Power Consumption of nRF5340

[Michael Nemanov]

Hi,

I'm evaluating the new nRF5340-PDK and trying to put the device in low power mode. My steps so far:

1. Cut SB40 to allow measuring current via P22.
2. Connect power measurement equipment to P22.
3. Build an example application from the SDK with the command

   west build -b nrf5340_dk_nrf5340_cpuapp

4. Program the binary via the command

   nrfjprog -f NRF53 --eraseall
   nrfjprog -f NRF53 --program <example path>\build\zypher\\zephyr.hex

5. Reset the board via SW5.

The examples are built and programmed successfully (I can see the expected prints on UART).
However, I do not see any significant current changes when the applications are active or idle. My highest measurement is 3.40mA while the lowest is 3.28 mA.
I've tried using the zephyr\samples\subsys\power\device_pm and nrf\samples\nfc\record_text samples, both with the same results.

Am I missing some configuration during the build phase? Should I add some code to put the system into low power mode explicitly? I would have expected it to happen implicitly by the kernel once there are no active tasks.

Thanks,
Michael.

[Håkon Alseth]

Hi Michael,

 

This line:

https://github.com/NordicPlayground/fw-nrfconnect-zephyr/blob/master/boards/arm/nrf5340_dk_nrf5340/nrf5340_cpunet_reset.c#L55

Will release the network CPU, and if there's no program in the network core, it'll just run, causing a higher power consumption.

You can either put the core back to sleep, or compile a simple program that goes straight to wfe (or k_cpu_idle() when using the rtos API).

If you go to ncs/zephyr/samples/basic/blinky/ and modify the main.c to hold only "while(1) k_cpu_idle();" and build/flash for the network core:

west build -b nrf5340_dk_nrf5340_cpuapp

 

Could you try this and see if the current goes down?

Note that since you have UART output, you should see approx. 0.5 mA current consumption due to the UART RX being active. if you disable serial (CONFIG_SERIAL=n), it should go lower.

 

Kind regards,

Håkon

[Michael Nemanov]

Hi Håkon,

Thanks for the quick reply

So assuming I have no code I want to run in the network core I could do:
NRF_RESET->NETWORK.FORCEOFF = RESET_NETWORK_FORCEOFF_FORCEOFF_Hold;
from the application CPU and it will put the network core to sleep?

Regards,
Michael.

[Håkon Alseth]

Hi Michael,

 

Michael Nemanov said:

So assuming I have no code I want to run in the network core I could do:
NRF_RESET->NETWORK.FORCEOFF = RESET_NETWORK_FORCEOFF_FORCEOFF_Hold;
from the application CPU and it will put the network core to sleep?

That is correct. Remember to power cycle the nRF after programming, so that the debugger session is guaranteed to be closed (and MCU is not halted)

 

Kind regards,

Håkon