How can I get more time from the millis function?

RE: How can I get more time from the millis function?

Stefano1984 — Tue, 24 Jan 2023 09:47:28 GMT

Thank you

RE: How can I get more time from the millis function?

Einar Thorsrud — Mon, 23 Jan 2023 13:04:29 GMT

Hi,

Yes, if this never needs to run for as long as 49 days, then there is no problem to cast it to uint32_t.

RE: How can I get more time from the millis function?

Stefano1984 — Mon, 23 Jan 2023 10:55:10 GMT

Hi Einar Thorsrud,

thanks for the answer.

Currently I use the following code to make timings:

#define OVERFLOW			((uint32_t)(0xFFFFFF / APP_TIMER_TICKS(1)))

uint32_t millis(void)
{
    return (app_timer_cnt_get() / APP_TIMER_TICKS(1));
}

uint32_t ElapsedTime(uint32_t prevMillis)
{
    uint32_t currMillis = millis();

	// This statement is needed because millis() overflows approximately every 17 minutes.
    if (currMillis < prevMillis)
        return (currMillis + OVERFLOW + 1 - prevMillis);
    
    return (currMillis - prevMillis);
}

// Example:

uint32_t timer1 = millis();

while(1)
{
	if (ElapsedTime(timer1) >= 10000)
	{
		// Does something exactly after 10 seconds.
	}
}

Can I change my code and use the following?

uint32_t uptime_ms(void)
{
    return (get_now() / (uint32_t)APP_TIMER_TICKS(1));
}

uint32_t ElapsedTime(uint32_t prev_ms)
{
    uint32_t curr_ms = uptime_ms();
    
    return (curr_ms - prev_ms);
}

// Example:

uint32_t timer1 = uptime_ms();

while(1)
{
	if (ElapsedTime(timer1) >= 10000)
	{
		// Does something exactly after 10 seconds.
	}
}

Specifically can I cast it to uint32_t?
In this case there is no need to manage the overflow because the overflow time is very long (my device can stay on for max 2 days) right?

Thanks for your time

RE: How can I get more time from the millis function?

Einar Thorsrud — Mon, 23 Jan 2023 08:45:35 GMT

No, it returns the internal counter value. Essentially the same as app_timer_cnt_get(), but where that returns a uint32_t with the 24 bit counter directly from the COUNTER register of the RTC, get_now() returns a uint64_t that is always increasing. It comes from the COUNTER though and has the same frequency, so you can calculate the time in milliseconds just as you did with app_timer_cnt_get(). I suggest you try both, and you should see that before the 24 bit counter wraps around, you will get the same result with both.

So that would be something like this:

static uint64_t uptime_ms(void)
{
    return (get_now() / (uint64_t)APP_TIMER_TICKS(1));
}

Note that here I return an uint64_t. You can cast it to uint32_t and use that, but note that counting milliseconds in a uint32_t will mean that it will overflow after a bit more than 49 days.

RE: How can I get more time from the millis function?

Stefano1984 — Fri, 20 Jan 2023 15:01:02 GMT

I'm using a NINA-B3 module where the nRF52840 microcontroller is present.

RE: How can I get more time from the millis function?

Stefano1984 — Fri, 20 Jan 2023 14:46:08 GMT

Thanks for the answer but I don't understand what get_now returns. Milliseconds like millis?
How do I get milliseconds?

RE: How can I get more time from the millis function?

Einar Thorsrud — Fri, 20 Jan 2023 13:02:13 GMT

Hi,

If you are using a recent SDK and the app_timer implementation is app_timer2.c, then this is quite straight-forward, but you need to do a small change in the app_timer. The app_timer2 implementation use a 64 bit counter internally, so what you could do is to make get_now() non-static, and add that to app_timer.h as shown in this diff:

devzone.nordicsemi.com/.../app_5F00_timer_5F00_get_5F00_now.diff