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ADS1218: DYDY related issue.

Mohd Asim
Prodigy 10 points
Part Number: ADS1218

Hi All,

IN ADS1218, user is suppose to read the data when DRDY goes low. Is it mandatory to read this data in every DRDY low cycle? Let us say I read the data after few DRDY cycles, will I get the correct data i.e. the data of the current cycle or I get the corresponding to the older DRDY.

Regards,

Asim

  • 0
    TI__Guru** 113765 points
    Hi Asim,

    Welcome to the E2E forum! It is not required for you to read the data each time DRDY transitions from a high state to a low state. DRDY is used as a signal that new conversion results are available. The results are saved until the next DRDY transition when new results become available.

    All that said, the result is based on the digital filter settings used. See the Digital Filter section on page 18 of the ADS1218 datasheet. Depending on the filter order, a sinc filter will be settled based on the order of the filter which also relate to the number of conversions required. So if the sinc3 filter is used, then the previous 2 conversion results are also a part of the settled data result. If a large step change takes place on the analog inputs, this data will take a number of conversions to become fully settled.

    If the Auto filter setting is used, then the filter order changes with increasing conversions so that after the first conversion the following results will always be valid with increasing sinc order until sinc3 is reached.

    A little confusing I know, but the answer to your main question is you do not need to read each result. Let's say you read the 5th conversion result skipping the first 4. No matter what filter setting is used your data is valid. If you skip the next 10 conversion results, the next result you read is valid unless there was a large input voltage step just prior to reading the result which may take several conversion results to show the proper result.

    Best regards,
    Bob B