ticks_diff_get () is not correctly working

Hi,

Please check below for the ticks_diff_get () function.

static __INLINE uint32_t ticks_diff_get(uint32_t ticks_now, uint32_t ticks_old)
{
return ((ticks_now - ticks_old) & MAX_RTC_COUNTER_VAL);
}

I think this is wrong because it will give a wrong value when ticks_now is smaller than ticks_old.

Therefore, does it need to cast to a signed value like below?

static __INLINE uint32_t ticks_diff_get(uint32_t ticks_now, uint32_t ticks_old)
{
return ( (int32_t) (ticks_now - ticks_old) & MAX_RTC_COUNTER_VAL);
}

If you don't agree, can you explain why?

Appreciate your help.

Thanks.

0 user110902 over 4 years ago

Currently, the RTC tick counter is 24 bit number. ticks_now is going to be smaller than ticks_old when the RTC counter went over the max count.

Then, (ticks_now - ticks_old) is actually negative but the types are uint32_t so that the value will be wrong.

That's why I think (int32_t) casting should be needed.

Am I right?
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0 user15146 over 4 years ago

Hi,

I think it's not a problem, it is masked there with 0x00ffffff so if ticks now is less than old there will be negative result masked.

But, unrelated to this, we have starting from nRF5-SDK v16.0.0 a new App Timer v2, that replaces the now legacy app_timer.
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