On 1 April 2015 16:15:33 BST, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
>On 04/01/2015 05:02 PM, Daniel Baluta wrote:
>> On Wed, Apr 1, 2015 at 5:39 PM, Lars-Peter Clausen <lars@xxxxxxxxxx>
>wrote:
>>> On 04/01/2015 04:04 PM, Daniel Baluta wrote:
>>> [...]
>>>>
>>>>
>>>>> +static const struct iio_chan_spec_ext_info ltr501_ext_info[] = {
>>>>> + {
>>>>> + .name = "intr_persist",
>>>>> + .read = ltr501_read_intr_prst,
>>>>> + .write = ltr501_write_intr_prst,
>>>>> + .shared = IIO_SHARED_BY_TYPE,
>>>>> + },
>>>>> + {},
>>>>> +};
>>>>> +
>>>>
>>>> Would be nice to standardize persistence attribute
>>>> (IIO_CHAN_INFO_PERSISTENCE).
>>>
>>>
>>> If I understand the behavior correctly it causes that the event
>needs to be
>>> triggered at least n times before the event is reported by the chip.
>In my
>>> opinion 'persistence' is not a good term for that. I'm not sure what
>a
>>> better term is but I think it should go more in the direction of
>ratelimit
>>> or something.
>>
>> I've seen this term used for many devices:
>>
>> * TSL25911 ambient light sensor [1]
>>
>> [ One set of thresholds can be configured to trigger an interrupt
>only when
>> the ambient light exceeds them for a configurable amount of time
>(persistence)
>> ]
>>
>> * TAOS TCS34725 ambient light sensor [2]
>> [
>> The interrupt persistence filter allows the user to define the number
>> of consecutive
>> out-of-threshold events necessary before generating an interrupt.
>> ]
>>
>> * Avago SAPDS-9950, Sensortek STK3310
>>
>> I think the TSL25911 datasheet best describes this parameter, as the
>> amount of time
>> that ambient light should exceed a threshold until an interrupt is
>generated.
>
>Ok, that makes more sense. I misunderstood the initial description as
>that
>the signal would have to go first above the threshold then below the
>threshold, and this for a number of times. Whereas it needs to exceed
>the
>threshold for a certain amount of time before the event is triggered.
>If it
>goes below the threshold before the persistence interval no event is
>triggered and the counter is reset.
See ABI docs for _period.
This is indeed very common...
--
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