what is the principle of converting Ticks in to seconds

[karan]

Hello

I am trying to change the ticks value of Battery measurement interval (ble_app-prox example) but i am not able to understand how the ticks period is measured based on what i understood from the example 1s is equal to 1000ms so totally we are setting it to120s then the ticks period is equal to 120000 if am wrong please correct me and explain me the correct method my aim to see the battery level changing based on the battery -measure_interval any help would be greatly appreciated

thankyou

[Susheel Nuguru]

Assuming you are using nRF51 and using APP_TIMER (RTC1).

You initialize the APP_TIMER using the prescaler. lets say that the prescaler is 0 then your timer generates 32768 ticks per second.

The macro given in app_timer.h converts the milliseconds to number of ticks.

#define APP_TIMER_TICKS(MS, PRESCALER)\
            ((uint32_t)ROUNDED_DIV((MS) * (uint64_t)APP_TIMER_CLOCK_FREQ, ((PRESCALER) + 1) * 1000))

Above you see that if MS = 120000 and prescaler 0, which is 120 seconds then you will get Ticks = ((120000*32768)/(0+1)*1000) rounded up to integer = 3932160 ticks. This is telling you that the timer will put 3932160 (0X3c0000) in RTC compare register and when RTC is started and is running for this many ticks, then it will be 120 seconds.

Does this answer your question?

[Susheel Nuguru]

depends on your chip. From the info center i can read that nrf51422 has suppy range of 1.8V-3-6V. This means that 2.1V must be 0% because this is low of CR2032 battery. and 3.3 must be 100% (because most coin cell comes with 3.0V output).

in app_util.h change the function battery_level_in_percent like below

static __INLINE uint8_t battery_level_in_percent(const uint16_t mvolts)
{
    // We assume 3000 mV is 100% and 2100 mv (dead CR2032) is 0%  = (((mvolts - 2100) * 100)/900);
    return ((mvolts - 2100) /9);
}

from the above you can tell that your suppy voltage is (percentage * 9) + 2100 Remember that CR2032 will never get to 1.8V i guess, but the above example

and change BATTERY_LEVEL_MEAS_INTERVAL to appropriate interval you need. Remember that first time the drop will be from 100% to down drastically because we start the program with assumption of 100%