nRF52840 current consumption in System ON and active modes of operation

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Wed, 13 Sep 2023 08:50:37 GMT

Just wanted to share an update with you. When using VDD = 3.0V instead of VDD = 1.8V, we were able to get a current consumption value of ~3.3mA in CPU active mode:

What I measure on my side with the 1.1.0 hardware version of the nRF52840-DK is ~3.7mA

What has been measured by my colleagues with 3.0.1 hardware version of the nRF52840-DK is ~3.3mA

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Tue, 12 Sep 2023 12:04:50 GMT

I can measure the same as you when doing this simple code:

#include <zephyr/kernel.h>

int main(void)

{

while(1);

}

CONFIG_BOARD_ENABLE_DCDC=y

CONFIG_BOARD_ENABLE_DCDC=n

I will check internally what may be the problem here.

Kenneth

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Mon, 11 Sep 2023 15:22:16 GMT

Hello, Kenneth.

I did not have any multimeter at my disposal so I decided to make the current consumption measurement using the Otii Arc tool instead of PPK II.

In order to stay longer in CPU active mode, I modified the sample application the following way:

RTC timer will wake up the CPU every 5 seconds
When awake (in CPU active mode), the CPU will stay in active mode until the Button_1 on nRF52840-DK is pressed

Find attached the new application code below. What I get for the current consumption in CPU active mode is the same as before:

Regards,
Bojan

devzone.nordicsemi.com/.../0820.main.c

devzone.nordicsemi.com/.../51437.prj.conf

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Wed, 06 Sep 2023 07:49:29 GMT

You put the multimeter in ampere mode, to measure current. Normally you do it like this:
https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/hw_measure_ampmeter.html

But if you are using PPK2 to supply power, then something like this:

Kenneth

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Wed, 06 Sep 2023 06:51:57 GMT

Should I measure the voltage across the pins of P22? Should I solder some shunt resistor on R90 before doing voltage measurements?

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Tue, 05 Sep 2023 12:25:07 GMT

Good point, can you add a regular multimeter on P22 (while being powered from PPK2) for comparison?

Kenneth

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Tue, 05 Sep 2023 12:10:43 GMT

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/444487"]Can you try to measure with a regular multimeter on P22 instead for comparison?[/quote]

If we use a regular multimeter on P22 from where we are gonna supply the CPU?
When using PPK II, it is configured in source mode - we give a 1.8V power supply through the same pin while measuring current consumption.

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Tue, 05 Sep 2023 11:26:32 GMT

Can you try to measure with a regular multimeter on P22 instead for comparison? Maybe also increase the duration to several seconds also for comparison.

Kenneth

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Tue, 05 Sep 2023 10:04:32 GMT

Hello, Kenneth

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/444448"]How are you measuring the active current here exactly? Are you measuring the max current or the average over some time? [/quote]

What I'm measuring is the average current over the time the CPU is active.

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/444448"]Can you share some PPK plots that we can look at (with a description of what is running and configuration)?[/quote]

Below you can find the PPK II screenshots measuring the current consumption when the CPU is in active mode. If you analyze the code I shared here in my initial post, you will see that the CPU is normally in System ON mode waking up every 3 seconds with the kernel/RTC timer and doing the following:

/* ... do processing */
printk("Hello World! %s\n", CONFIG_BOARD);
for(uint32_t i = 0; i < UINT16_MAX; i++){
    ++active_cnt;
}

What we are measuring as current consumption is the average current in active mode.

Here are the PPK II screenshots:

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Tue, 05 Sep 2023 09:29:27 GMT

Hello,

How are you measuring the active current here exactly? Are you measuring the max current or the average over some time? If you are measuring max current you could be measuring peaks and noise that is not directly from the CPU current.

Can you share some PPK plots that we can look at (with a description of what is running and configuration)?

Kenneth

RE: nRF52840 current consumption in System ON and active modes of operation

bojan — Mon, 04 Sep 2023 10:26:10 GMT

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/443729"]I guess in your example project you are only using a single-thread so it may work, but I mention it in any case.[/quote]

Yes, we are using a simple single-threaded sample application.

We could simplify our sample application and use the k_msleep() API instead of calling k_cpu_atomic_idle():

while(1){
   /* Do some work here. CPU will be in Active mode */
   
   /* Sleep in order to set the CPU in System ON mode */
   k_msleep(3000);
}

However, this did not change measured current consumption.

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/443729"]

In terms of running with or without DCDC this is controlled through the following two kconfig options:

CONFIG_BOARD_ENABLE_DCDC=y/n
CONFIG_BOARD_ENABLE_DCDC_HV=y/n

[/quote]

Thanks for that info. Even if we enable/disable DC/DC converter through the Kconfig options instead of explicitly changing the registers with NRF_POWER->DCDCEN0 and NRF_POWER->DCDCEN the current consumption in the CPU active state did not change.

[quote userid="2111" url="~/f/nordic-q-a/103290/nrf52840-current-consumption-in-system-on-and-active-modes-of-operation/443729"]Make sure to power cycle the board (nRF52840 in specific) after programming and before performing any current measurements.[/quote]

We power-cycle the nRF52840-DK board after programming because we need to change the position of some switches on the nRF52840-DK before we make the current measurements.

Would you mind using the code we shared with you and do the current measurements on your side?
What we are missing in our application in order to get ~3.3mA current consumption in the Normal Voltage mode with DC/DC regulator enabled?

Thanks in advance.

Sincerely,
Bojan.

RE: nRF52840 current consumption in System ON and active modes of operation

Kenneth — Wed, 30 Aug 2023 12:27:38 GMT

Hello,

Not sure if you have done it already, but I recommend to run through the devAcademy (and Lesson 7) if you haven't already:
https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/

You should not be calling k_cpu_atomic_idle or k_cpu_idle api directly, it should only be the idle thread responsible to enter sleep when there is no other work to do. This is also written in the documentation:

"In a regular system, the idle thread should be the only thread responsible for making the CPU idle and triggering any type of power management. However, in some more constrained systems, such as a single-threaded system, the only thread would be responsible for this if needed."
https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/zephyr/kernel/services/scheduling/index.html#c.k_cpu_idle

I guess in your example project you are only using a single-thread so it may work, but I mention it in any case.

In terms of running with or without DCDC this is controlled through the following two kconfig options:

CONFIG_BOARD_ENABLE_DCDC=y/n
CONFIG_BOARD_ENABLE_DCDC_HV=y/n

You can find they are by default enabled for the nRF52840DK board files here:
https://github.com/nrfconnect/sdk-zephyr/blob/main/boards/arm/nrf52840dk_nrf52840/Kconfig

Make sure to power cycle the board (nRF52840 in specific) after programming and before performing any current measurements.

Best regards,
Kenneth