Mesh low power current consumption

[Gerry]

Hi,

As discussed in this ticket we need a way to reduce the current consumption.

The LPN example doesn't solve this for us.

Our application is based on the light switch server example. After the node is provisioned, we would want to have the node in sleep mode with it's radio off and only RTC running to get down to approx. 4uA. 

When it wakes up on RTC or on an external interrupt it should be on to send a message and then sleep again.

Could you please provide some lines of code, how to get the node into this state?

using nRF52840 and Mesh SDK 3.1.0

Regards

Gerry

[Hung Bui]

Hi Gerry, 

What is your current average current consumption ? Note that depends on the Poll timeout, how often do you wake up and send/receive message, you may have different power consumption levels. 

Note that the sleep current of a LPN can get down to 3uA in our test here. 

Does your node need to receive data from other nodes ? or it only needs to send data ? 

[Gerry]

Hi Hung,

Our low power node needs to send data only. (for example once every 5 minutes)

The average current of the LPN is 40uA now (without changing the example). Where can we change the poll timeout and what functionality will it affect?

Since there seems to be no difference in average power consumption whether a friendnode is connected or not, we would be interested in having our light-switch-server based application to consume as little current as possible (without having a frindnode). I can not see, where this is made in the LPN-example. Our light-switch-server based application consumes 10mA at the moment.

Regards

Gerry

[Hung Bui]

The poll timeout is configured in the LPN example with POLL_TIMEOUT_MS. It's set to 10s by default, you can try to increase this. 

There are actually other options to do low power with mesh. One of them is just to simply put the device to sleep mode and wake up when need to send something. You can sleep for up to 96 hours. 
I attached here a slides we used in a conference in Bluetooth World 2018. Please have a look. This slides are not for redistribution. 

LowpowerMesh.pdf

[Gerry]

Thanks for that. The "Low duty cycle node" described in this document, is exactly what we want to achive.

We tried already, but in a mainloop like this:

    for (;;)
    {
        (void)sd_app_evt_wait();
    }

we always loop, meaning, the program comes out of sd_app_evt_wait() multiple times per second. I would expect, the program to stay in this function, until an external- or RTC-interrupt occurs. We already tried with nrf_mesh_disable() and scanner_radio_stop() but this didn't help.

Could you give us some lines of code, to see how this "Low duty cycle node" would be achived in the light switch server example?

[Hung Bui]

Hi Gerry, 

You would need to disable the mesh stack and put the device to sleep. When you wake up, you need to initialize the mesh stack again.

There is a bug in the stack that disabling it may take longer time that it should. You can follow this case: https://devzone.nordicsemi.com/f/nordic-q-a/43301/nrf_mesh_disable-function-changed-since-sdk-for-mesh-v3-1-0/180061#180061