Current consumption ble

[lydie]

Hi,

I'm using nrf52832 with s132, so I don't find any information about the current consumed by the device when I'm connected by Bluetooth. I use the driver st7735 and an LCD screen. When my phone is not connected by Bluetooth and my device sleep, the current is 0.43mA. When my phone is not connected, and the LCD screen is ON, the current is around 3.4mA. Until then, everything is normal. But when I'm connected and my device is sleeping, the current is 1.5mA, and if the screen is ON the current is 0.7mA. So I don't understand why the current is increased when I'm connected and when my device is sleeping? And why the current decrease when the screen displays something. On online power profiler, the power consumes when there is a connection but the device is asleep is not indicated, so I don't know if it is normal or not. 

Thanks,

Lydie

[bjorn-spockeli]

Hi Lydie, 

which S132 version and SDK version are you using? 

All the BLE examples in our nRF5 SDK will go to sleep when the CPU is idling, i.e. in between connection events and advertisment events. Our SoftDevice is 100% event driven so, whenever the nRF is in the main for() loop it will call idle_state_handle(), which in turn calls nrf_pwr_mgmt_run(), which in turn calls sd_app_evt_wait() or __WFE(). These functions will make the CPU sleep until there is an interrupt or event that wakes up the chip, i.e. a timer expiring or a BLE event like advertisment or a connection event. So as long as you're calling idle_state_handle() in the main for loop, the nRF should go to sleep in between connection events. 

void nrf_pwr_mgmt_run(void)
{
    PWR_MGMT_FPU_SLEEP_PREPARE();
    PWR_MGMT_SLEEP_LOCK_ACQUIRE();
    PWR_MGMT_CPU_USAGE_MONITOR_SECTION_ENTER();
    PWR_MGMT_DEBUG_PIN_SET();

    // Wait for an event.
#ifdef SOFTDEVICE_PRESENT
    if (nrf_sdh_is_enabled())
    {
        ret_code_t ret_code = sd_app_evt_wait();
        ASSERT((ret_code == NRF_SUCCESS) || (ret_code == NRF_ERROR_SOFTDEVICE_NOT_ENABLED));
        UNUSED_VARIABLE(ret_code);
    }
    else
#endif // SOFTDEVICE_PRESENT
    {
        // Wait for an event.
        __WFE();
        // Clear the internal event register.
        __SEV();
        __WFE();
    }

    PWR_MGMT_DEBUG_PIN_CLEAR();
    PWR_MGMT_CPU_USAGE_MONITOR_SECTION_EXIT();
    PWR_MGMT_SLEEP_LOCK_RELEASE();
}

static void idle_state_handle(void)
{
    if (NRF_LOG_PROCESS() == false)
    {
        nrf_pwr_mgmt_run();
    }
}


/**@brief Function for application main entry.
 */
int main(void)
{
    // Initialize.
    log_init();
    leds_init();
    timers_init();
    buttons_init();
    power_management_init();
    ble_stack_init();
    gap_params_init();
    gatt_init();
    services_init();
    advertising_init();
    conn_params_init();

    // Start execution.
    NRF_LOG_INFO("Blinky example started.");
    advertising_start();

    // Enter main loop.
    for (;;)
    {
        idle_state_handle();
    }
}

If its not going to sleep, then there must be a pending event/interrupt that keeps the CPU from sleeping, i.e. causes sd_app_evt_wait() or __WFE() to return immediately. 

On online power profiler, the power consumes when there is a connection but the device is asleep is not indicated, so I don't know if it is normal or not. 

 The online power profiler will calculate the average current consumption with the assumption that the CPU goes to sleep inbetween connection and/or advertisment events. 

Best regards

Bjørn

[lydie]

Hi,

I'm using sdk15.3. Ok I understand, so to decrease the current, I have to find which event or advertisement prevent the CPU from sleeping. But I haven't found any events. I tried with cts example, but the current neved decreases when I'm connected.

Thanks for your reply.

Lydie

[bjorn-spockeli]

How are you measuring the current consumption, i.e. setup? What type of measurement hardware are you using?

 

lydie said:

I tried with cts example, but the current neved decreases when I'm connected.

 The default CTS example, i.e. nRF5_SDK_15.3.0_59ac345\examples\ble_peripheral\ble_app_cts_c ? No changes made?

[lydie]

I'm using a serial amperemeter. + is connected to my gbf, and the com VDD of my device. Yes CTS example and I haven't made any changes.

[bjorn-spockeli]

Which specific amperemeter? What is the resolution of the amperemter? It needs to have a dynamic range able to accurately measure currents from nA to mA. 

[lydie]

I don't know, it is a multimeter. But I can see the current which decreases when my phone is not connected by Bluetooth so the problem is not the amperemeter. I disabled all timers, so if they are no advertising (on_adv_evt not called), after 10 sec (APP_ADV_DURATION  1000), sleep_enter_mode must be called, but it's not the case. I don't see what type of event can prevent sleep mode from being activated.