Current consumption NRF52

RE: Current consumption NRF52

Stian Røed Hafskjold — Fri, 03 Feb 2017 08:47:59 GMT

When LD5 is flashing fast, I think it means that the JLink has not initialized the driver yet. I've seen this problem in linux, where I sometimes have to reset the kit in order for it to reinitialize the driver, if not it will just continue flashing. Can't remember I've seen this on windows though, but you can try to install the latest driver from here: J-Link Software and Documentation Pack

RE: Current consumption NRF52

Felipe Ribas — Thu, 02 Feb 2017 17:15:54 GMT

Sorry about that, I do have the MainRTC definition outside the functions. And the buffer and other stuff I literally copied the code from inside APP_TIMER_INIT macro anyways. I found the problem... I have no clue why but after I program, I turn on the board without the USB cable to measure the current but the LED called LD5 keeps flashing nonstop. I'm using external power supply set to 3.3V and I opened the SB9 to measure the current. But after just powering off and on again the LD5 goes off then I can sense 2.0uA. Funny that happened sometimes only... it seems only in the first time I power on the board right after programming it happens. Then all the other times it powers on normally without LD5 flashing and already measuring 2uA. I don't know if I was clear enough, but any tips about that?

RE: Current consumption NRF52

Stian Røed Hafskjold — Thu, 02 Feb 2017 16:01:29 GMT

I tested your code and seems like you forgot the APP_TIMER_DEF macro to initialize the MainRTC variable. Also you should use the APP_TIMER_INIT macro so the buffer size is initialized correctly. something like this:

#define PRESCALER 4095
#define TIMER_DELAY 1000
void run_ClockMode()
{
    nrf_drv_clock_init();
    nrf_drv_clock_lfclk_request(NULL);
    while (!nrf_drv_clock_lfclk_is_running());
    APP_TIMER_INIT(PRESCALER, 1, NULL);
    APP_TIMER_DEF(MainRTC);
    app_timer_create(&MainRTC, APP_TIMER_MODE_REPEATED, MainRTC_handler);
    app_timer_start(MainRTC, APP_TIMER_TICKS(TIMER_DELAY, PRESCALER), NULL);
}

I measured on this code and it gave me about 2uA in average between the timer interrupts.

RE: Current consumption NRF52

Felipe Ribas — Thu, 02 Feb 2017 13:19:04 GMT

Ok, I tested with only the WFE inside the loop. Now it dropped the current consumption. However, I still get around 12 uA. The code is exaclty like the first code on my original post but with WFE inside an infinite loop. Am I still missing to achieve "System ON, no RAM retention + RTC + LFRC = 1.2uA + 0.1uA + 0.6uA = 1.9uA"?

RE: Current consumption NRF52

Stian Røed Hafskjold — Thu, 02 Feb 2017 12:39:32 GMT

The difference is discussed in this post: devzone.nordicsemi.com/.../

In general, it is best to only use one WFE in the loop to avoid race conditions.

RE: Current consumption NRF52

Felipe Ribas — Thu, 02 Feb 2017 11:47:43 GMT

Very nice. I will test it right now and come back with the answer. Meanwhile, is there any practical difference between using only WFE or WFE;SEV;WFE in the loop?

RE: Current consumption NRF52

Stian Røed Hafskjold — Thu, 02 Feb 2017 11:30:52 GMT

You need to put the __WFE() inside the loop. Then it will wait for an event and return to the __WFE() in the loop after the event. The for(;;){} will keep the CPU running and consume about 4-5mA after it returns from the event. So for(;;){__WFE;} is correct. Then it will return to the IDLE state every time it returns from an event.

You need to calibrate if you want to get a higher accuracy, but it's not mandatory.

RE: Current consumption NRF52

Felipe Ribas — Thu, 02 Feb 2017 11:10:35 GMT

I am using the DK at the moment but I would like to use the internal RC clock anyways. Should I calibrate or something like this? And yes, I simplified a little bit the main function but the only difference is the endless loop after. I will edit now so you can see. Do you reckon it is just wasting energy on this infinite loop? I thought the __WFE() function was gonna block (sleep) until receive an event.

RE: Current consumption NRF52

Stian Røed Hafskjold — Thu, 02 Feb 2017 09:55:37 GMT

Seems like you are missing the main loop in your code. You main function should look like this:

int main(void)
{
    run_ClockMode();
    while(true){
         __WFE();
    }
}

Without the main loop the CPU will continue into unknown territory.

If the above was just an error when posting the code here on the forum, one other thing I can think of is that the lfclk_request function requests the external LF clock and that you don't have an external clock (crystal) on your board. If you are using the DK this shouldn't be a problem though.