ZigBee + FreeRTOS example power consumption optimization

[naps]

Hi, I'm using nrf52 dk and struggling to get low power consumption using multi_sensor_freertos ZigBee example from nrf sdk. Can you provide me some guides on how to optimize it? The lowest I can get is 600uA, which in my case is unacceptable. I was trying to add ZigBee dependencies to compile with blinky rtc example, but still after radio start-up i've got more than 0.5mA.

[Susheel Nuguru]

Hi Adam,

This example is not written correctly to be very power efficient.

The Tickless IDLE in FreeRTOSConfig.h file has been disabled. So the MCU is woken up every 1ms to service the RTC interrupt for maintain the freertos internal tick.

It is also using nrf_pwr_mgmt which contradicts the idle sleeping cycles. I think this example

• needs to enable the tickless idle, 
• nrf_pwr_mgmt_run needs to be removed and 
• zb_osif_go_idle in main.c needs to yield in a proper way so as to let the idle task to suspend the chip properly.

I need more time to re-calibrate this example to work properly with freertos (power consumption wise)

[Susheel Nuguru]

Hi Adam,

I see that there is something inside the zigbee stack that is wakinig the chip every 15ms even though I modified the example to unplug it from nrf_pwr_mgmt and use tickless idle.

I created a JIRA issue to ask the Zigbee engineers to take a look of what is making the chip wake up every 15 ms since it is not due to any peripheral that the application is in control of.

For your reference the internal ticket id is KRKNWK-6803.

Most of the engineers are on summer holidays so mostly there will be some delay before they can respond to it.

[naps]

Hi!
Any news on that topic? I would be grateful for some help.
I was doing the same things as you mention in your previous post, but with no luck to optimize power consumption.

[Edvin]

Hello,

Sorry. Susheel has been out of office. I checked the internal ticket (KRKNWK-6803), and it doesn't look like the FreeRTOS port in Zigbee is power optimized, and it doesn't look like there are any plans to develop it further. All our zigbee development resources are targeted towards the Zephyr implementation on Zigbee (which is an RTOS implementation). 

FYI: The reply on the internal ticket says this, among other things:

"I'm almost certain that it is the ZBOSS timer (beacon interval is approx 15ms) waking up the application. In order to suspend the task, while the timmer is disabled, you have to implement ZB_COMMON_SIGNAL_CAN_SLEEP ZBOSS signal handler. Otherwise you are simply leveraging only the ZBOSS IDLE state, not the ZBOSS SLEEP state (more information can be found here).

For som guidance and ideas how to implement this, it might be good to look at the OSIF implementation in NCS[Zephyr implementation]:

- The CAN_SLEEP handler: https://github.com/nrfconnect/sdk-nrf/blob/7a8861f03674ca0cf2f859de8ebbfebbfa0581ad/subsys/zigbee/common/zigbee_helpers.c#L455

- The sleep routine (will be called by zb_sleep_now()): https://github.com/nrfconnect/sdk-nrf/blob/7a8861f03674ca0cf2f859de8ebbfebbfa0581ad/subsys/zigbee/osif/zb_nrf_pwr_mgmt.c#L30

- The poll function: https://github.com/nrfconnect/sdk-nrf/blob/7a8861f03674ca0cf2f859de8ebbfebbfa0581ad/subsys/zigbee/osif/zb_nrf_platform.c#L501

The signaling mechanism is used to wake up ZBOSS task by other tasks that want to send something over Zigbee, as well as to wake up the ZBOSS task earlier than the sleep period, passed to the sleep function as an argument.

Best regards,

Edvin