Mouser Bluetooth Mesh: L3 Making a Light Switch Using the Example Code

How To Design With Bluetooth Mesh


You can "git" a workspace will all of these files at https://github.com/iotexpert/MouserVTWBluetoothMesh or git@github.com:iotexpert/MouserVTWBluetoothMesh.git

Summary

In the first several lessons I showed you how to build a BLE Mesh Network using the Cypress Android App and the Windows Application.  I don’t know about you, but even though I live twenty years back in time in Kentucky I still have light switches.  In this lesson Ill show you how to add a light switch to your network.  And then we will have a good look a the code because we have run enough demo projects.

Given that I have a working network from the last lesson I will just add the switch to that network.  Meaning, I will use the Mesh Client to provision in the new switch.

For this exercise we will:

  1. Create the VTW_MeshOnOffSwitch Project
  2. Provision and Configure the Switch
  3. Firmware Architecture
  4. Examine the Code

Create the VTW_MeshOnOffSwitch Project

Start a new project with File–>New–>ModusToolbox IDE Application

Pick out the CYBT-213043-MESH hardware.

I will use the BLE_Mesh_OnOffSwitch starter application.  Notice that I named it “VTW_Mesh_OnOffSwitch”

Now press Finish to create the application in your workspace.

Now your Project Explorer should look like this.  Notice that in the quick panel there are the launches for this application.

So, press “VTW_MeshOnOffSwitch Build + Program”

Provision and Configure the Switch

Go back to the Mesh Client application.  Just as before you can add the Switch to the network by scanning for unprovisioned BLE Mesh Nodes.  When the node shows up, give it a name of SW1 and then press “Provision and configure”

After a while, your trace window will indicate success via the ever informative “done” message.

If you have a serial terminal attached to the development kit you will see what happens during the provision/configuration process.

Now test the button on your new Light Switch and notice that both LEDs turn on (both Dimmable and L2).  You can configure the Switch to control only L2 if you want.  On the “Use Device” drop down pick “SW1 (0004)” then select control “ONOFF” and pick the switch “L2”.

After applying the change you can see that switch only controls L2.  You can then switch it to “Dimmable” to control the other LED.

Firmware Architecture

Examine the Code

A Cypress Bluetooth Mesh project has several basic sections  Specifically you must configure:

  1. Elements & Models
  2. Mesh Config
  3. Application Function Pointers
  4. mesh_app_init

Plus for the switch application, you will need to configure the button management code (what happens when the button is pushed).

    Elements and Models

    The “Element” is a fundamental unit of thingness in a BLE Mesh.  For instance in the projects we have looked at, the LEDs are represented by an Element, and the switch is represented by another element.  Each element will have one or more models that represent the functionality of the element.  For instance, in a switch you will have a “WICED_BT_MESH_MODEL_ONOFF_CLIENT”.   If you look at on_off_switch.c you will see that we first define an array of models.  Then we define an array of elements.  The array mesh_element1_models will be associated with the the first element.

    Mesh Config

    The mesh config structure handles the basic setup for the Cypress Bluetooth Mesh.  This structure is loaded in by the stack when it starts.

    Application Function Pointers

    The Bluetooth Mesh stack interacts with your program via functions that it runs when something is happening.  You can either accept the default behavior, or you can write your own function.

    mesh_app_init

    The function mesh_app_init is called by the stack when the stack starts.  It is your opportunity to get things going.   In the “if” we setup information which makes it easier to see what is happening when you provision by adding that information to the scan response packet.

    The last thing we do in mesh_app_init function is initialize the onoff client model. This should be done for any models that your device uses. The model initialization functions can accept the name of a function that we want the stack to call when it receives messages from the network for that model. In this case, we don’t need to do anything in our firmware for onoff client messages, so we specify NULL.

    Button Management Code

    Now you just need to setup the button hardware in the mesh_app_hardware_init function to generate an interrupt when the button is pressed or released..

    The interrupt handler will call the function wiced_bt_mesh_model_onoff_client_set to publish the button pressed message.