High power consumption of softdevice

[Elias Löwe]

Hello!

I am working on firmware for device that has freertos in the base and implements BLE beacon and 1 service with 7 characteristics. Everything works. But power consumption is too high.

After plenty of tests on final HW, I've created playground based on ble_app_hrs_freertos_pca10040_s132 sample project and switched to sparkfun board.

When have just FreeRTOS with no user-defined tasks, consumption is about 1uA.

After I call  ble_stack_init with code below, I got about 500uA. It is without advertising at all.

static void ble_stack_init(void)
{
    ret_code_t err_code;

    err_code = nrf_sdh_enable_request();
    APP_ERROR_CHECK(err_code);

    // Configure the BLE stack using the default settings.
    // Fetch the start address of the application RAM.
    uint32_t ram_start = 0;
    err_code = nrf_sdh_ble_default_cfg_set(APP_BLE_CONN_CFG_TAG, &ram_start);
    APP_ERROR_CHECK(err_code);

    // Enable BLE stack.
    err_code = nrf_sdh_ble_enable(&ram_start);
    APP_ERROR_CHECK(err_code);

    // Register a handler for BLE events.
    NRF_SDH_BLE_OBSERVER(m_ble_observer, APP_BLE_OBSERVER_PRIO, ble_evt_handler, NULL);
}

When beacon is enabled I have cca 650uA.

When GATT and beacon are working I have cca 750uA.

I measure with multimeter.

Results seems fine for me except for those 500uA after stack is initialized. Why is it so high? What can I do to lower it?

• SDK v 15.0
• NRF_LOG_ENABLED is 0
• Using RELEASE configuration.
• Tried S132 and S140 - result is the same

[Elias Löwe]

Unfortunately with NRF_LOG_ENABLED  and NRF_LOG_UART_BACKEND_ENABLED set to 0 I still have same consumption around 900uA  with ble_app_hrs_freertos_pca10040_s132 example

[Susheel Nuguru]

I think i found the problem.

It is in port_cmsis_systick.c

#if 0  // With FreeRTOS sd_app_evt_wait increases power consumption with FreeRTOS compared to _WFE (NRFFOSDK-11174)
#ifdef SOFTDEVICE_PRESENT
            if (nrf_sdh_is_enabled())
            {
                uint32_t err_code = sd_app_evt_wait();
                APP_ERROR_CHECK(err_code);
            }
            else
#endif
#endif // (NRFFOSDK-11174)

I do not remember the exact way i came to a conclusion that sd_app_evt_wait was consuming more power with freertos. Hence I created an internal ticket NRFFOSDK-11174 to investigate why this happened. I remembered that i was reading more power with freertos and using sd_wait function. While using WFI it was less. This technically did not make sense, but i decided to comment out sd_app_evt_wait function until i get more results. But I am not able to reproduce this anymore. So i think this comment is the problem on SDK 15.

Please change line 231 in port_cmsis_systick.c to below

#ifdef SOFTDEVICE_PRESENT
            if (nrf_sdh_is_enabled())
            {
                uint32_t err_code = sd_app_evt_wait();
                APP_ERROR_CHECK(err_code);
            }
            else
#endif

I will try to push these changes to official SDK for the next release.

[Elias Löwe]

I tried this actualy...

If I use  sd_app_evt_wait(), then average consumption is about 7mA (without DCDC) and 5mA (with DCDC enabled).

Something is definitely wrong there.

[Elias Löwe]

But on Sparkfun with demo app it dropped down to cca 200uA

[Susheel Nuguru]

the average power consumption with connected state? debugger on?