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ADS1115 conversion start timing

NAOKI AOYAMA
Guru 11215 points
Other Parts Discussed in Thread: ADS1115

Hello,

My customer uses the ADS1115, using configuration as follows.

 ADS1115: configure data rate 8sps (1st config.)

wait 1s.

ADS1115: read result

wait 1s.

ADS1115: configure data rate 128sps (2nd config.)

wait 15ms.

ADS1115: read result

My customer uses 'continuous conversion mode'.

He cannot get the 2nd conversion result. He has a question.

When does it start '2nd config conversion' ?

Which is the start timing as soon as after write  the 2nd configuration or after the end of conversion of  1st configuration?

Regards,

Naoki Aoyama

  • 0
    TI__Guru* 97585 points
    Naoki-san,


    When the configuration is changed, the ADS1115 will first complete the conversion in progress and make the configuration change after the conversion. In this case, the first read may be from the previous configuration. Your customer could throw away the first read and then take the second read, or they could enable the conversion ready pin (as described on page 15 of the datasheet) to determine the conversion completion.

    Another option would be to use the single-shot mode for conversion this way, they could guarantee the conversion mode and then start conversions.

    When you say your customer cannot get the second conversion result, what do you mean? Are they getting bad data? Does the part not respond with a conversion? Are they getting data from the previous configuration?

    If your customer is still having problems reading the second conversion result after a configuration change, I would have them post the digital transactions (each byte) that they are sending to the device.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Guru 11215 points
    Hi Joseph-san,

    Thank you for your reply.

    I'm sorry for my poor explanation.
    They are getting data from the previous configuration.
    They repeat 'wait 15ms and read result' three or four times, they are getting data from the second
    configuration at last.
    So I want to know the start timing of the second configuration conversion.

    Thanks,

    Naoki Aoyama
  • 0 in reply to NAOKI AOYAMA
    TI__Guru* 97585 points
    Naoki-san,


    If the starts in 8sps mode, and then the ADS1115 is put into the 128sps mode, the device continues in that mode until it completes the conversion in progress.

    This means that once this device is told to go to 128sps, it may still be in the 8sps mode for 125ms depending on when the 8sps conversion started and when it was told to be in 128sps conversion mode. For this reason, it's generally best to use the single-shot mode. This allows the user to initiate conversions and start conversions when ready.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Guru 11215 points
    Hi Joseph-san,

    Thank you for your fast reply.
    I understood the start timing.
    I will feedback to my customer this information.

    Thanks,

    Naoki Aoyama