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ADS1115: How to enable "conversion ready" mode on ALERT/RDY pin ?

Part Number: ADS1115

Hello,

I can read voltage from the ADC in single-shot, single-ended mode. However, I can't get the ALERT/RDY pin signal the end of a conversion (conversion ready mode). The ALERT/RDY pin is always high.

I set the COMP_QUE bits to 00 (assert after 1 conversion). But I'm having trouble to figure out what to write to the low and high registers. For the low threshold, I tried 0x0000. For the high threshold, I tried 0x8000, 0xFFFF, 0x0100.

Do I have to write to the low/high threshold register before of after the configuration register ?

Other information :

  • the ALERT/RDY pin is connected to 3.3V through a 10K pull-up resistor. No other connection but a test point (this is a test board)
  • COMP_POL = 0 (active low), COMP_MODE = 0 (traditional, shouldn't matter), COMP_LAT = 0 (no latch, shouldn't matter)
  • I checked the voltage read with a voltmeter : very good agreement

Regards

  • Stupid me, I did things in the wrong order (C++/Linux stuff). So, it does works with low thres = 0x0000 and high thres = 0x8000.

    I think the datasheet uses the term MSB for both most significant byte and most significant bit.

  • David,

    I'm glad you were able to answer your own question. With the digital comparator, all you need is the high threshold to be lower than the low threshold, and the alert trips on each conversion.

    Thanks for posting back. If you have any other questions for this or any other TI device, you can just start another thread.

    Joseph Wu