Reduce power consumption from network core

[esmart-engineering]

My company is working on a project that uses the nRF53 that needs to wirelessly send out data roughly every 3ms (via ESB). We are now at the point where power needs to be optimized.

There seems to be promise in cutting back power in the nRF53's network core (see attached screenshots). When sending, our current draw is about 2mA, with about 1.6ms each time used to send the data out. From simply disabling the network core 1 time during runtime (by using nrf_reset_network_force_off()) and keeping it off, we see it is drawing about 1mA for 0.9ms each time. So roughly speaking, it looks like 2mA - 1mA = 1mA on average is used to keep the network core operating, and the time spent executing code in network core each time is 1.6ms - 0.9ms = 0.7ms.

• Sending normally (network core on)
  • 
• Sending with network core off
  • 

One method we tried is to turn off network core after each time data is sent, and turn it back on before the next data. However, that is presenting with timing problems. It is also being addressed in a separate ticket/forum-post.

For this ticket, I would like suggestions for what other methods that can be used (related to the network core) in order to cut back on power and bring the average as close to that 1mA as possible. For example, ways to put the network core to a lighter sleep that allows faster wakeup? ESB options that lower current draw? Configuration options exclusive to network core that could be drawing unneeded current? I'm open to whatever suggestions come to mind. Thank you in advance!

For context, my setup is using a Windows 10 machine, nRF5340DK, PPK2, NCS v2.5.0.

[Kazi Afroza Sultana]

hello,

Are these 

CONFIG_PM=y
CONFIG_PM_DEVICE=y enabled in config file?

[esmart-engineering]

I've added both those configs to my app core and net core, but it did not seem to change the results. I think CONFIG_PM_DEVICE=y usually needs to be paired with functions in the code that turn off (for example, like in NCS v2.5.0, zephyr\samples\subsys\pm\device_pm). Is there a function that can be used for disabling network core?

Any other things you can suggest?

[Kazi Afroza Sultana]

Hello, 

''The application core can force the network core off.

The application core can hold the network core in Force-OFF mode, using register NETWORK.FORCEOFF.

Application core resets implicitly result in the network core being held in Force-OFF. The network core will be held in Force-OFF until the application core releases it using the NETWORK.FORCEOFF register.''

https://docs.nordicsemi.com/bundle/ps_nrf5340/page/chapters/reset/doc/reset.html#ariaid-title8 

[esmart-engineering]

I have already done this, by using the function nrf_reset_network_force_off(). That's how I got the 2 sets of graphs above. But it does not seem usable for our purposes because starting the network core back up is too slow (see the "separate ticket/forum-post" I had already put in the original post).

Are there other ways besides the NETWORK.FORCEOFF option?

[Kazi Afroza Sultana]

Hello,

I am not sure if any unused peripheral is active in your application that causes high current. Do you have external LF crystal in your design? This can help reduce power consumption.  

There is a case about power consumtion on ESB (+) ESB power consumption - Nordic Q&A - Nordic DevZone - Nordic DevZone were turning off HFCL where there is no operation helped to reduce current consumption. Maybe you can look at this?