RTC1 counter return to 0

[annapalu]

Hi all,

i use softdevice and app timer. I know that the softdevice use a RTC0 and app timer RTC1.

I would use a rtc to have a timestamp. but i see that after 512 second the counter come back to 0. Someon can clarify why?

Thanks, Anna

[cirlam]

I implemented a workaround for this by using a Repeated App-Timer, with the timeout handler going off the moment before it overflows.

To create timer:

 err_code = app_timer_create(&m_millis_id,
  APP_TIMER_MODE_REPEATED,
  timer_a_handler);

To start timer:

err_code = app_timer_start(m_millis_id, APP_TIMER_TICKS(511999, APP_TIMER_PRESCALER), NULL);
    APP_ERROR_CHECK(err_code);

Timeout handler:

   static void timer_a_handler(void *p_context) {
  overflow++;
}

You can then retrieve the timestamp from the code below

 void timestampGet(timestamp_t *ts) {
  uint32_t ticks, s, t;

  ticks = app_timer_cnt_get();

  s = ticks / TIMER_TICKS_PER_SECOND; // becomes >>
  t = ticks % TIMER_TICKS_PER_SECOND; // becomes &

  ts->seconds = overflow * ((1 << RTC_TICKS_BITS) / TIMER_TICKS_PER_SECOND) + s;
  ts->milli_seconds = t * (APP_TIMER_PRESCALER + 1) * (1000.0 / APP_TIMER_CLOCK_FREQ);
}

The code above is adapted from Clem Taylor's answer here (devzone.nordicsemi.com/.../). I had implemented his approach, but found the PPI based counting mechanism increased the current draw from 50ua to 500ua.

My code above feels like a bit of a hack, so any criticism/suggestions are welcome.

[annapalu]

thank you cirlam!

It's very useful, but what's the value of RTC_TICKS_BITS? Thanks