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]

Ok, so you are using the UART to print log statements? By EVENTS_xxxx I mean the EVENTS registers for each of the peripherals, e.g. the UART event registers listed here: UART Registers

EVENTS_CTS	0x100	CTS is activated (set low). Clear To Send.
EVENTS_NCTS	0x104	CTS is deactivated (set high). Not Clear To Send.
EVENTS_RXDRDY	0x108	Data received in RXD
EVENTS_TXDRDY	0x11C	Data sent from TXD
EVENTS_ERROR	0x124	Error detected
EVENTS_RXTO	0x144	Receiver timeout

If any of these registers are set to 1, i.e. there is a pending event, then sd_app_evt_wait will return immediatly.

Best regards

Bjørn

[lydie]

Yes! Ok, and how can I know if any of EVENTS_xxxx are set to 1?

[bjorn-spockeli]

Well, you could print the values with the UART interface or monitor the registers of the peripherals in debug session.

[lydie]

Yes, but where? I printed in all handler function of each service, but no events are called. 

[bjorn-spockeli]

Hi lydie, 

Sorry for not explaining this better. I would check the EVENTS_ registers just before  sd_app_evt_wait() is called in nrf_pwr_mgmt_run(). As I tried to explain in my previous comments, any pending events, i.e. if any EVENTS_ register for any peripheral isnt cleared prior to calling sd_app_evt_wait(), then sd_app_evt_wait() will return immediatly. 

Hence I would start looking at the EVENTS regisiters of the peripherals that you are using your application, e.g. UART and SPI . 

Best regards

Bjørn

[lydie]

Hi,

Ok, I will do that.

Thanks for your help!

[bjorn-spockeli]

Happy to help.