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ADS1115: ADS1115 Long Internal Averaging Time

David Roberts
Intellectual 350 points
Part Number: ADS1115

Instead of using a CPU to average ADS1115 samples, I want to use the internal feature.Suppose I only use 2 channels and want to average each for 1 second. Here is a description of my program:

1. load config register with gain, continuous mode, channel 0, 860 SPS

2. wait for 1 sec while about 860 samples are averaged

3. read data

4 - 6 do the same thing for channel 1 as described in steps 1-3.

Questions:

Is the above description OK?

Does the act of loading the Config register cause the sigma/delta circuitry to forget the conversion result for the previous channel? If not the first of 860 samples may be completely wrong.

Is there a way of reducing power, since the I2C circuitry is seldom activated?

Thanks

  • 0
    TI__Mastermind 22950 points

    Hi David, 

    This sounds OK to me. If the device configuration is changed in continuous conversion mode, the previous configuration settings will still be used with the ongoing conversion. When a new conversion starts, the new configuration settings will be used. 

    For reducing power, using single-shot mode will be your best bet. In this mode, the device is in a power-down state until a 1 is written in bit-15 of the configuration register. An Ivdd comparison of operating vs power-down can be seen in the Electrical characteristics table. 

    Regards,
    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Intellectual 350 points

    Thanks, Aaron. If I select channel 0, 860 SPS, one-shot mode, then wait for one second, will the value that I read read by the average value for channel 0 over the 1 second?

  • +1 in reply to David Roberts
    TI__Mastermind 22950 points

    Hi David,

    I think I see what you are asking now. You can't really sample over a specific period of time with this device. The input is sampled many times the data rate (Oversampling) and then converted and put into the conversion register at a slower rate.  I think in this case, what you will need to do is to sample and convert at several points within 1 second and then average those results. In this case, continuous conversion would be useful but you would need to keep track of the conversions. 

    Regards,
    Aaron