Relay Configuration and implementation in BLE mesh network

[Jeena Francis]

I am trying to implement the following: I have a mesh node built using the Sensor Server  example for publishing temperature data. I want one relay node to transmit the temperature data to another node, which is not within the radio range of the first node. This second node is built using the Sensor Client model. My question is: how do I implement the relay feature, which code should I use for that, and what changes need to be made?

[Hung Bui]

Hi Jeena, 

By default most of mesh sample has the relay feature enable. You don't have to do anything except from having CONFIG_BT_MESH_RELAY=y (by default in many samples)

If you don't want to have relay feature enabled, just set CONFIG_BT_MESH_RELAY=n in prj.conf

[Jeena Francis]

Do I need to make any changes in the BLE Mesh app?

[Hung Bui]

Hi Jeena, 

Jeena Francis said:

Do I need to make any changes in the BLE Mesh app?

 The relay role is also can be configured from the BLE Mesh app. You can access the configuration  server and turn off and on relay feature. (you would need to do a reload to load the current value before you change it)

Jeena Francis said:

Which element is configured, and do I need to set the publish and subscribe addresses, publish TTL, publish retransmission count, and interval?

As far as I know it's preconfigured. But you can change them in the configuration server (in the primary element) 

[Jeena Francis]

I want to send a custom message using a custom Property ID added to the Mesh Sensor observer example. How do I add a custom Property ID? Currently, I am using #define CUSTOM_ID 0x1234. The message is sent from the server side but does not trigger the callback on the client side. What changes need to be made?

[Hung Bui]

Hi Jeena, 
The new question is not related to the original one. I would suggest to create a new ticket. 

[Jeena Francis]

OK.Thank You 

[Jeena Francis]

Hi,

In the app, the relay setting is disabled. I have attached a image for reference.

[Hung Bui]

Hi, 
You need to connect to a mesh node before you can control that. 
Have you made sure CONFIG_BT_MESH_RELAY=y in the prj.conf  ?

[Jeena Francis]

I already connected to a mesh node and CONFIG_BT_MESH_RELAY=y is in the code 

[Hung Bui]

Hi Jeena, 
Please make sure it's still connected. When it's connected you should see the button say "Disconnect" not "Connect". Also you would need to load the role (read the configuration server) by pulling the screen downward (touch and pull down) 
The screen should look like this: 

[Jeena Francis]

Relay enabled successfully.
I have one Sensor Server node that publishes data to a group address, and one Relay node flashed with Sensor Client code. The Relay node is enabled as a relay in the application and is configured to publish and subscribe to the same group address. The last node is a Client node, also flashed with Sensor Client code and subscribed to the same group address used by both the Server and Relay nodes. However, the messages are not received by the Client node. The Relay node is placed between the nodes, but the messages are still not reaching the Client.
what changes need to be done for proper working.

[Elfving]

Hi Jeena, I'll take over this case for a bit as Hung is OOO currently.

First of all, that sounds like it 'should' be working, though the thing with Mesh or any "flooding network" is that it might require some tweaking to get working perfectly. If for instance the Sensor Client is just within reach of the relaying node, and not the other, and the SC node is not scanning with the radio that exact moment it needs to, then it will miss this message. With Mesh you could counter this by eg. increasing the publish retransmission count, or get more nodes within the range of the one you need to reach, or send a message that you want the receiving node to acknowledge, so that you know that it has been recieved. With a small test with 3 nodes, it looks like this is so simple that it should immediately work, though the simplicity of the set-up could ironically be the issue. You for instance would typically like a Mesh node to be within the range of a few others, not just one, to counteract this.

Though with that out of the way, I agree that what you have tried here should work the majority of the time. Does it always fail? Could you try increasing publish retransmission count? Make sure the TTL is high enough, the way TTL works can be a bit confusing (0 and 1 means the same etc.).

Regards,

Elfving