Low power BLE advertising with Zephyr on nrf52840, is it supported?

Question

I'm using the NRF52840-DK with the SB40 jumper cut, then powering through P21 and measuring with an ammeter across P22. USB is unplugged during measurement. I'm using zephyr with ncs v1.2.0.

I have built the samples/boards/nrf/system_off example and I was able to get about 400uA of current draw. By modifying the example to include CONFIG_SERIAL=n I was then able to get roughly 3uA. I have since tried to modify that example to include bluetooth advertising, but I can't get the current draw below 1.3mA. Here is my code:

#include <zephyr.h>
#include <device.h>
#include <power/power.h>
#include <bluetooth/bluetooth.h>
#include <hal/nrf_gpio.h>

/* 1000 msec = 1 sec */
#define SLEEP_TIME	1000


/* 1000 msec = 1 sec */
#define SLEEP_TIME	1000

#define BT_LE_ADV_CONN_NAME_SLOW BT_LE_ADV_PARAM(BT_LE_ADV_OPT_CONNECTABLE | \
					    BT_LE_ADV_OPT_USE_NAME, \
					    BT_GAP_ADV_SLOW_INT_MIN, \
					    BT_GAP_ADV_SLOW_INT_MAX)

static u8_t mfg_data[] = { 0xff, 0xff, 0xAB };

static const struct bt_data ad[] = {
        BT_DATA(BT_DATA_MANUFACTURER_DATA, mfg_data, 3),
};

void main(void)
{
    u32_t cnt = 0;
    sys_pm_ctrl_disable_state(SYS_POWER_STATE_DEEP_SLEEP_1);

    int err = bt_enable(NULL);
    if (err) {
        printk("Bluetooth init failed (err %d)\n", err);
        return;
    }

    err = bt_le_adv_start(BT_LE_ADV_CONN_NAME_SLOW, ad, ARRAY_SIZE(ad),
                          NULL, 0);
    if (err) {
        printk("Advertising failed to start (err %d)\n", err);
        return;
    }

    while (1) {
        cnt++;

        k_sleep(SLEEP_TIME);
    }
}

and prj.conf

CONFIG_GPIO=y
CONFIG_OPENOCD_SUPPORT=n
CONFIG_ASSERT=y

CONFIG_BT=y
CONFIG_BT_BROADCASTER=y
CONFIG_BT_DEVICE_NAME="Zephyr Test"

CONFIG_SYS_POWER_MANAGEMENT=y
CONFIG_SYS_POWER_DEEP_SLEEP_STATES=y
CONFIG_SYS_PM_STATE_LOCK=y
CONFIG_SERIAL=n

The advertising itself appears to work fine. Is this low power advertising supported? If so, could you please tell me what I am missing here?

Håkon Alseth · Accepted Answer

Hi, 
 
 Thank you for providing sample code and configuration, compiled out-of-the-box. 
 I cannot see that you are missing any settings. 1.3 mA is high. Are you connecting with the debugger? That normally gives a bit higher current consumption on nRF52840 (around 1.6 mA). If I do not power cycle or reset the device after programming (ninja flash), I see approx. 1.37 mA. Could this be the issue? 
 I took the samples/bluetooth/peripheral_dis, pasted your code into main.c, and added these to prj.conf: 
 CONFIG_SYS_POWER_MANAGEMENT=y
CONFIG_SYS_POWER_DEEP_SLEEP_STATES=y
CONFIG_SYS_PM_STATE_LOCK=y
CONFIG_SERIAL=n 
 
 After power cycling (or issuing a "nrfjprog --reset"), this behaves as expected when testing with nRF52840-DK (SB40 cut), with the lowest power consumption is approx. 4 uA, and throttles higher once per second, per the advertising interval you set. 
 
 Kind regards, 
 Håkon

Low power BLE advertising with Zephyr on nrf52840, is it supported?

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