Basic mechanism of running examples for power efficiency

[Senchoi]

I'm quite new to nrf.

These days I'm trying to program power efficient uart data sender over ble.

It receives uart and sends data fine.

The problem is it's not going into sleep mode properly and consumes about 883uA or 544uA(DCDC mode) on idle.

But what I'm trying to understand is not just making this project into ultra low power uart data sender perfectly.

I'm trying to understand basic structure.

Even if I run ble_app_beacon example, I wonder why advertising signal repeats when the code is not in a for loop or while loop or a thread starter.

The beacon code looks like this

int main(void)
{
    // Initialize.
    log_init();
    timers_init();
    leds_init();
    power_management_init();
    ble_stack_init();
    advertising_init();

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

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

as you can see, only the idle_state_handle is in the loop.

So when beacon app is not going into sleep mode between advertising signals,

I would imagine I'd have to look into other repeating commands like for loop or while loop but there's no such thing other than idle_state_handle which merely calls sd_app_evt_wait() so it can go to sleep mode.

in the uart project I'm working on, when the programmed nrf52840 dongle connects to the other device over ble,

It is also programmed to send received data from arduino(UART data) to the other dongle which sends received data to usb so I can check the data in the PC

This also doesn't go to sleep in between sending uart signals.

So I would also imagine I'd have to go into uart data sending function like uart_event_handle() but there is no for,while loop in this or thread starter for that matter.

So how should I debug similar projects?

I'm guessing there must be some order that I can understand so I could pin-point which spot(code) is causing excessive power consumption

or what I have to do before putting it into sleep mode.

[Hung Bui]

Hi Senchoi, 

For measuring current consumption , I would suggest to test with the ble_app_pwr_profiling example. The example is optimized for low power consumption. 

Regarding the current you are seeing, it could be related to logging module, you may want to turn off any RTT or UART logging. 

[Senchoi]

it seems logging is already disabled by NRF_LOG_ENABLED 0 in sdk_config.h

Although I'm going to have to test ble_app_pwr_profiling. If it works I would have to migrate functions to this example.

[Hung Bui]

I would suggest to also test with the peripheral\rtc example, just to see if you can get to the base sleep current. 
Please note that if you just measure the average current consumption you need to take into account the BLE activity (advertising, connection) if you have any. 

[Senchoi]

When I run ble_app_pwr_profiling, the current reaches bottom fine.

also i was able to get beacon program to sleep in between after I put zero on NRF_LOG_ENABLED and make it dcdc mode.

it seems uart peripheral dongle does something related to uart connection when there’s no data to send over ble.

It consumes minimum of 9mA when it’s not connected to uart cables, 544uA when it’s connected to uart cables.

could it be because it consumes something to constantly listen to uart signals or to maintain ble connection?

[Hung Bui]

Hi Senchoi, 
Most likely when not connected to UART Cable the CPU is held waiting in a loop. But 9mA is quite high, it's higher than CPU active mode. You may want to use a power profiler to check what exact the current draw looks like. 

When connected to UART, and if the device staying in UART RX to wait for data, then 544uA is explainable, it's the UART peripheral and the HFCLK used. 

Which hardware are you using ? is it the nRF52840 dongle ? 

[Senchoi]

Yes it’s that dongle.