52840 ncs mesh question

[Carey]

hi,  customer use nrf52840 made mesh node. use nrf connect SDK v1.6. they have two quetion.

1:   How to set 125kb low speed and long rang in BT mesh network,

2:   How to enable low power mode in the SDK, do we have any low power mode exmple in the SDK?

[tesc]

Hi,

1: Bluetooth mesh builds on Bluetooth 4, and does not have long range / coded phy. This is per Bluetooth mesh specification.

2: You can configure a node to be a Low Power Node, through the configuration setting CONFIG_LOW_POWER=y. The LPN feature will then be available, and enabled on startup by default. You can then also turn it off and on when you want to, runtime, using bt_mesh_lpn_set().

Regards,
Terje

[tesc]

Hi,

A small update: There are no examples in the SDK where LPN is enabled, but for all examples you can enable LPN the way I described. Friend feature is enabled by default in all examples, so as long as you have a non-LPN node in the network the LPN node should be able to find a friend for keeping and relaying the incoming messages.

Regards,
Terje

[Patrickcyc]

Hi Terje,

I tried to enable the setting of "Support for Low Power features" <BT_MESH_LOW_POWER> in NCS mesh light switch example, it can enter into LPN mode with low current consumption. I found the light on/off publication can send to light node immediately, however , the light on/off subscription from light node is received over 10 seconds. I tried to change "Receive delay requested by local node" <BT_MESH_LPN_RECV_DELAY> from 100 to 10 , but it does not have much improvement of receiving time. How can change the setting that make the LPN polling the cached message from friend node faster?

Thanks

Patrick

[Hung Bui]

Hi Patrick, 

I assume it takes longer to receive the status message send from light server to the light switch LPN, correct ? 
It's because if you don't proactively poll the friend node it will only poll it to avoid friendship termination. This is why you only receive the packet from the server after average 10 seconds. 

What you need to do is define a timer and in the timer handler you call bt_mesh_lpn_poll(). This will periodically poll the friend node if there is any message for the LPN node. 
Of course the drawback of calling bt_mesh_lpn_poll() too often is that you will consume more current.