a top level /rbc_mesh/ folder in the Proximity example, and add an rbc_mesh-source-group to the project in Keil uVision, where you add all the source files in /nRF51/rbc_mesh/src/ (right click target in the Project explorer, press "Add Group…​". Right click the new group and press "Add existing files to…​"). Also remember to add an include-statement to your target for both /rbc_mesh/ and /rbc_mesh/include/ (Target options → C/C++ → Include paths…​). The rbc_mesh is now part of your project.

Step 2: Softdevice event handler

The rbc_mesh has to check for Softdevice events related to the Timeslot API in order to function. In the original framework, this is conducted in the function ts_sd_event_handler(void) in timeslot_handler.c. This function is not very considerate of other Softdevice related activities on the chip, however, and consumes the SD_events as they come. In order to overcome this, we can replace it with a more cooperative version. Delete the ts_sd_event_handler(void) function and all its references, and insert this function instead:

timeslot_handler.c
void rbc_mesh_sys_evt_handler(uint32_t evt)
{
    switch (evt)
    {
        case NRF_EVT_RADIO_SESSION_IDLE:
            break;

        case NRF_EVT_RADIO_BLOCKED:
            timeslot_order_earliest(TIMESLOT_SLOT_EMERGENCY_LENGTH, true);
            break;

        case NRF_EVT_RADIO_CANCELED:
            timeslot_order_earliest(TIMESLOT_SLOT_LENGTH, true);
            break;

        default:
            break;
    }
}

Then expose the function in the timeslot_handler.h header. This function should be called from the static void sys_evt_dispatch(uint32_t sys_evt) function in main.c, with sys_evt as parameter. This leaves the consumation of the event to the softdevice-handler, and other modules, such as pstorage won’t miss out on incoming system events.

Step 3: Picking up BLE events

The next step is also exhibited in the BLE_Gateway example in the framework: we need to get the BLE events from the Softdevice. This is necessary if we want the mesh to react to changes made to the Softdevice GATT server by external devices through a regular Softdevice connection, as the framework is unable to pull these events directly from the Softdevice without a little help.

All that is required for this step is to add this line to the end of static void ble_evt_dispatch(ble_evt_t * p_ble_evt) in main.c:

main.c
rbc_mesh_ble_evt_handler(p_ble_evt);

This passes the incoming BLE event to the framework, just as the example does with the other modules in the system.

Step 4: receiving framework events

In order to get feedback from the rbc_mesh, the application must implement void rbc_mesh_event_handler(rbc_mesh_event_t* evt) somewhere in the application space. See the examples under /nRF51/examples/ for implementations of this function.

Step 4: initialization

The final step is to initialize the rbc_mesh framework. First off, the framework calls sd_ble_enable() in mesh_srv.c. This is already done as part of the initialization in the Proximity example, and can be left out of the mesh_srv.c code. Remove the line calling the Softdevice function.

Finally, we must initialize the framework from the application. This is also displayed in the examples under /nRF51/examples/, but note that uint32_t rbc_mesh_init(rbc_mesh_init_params_t) must be called after ble_stack_init() in the application in order to secure correct behavior (more specifically, after sd_ble_enable()). We also recommend that you initialize the framework before you start advertising, to ensure that the application includes the mesh service in its GATT server for external devices.

The framework should now be completely integrated, and it should be possible to see the Mesh service with its characteristics along with the proximity services when you connect to the nRF51 with an external BLE device. Note that this approach is applicable for many other SDK examples as well, but that we can’t guarantee proper operation in all integration scenarios.