The current is about 500uA when nrf52840 in idle mode

RE: The current is about 500uA when nrf52840 in idle mode

Stian Røed Hafskjold — Fri, 14 Oct 2022 11:08:34 GMT

Hi, I was wrong with SB22, it is for another DK version. You need to cut SB40. I'm very sorry. This is where it is located:

This must be cut in order to disconnect VDD_nRF (which you are powering with the yellow cable), from VDD (which is powered from USB).

I also see that the "nRF power switch" on your board is put to the Lo-Po position. This must be set to the default VDD position.

About the CONFIG_SERIAL=y, and 600 uA, in order to both use the UART and get low power consumption, you either need to implement the "low power UART" driver, or you need to dynamically turn on and off the UART in the application using the device power management API.

There is a blog post about power management in Zephyr here: Optimizing Power on nRF5340 SoC Designs

Best regards,
Stian

RE: The current is about 500uA when nrf52840 in idle mode

Anroll — Fri, 14 Oct 2022 08:05:17 GMT

Update

This issue can be solved by take-off DMA from uart.

I can get 5uA on my EVK.

I think the root cause is the DMA influence the ZEPHYR_CONSOLE uart letting the uart module can't be suspended.

RE: The current is about 500uA when nrf52840 in idle mode

Anroll — Fri, 14 Oct 2022 06:12:56 GMT

My condition seem be same with this Easy DMA issue. Didn't this issue be fixed on NCS 2.1.0 ?

devzone.nordicsemi.com/.../uninitialising-libuarte-does-not-turn-off-easydma-causing-high-current-draw-in-sleep

RE: The current is about 500uA when nrf52840 in idle mode

Anroll — Thu, 13 Oct 2022 14:17:36 GMT

Update:

After I add the CONFIG_SERIAL = n to my prj.conf file, the current can drop to 5 uA.

But, if I set the CONFIG_SERIAL=n, all uart will be disabled. (uart0/uart1)

Is there any way to let the current drop under 10uA and keep CONFIG_SERIAL=y simultaneously?

Because uart is a mandatory interface on our device.

#Note : I also try the pm_device_action_run(cons, PM_DEVICE_ACTION_SUSPEND) and it didn't improve the power consumption.

RE: The current is about 500uA when nrf52840 in idle mode

Anroll — Wed, 12 Oct 2022 02:50:52 GMT

Thank you for your reply. I tried the SMU setup on nrf52840dk based on the blog step.

But the current seems still as high as I used external power measuring. (about 500uA)

Below was my setup.

I also cut off the SB22 but it didn't improve the power consumption

Do I need to do anything on SW when the system enters idle mode?

RE: The current is about 500uA when nrf52840 in idle mode

Stian Røed Hafskjold — Tue, 11 Oct 2022 12:03:52 GMT

Hi, if you attach the Otii to the external supply header you will measure the current to the whole DK, including the debugger chip. Please have a look at this blog post on how to measure current on the DK (the blog is for nRF91 DK but it should be similar for the nRF52840 DK):

Getting started with current measurements on the nRF9160

Since the Otii is an source measurement unit (SMU), you will have to use the SMU setup described in the blog. You also need to cut the SB22 solder bridge on the nRF52840 DK. And set the output voltage on the Otii to match the VDD voltage on the DK (3V), in order to avoid leakage current through the SWD lines.

RE: The current is about 500uA when nrf52840 in idle mode

Anroll — Tue, 11 Oct 2022 05:49:05 GMT

1. I'm sure there are no other peripherals attached to the board. Below is the board I used.

2. I use OTII to power the dk board and measure the current. Do I need to do other settings on dk board?

3. Yes, I used the config file from the example and didn't do any changes to them. I only modify the main.c at 2 places.

(1) change pm_state_force(0u, &(struct pm_state_info){PM_STATE_SOFT_OFF, 0, 0}) to pm_state_force(0u, &(struct pm_state_info){PM_STATE_STANDBY, 0, 0})

(2) Add a return in main function to let main thread be suspended. (Make sure system enters idle thread)

#Note : I also try the pm_state_force(0u, &(struct pm_state_info){PM_STATE_SOFT_OFF, 0, 0}) on dk board and the current can successfully drop to 5uA as picture shown. But the system_off state didn't meet our need. We just need the system enter idle mode. (system sleep ON mode)

RE: The current is about 500uA when nrf52840 in idle mode

usmanmehmood55 — Tue, 11 Oct 2022 05:11:52 GMT

1- Are you sure you don't have any other peripherals attached to the board?

2- Did you follow the guide provided by Nordic about making modifications to the board to measure the current using PPK

3- Are you using the config file from the example? Or have you changed it in any way?