Put BLE Mesh node in deep sleep

[Rajendra]

Hi,

We are working on BLE MESH using nRF52840. We are trying to put nRF52840 into deep sleep mode. The deep sleep current is about 210 micro Amp. Further, the current is continuously increasing approx. by 1 micro Amp after every 60 sec.

My setup:
nRF SDK ver : nRF5_SDK_17.0.2_d674dde
BLE MESH ver : nrf5_SDK_for_Mesh_v5.0.0
Hardware : BT840 based custom board

The functions used for putting the nRF52840 into deep sleep -
nrf_mesh_disable()
nrf_pwr_mgmt_shutdown(NRF_PWR_MGMT_SHUTDOWN_STAY_IN_SYSOFF);

We also tried sd_power_system_off() but result are no better.

We are able to achieve deep sleep current of 500 nano Amp on same hardware, using Thread protocol. We are not sure how to achieve it using BLE Mesh.

It would be a great help if you could suggest a solution or give us a direction.

Kind Regards,
Rajendra

[Hung Bui]

Hi Rajendra, 

I tried to reproduce the issue here but I couldn't see it. 
Attached you will find the project I modified light_switch to enter deep sleep mode. 
It worked in both cases before and after provisioned. 

I attached the video when I tested here. You can see that when I pressed button 0 , I will call this: 

		bt_mesh_prov_disable(BT_MESH_PROV_GATT | BT_MESH_PROV_ADV);
        bt_mesh_suspend();
        nrf_power_system_off(NRF_POWER);

And the current consumption went down to about 2uA. The example is from NCS v2.1.2

3107.light_switch_sleep.zip

My suggestion is to get hold of a DK and use it as the reference. 

[Hung Bui]

PS: After further testing I found that I also got 200uA. But only when the serial port is open. 
Could you try to test with 

CONFIG_SERIAL=n

 in prj.conf ? 

if you still need logging, I think we need to disable UART before enter sleep mode. 

Or you can use RTT for logging but you also need to disconnect RTT if you want to have low power consumption. . 

[Rajendra]

Hi,

We are able to achieve deep sleep current on DK board. It came down to ~18.5 uA. Now we trying current measurement on BT840 based custom board. The difference between your current measurement setup and ours is - 

• We are using DK H/W ver 2.0.1 2020.38 and you are using DK HW ver 1.0.0
• We are taking a hard reset before current measurement. Are you also taking a hard reset?

One interesting thing we noticed, when we download the firmware and do not take hard reset, the deep sleep current measured is ~3.3 uA. But when we take a hard reset after download, deep sleep current is ~18.5 uA.

Thank you for your quick support. We will now checking this on our BT840 based custom board.

[Hung Bui]

Hi Rajendra, 

Thanks for the information. Have you found why it was around 200uA before with your code ? 

Regarding the issue with 18.5uA. How did you measure the current consumption ? Did you use a multimeter ? Could you try to measure the current with a PPK2 ? 

Could you explain which hard reset you used ? Was it a power reset or pin reset ? 

When you see the current consumtion to 18.5 uA , could you try calling "nrfjprog -r" to trigger a soft reset ? and check if the current consumption when entering system off still the same or go down to 3.3uA ? 

I would suggest to try testing on other board as well because the DK has a programmer chip on it and may cause extra current. 

[Rajendra]

Hi,
In earlier trials we never tried it on DK board. We were always checking it on custom board. 225 uA was observed on custom board.
We used multimeter to measure current on DK board that came to 18.5 uA. We also have advanced current meter where we can see the current value on waveform.
We are not using PPK2 kit since we have advanced current meter but definitely it would be one of the best options to measure the current.
We used power reset to hard reset the board.
We have not used nrfjprog -r to trigger soft reset, will check it.