nrf52840 System Idle Current Too High

RE: nrf52840 System Idle Current Too High

Mark J — Thu, 21 Nov 2019 01:14:06 GMT

I setup GPIO as requried and then found that the issue was actually related to my incorrect sleep of the accelerometer. Left the floating GPIO inputs init as input with pullup as this is good practice from what I have read online.

Down to approx 10 uA and most of that is for a sleeping accelerometer.

Tx for the help.

Mark J

RE: nrf52840 System Idle Current Too High

Kenneth — Wed, 20 Nov 2019 18:40:37 GMT

Default mode is low power yes.

Kenneth

RE: nrf52840 System Idle Current Too High

Mark J — Wed, 20 Nov 2019 18:28:47 GMT

Understood on the BLE peripheral examples. I will assume that the example that I used as a template is ok (from a low power perspective).

I had tried adding the following code - in an effort to get the power down:

err_code = sd_power_mode_set(NRF_POWER_MODE_LOWPWR);
APP_ERROR_CHECK(err_code);

Should that be put within init code (within main.c) to ensure low power mode? If it is there - I suppose it cannot hurt. Please confirm. Note that this code is not in the Nordic examples that I have seen, so I assume that it is not required, but I would like to confirm.

I will work with my hardware engineer to enable a pullup or pulldown as required on all inputs and outputs.

Thanks,

Mark J

RE: nrf52840 System Idle Current Too High

Kenneth — Wed, 20 Nov 2019 17:46:09 GMT

I believe most BLE peripheral have low idle current as long as LEDs and UART (logging) is not enabled. What version of the nRF52840 DK kit are you using?

Floating input pins can draw excessive current of several hundreds of uA if not connected to logic level.

RE: nrf52840 System Idle Current Too High

Mark J — Wed, 20 Nov 2019 16:53:23 GMT

Hi Kenneth,

I had reviewed the page that you linked and I have followed all recommendations in that link.

We only have 2 other GPIOs that are floating and may be contributing to some extra current, but my hardware engineer suggests that this contribution will be < 10 uA.

Is there any way for another peripheral to use current - even if I have not initialized it? My source code is derived from another Nordic example - Heart Rate Service under ble/peripheral. This source included many software components and peripherals that I am not using (e.g. peer_manager.h, nrfx_uart.h, etc). Even if I do not initialize these elements - is there any way for them to contribute to a current draw when compiled into a project? I cannot imagine how, but thought that I would ask.

Perhaps another approach is for me to re-create my SES project using an example that demonstrates low power "out of the box"? I can slowly introduce my required elements (e.g. SPI Master) to this example and monitor power at each step. Is there such an example?

Thanks in advance.

Mark J

RE: nrf52840 System Idle Current Too High

Kenneth — Wed, 20 Nov 2019 12:49:20 GMT

You may check out this in general:
https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/optimizing-power-on-nrf52-designs

You may also check if there is any floating GPIO's and/or internal pull-ups enabled that is is pulled-low etc.