High sleep power consumption with onewire after migrating to 3.2.1

[sasodoma]

Hi,

I am developing a low power BLE device using Promicro nRF52840 boards. After updating to ncs3.2.1 I have noticed a high power consumption in sleep, that isn't present with ncs3.1.1. Reading the changelogs and migration guides I am unable to determine what exactly changed. I have put together a simple application that is enough to show a clear difference. When compiling with 3.1.1 the consumption of the whole board is 54 uA, while with 3.2.1 it's 1.4 mA.

I have previously successfully used the pm suspend to keep power low in sleep, but it seems it no longer works. I'm sure the fix is simple but I was unable to figure it out.

Here's the code:

main.c:

#include <zephyr/kernel.h>
#include <zephyr/pm/device.h>

static const struct device *uart = DEVICE_DT_GET(DT_NODELABEL(uart0));

int main(void) {
    pm_device_action_run(uart, PM_DEVICE_ACTION_SUSPEND);
    k_sleep(K_FOREVER);
    return 0;
}

prj.conf:

CONFIG_SENSOR=y
CONFIG_W1=y

CONFIG_LOG=n
CONFIG_SERIAL=n
CONFIG_CONSOLE=n
CONFIG_UART_CONSOLE=n

CONFIG_PM_DEVICE=y

promicro_nrf52840_nrf52840.overlay:

&uart0 {
	status = "okay";

	w1_0: w1-zephyr-serial-0 {
		compatible = "zephyr,w1-serial";
		#address-cells = <1>;
		#size-cells = <0>;
		status = "okay";

		ds18x20: ds18x20 {
			compatible = "maxim,ds18b20";
			family-code = <0x28>;
			resolution = <12>;
			status = "okay";
		};
	};
};

&pinctrl {
	uart0_default: uart0_default {
		group1 {
			psels = <NRF_PSEL(UART_RX, 1, 4)>;
			bias-pull-up;
		};
		group2 {
			psels = <NRF_PSEL(UART_TX, 1, 6)>;
			/* max. 5mA drive strength: */
			nordic,drive-mode = <NRF_DRIVE_H0D1>;
		};
	};

    uart0_sleep: uart0_sleep {
        group1 {
            psels = <NRF_PSEL(UART_TX, 1, 4)>,
                    <NRF_PSEL(UART_RX, 1, 6)>;
            low-power-enable;
        };
    };
};

Thank you in advance!

Best regards,

Sašo

[sasodoma]

I have bisected the difference to the commit https://github.com/nrfconnect/sdk-nrf/commit/c2eab60735568bb24788d3767a3b7f321a8a8360 

I'm guessing the actual difference is in the zephyr that got updated, but I'm having trouble building while trying to bisect the zephyr repo.

EDIT: I have managed to bisect the zephyr repo as well, and the commit that causes the problem is https://github.com/nrfconnect/sdk-zephyr/commit/b03b65a9b51ae869bd36fde687ec142e970660e0, which switches CDC ACM to the new USB device stack. I can lower the power consumption by setting CONFIG_CDC_ACM_SERIAL_INITIALIZE_AT_BOOT=n, but this disables it completely. I also tried suspending both the usbd and the cdc-acm but was unsuccessful:

static const struct device *usbd = DEVICE_DT_GET(DT_NODELABEL(usbd));
static const struct device *board_cdc_acm_uart = DEVICE_DT_GET(DT_NODELABEL(board_cdc_acm_uart));

...

pm_device_action_run(usbd, PM_DEVICE_ACTION_SUSPEND);
pm_device_action_run(board_cdc_acm_uart, PM_DEVICE_ACTION_SUSPEND);

How can I keep power consumption low in sleep without disabling USB CDC ACM?

[Ressa]

Hi  Sašo,

I just tried your code with different ncs versions including 3.2.1 on nRF52840 DK and I am getting around 10 uA average current in all of them. The current is just for SoC. The supply is connected externally using P21 connector. Not sure why you see different current. Do you have a DK to try on that as well? 

[sasodoma]

Thank you for the test. Is it possible that the difference is due to the DK not having USB CDC ACM enabled by default?

Unfortunately I do not have a DK with the nRF52840 to test, but I do have a different DK that I could use to program the ProMicro board as if it was a DK, to see if the difference is the default settings.

[Ressa]

Hi Sašo,

I think so. USB CDC‑ACM is not enabled by default on DKs. It seems like device power management is not implemented for USB CDC-ACM. So it will not work with pm_device_action_run() the same way as for example UART hardware peripherals. 

Please have a look at below case which is similar to your question:
(+) How to disable USB CDC-ACM during running - Nordic Q&A - Nordic DevZone - Nordic DevZone

Best regards,
Ressa

[sasodoma]

It seems that in the end Kentarou was able to reduce power consumption by suspending uart0, which is what I've been doing before the update and it doesn't work anymore. Given that this change was caused by a Zephyr update and is not directly nRF related, I will try to open an issue with them and see if someone can tell me what's to do in the new version. I will post the answer here if I get it.