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ADS1119: ADS1119 ADC Address Mixed Up

Charles Lin1
Intellectual 525 points
Part Number: ADS1119
Other Parts Discussed in Thread: ADS1118

I had ADS1119 in one of my project. I noticed that I can read the AIN0 data when I used AIN3 address, and AIN0 address gives AIN3's data. I have tried to troubleshoot by myself, I couldn't find any issues. Any advise will be helpful.

Here is my schematic, only AIN0 and AIN3 are being used currently. AIN0 is supposed to give back the reading from J10.

Here is the address for each channel in the datasheet

Here is the address definition, and the function in my code

However, I found that if I put the get_AIN0, I will get AIN3 channel's ADC data. Any ideas what is wrong here?

Thanks,

Charles

  • 0
    TI__Expert 4670 points

    Hello Charles,

    When the ADS1119 mux switches it does not begin a new conversion immediately but finishes the current conversion before switching the mux. So there might be in the worst-case scenario 23ms before the new data is ready. If you are reading the data too quickly after writing to the configuration register you will get old data from the device. When switching between different channels using the mux, we recommend using single-shot conversion mode so you can start the new conversion immediately. It looks like you are reading the data immediately after writing, so you are probably reading in the old data.

    If adding a delay doesn't fix the issue, you should monitor the I2C connection to ensure proper communication is taking place. If you can post a screenshot of an oscilloscope or logic analyzer monitoring the connection I could also take a look at it.

    Let me know if you have any more questions,

    Levi DeVries

  • 0 in reply to Levi Devries
    Intellectual 525 points

    Thanks for your answer, Levi. May I know where the 23ms comes from? I read the datasheet a couple more times, but I didn't see this number. I am using 90SPS here, therefore, I think the actual conversion time is 11.26 or 11.29, is it right?
     

  • 0 in reply to Charles Lin1
    TI__Expert 4670 points

    Hello Charles,

    Sorry, I just realized I was incorrect about the two conversions, that is true about our ADS1118 and ADS1X15 but not this device. You are correct that the time delay should be 11.26 for this device in continuous mode, or 11.29 for single-shot mode.

    Let me know if you have any more questions,

    Levi DeVries