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ADS1115: ADS111 Faster reading or paraleling reading

Part Number: ADS1115
Other Parts Discussed in Thread: ADS1015

Hello, 

I'm working with the ADS111 and the duration between readings is about 10ms but i need to make it faster or if it is a way to read the four inputs at the same time? This is posible?

I hope you can help me with this, 

Thanks!

Ricardo. 

  • Ricardo,


    You cannot read all four inputs at the same time. The ADS1115 uses a multiplexer at the front of the ADC. This is basically a switch, so you can only switch in one switch at a time to make a measurement. The block diagram is shown below:

    However, you should be able to get data from the device much faster than every 10ms. The fastest data rate setting for the device is 860SPS (it's an even faster 3300SPS for the 12-bit ADS1015). If you are using multiple channels of the ADC, I would use single-shot conversion mode for the device. Here's the sequence:

    1. Program the configuration register to make a conversion with the proper configuration.
    2. Wait the data period + an extra 10% + 20us. This is the time it takes to make a conversion with 10% to account for variation in the internal clock and an extra 20us to wake up the device after the last conversion.
    3. Read the last data.
    4. Repeat from 1 to start the next channel.

    At a data rate of 860SPS, this time period should be about 1.3ms for each conversion.

    If you are using multiple channels, I would not use continuous conversion mode. When the configuration is programmed, the configuration is not set until the conversion in progress is completed. This can lead to confusion over when the device receives the configuration, and when to collect data. Even if you use the ALERT/RDY pin to indicate the conversion completion, continuous conversion mode is usually more confusing to implement.


    Joseph Wu