This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1115: ADS1115: Config and result registers always read 0

Part Number: ADS1115

Tool/software:

Good morning.
I'm new to the forum.
unfortunately I have the same communication problem mentioned above with the ADS1115 chip. I cannot read the registers of the ADS1115 chip, 
both in the config register and in the conversion register. or rather the bytes read are always null.
I attach below the timings of the SCL and SDA signals that seem correct to me. If any of you have any suggestions you can make, they are welcomed.





I have already replaced 3 different chips but all three have the same problem, so I don't think it's a malfunction of the chip itself.
If you need other information, just ask. Thank you very much.


  • Hi Mateo,

    Is the Address pin tied to VDD?

    I agree that your I2C transactions look correct for writing to the configuration register (capture 1) and reading the configuration register (capture 2).

    What is your I2C SCL frequency?

    Is there a schematic available you can share?

    Have you tried using an oscilloscope to probe the I2C lines to verify what the digital communication looks like?

    Best Regards,

    Angel

  • Hi Angel and thanks for the reply.
    
    the address pin is set to Vcc. SCL's clock is 44.10 KHz.
    the ADS1115 module was purchased on Amazon. I have 5 pieces of which I have tested 3 and all 3 with the same null output response.
    On the board I use to drive the ADS1115, two 1kOhm pull-up resistors are mounted on the SCL and SDA pins,
    which in parallel with the 10KOhm resistors present on the ADS1115 module purchased give a total parallel value of approximately: 909.0909 Ohms, which I think would be fine. Below I send you the images of the data collected through the oscilloscope,
    and a connection diagram of my electronics with the ADL1115 module:









    If you need further information, just ask. Thanks again for the support Angel.

    Matteo.
  • Hi Mateo,

    Why are there 2 different pull-up resistors rather than just one?

    Are your microcontroller and ADS1115 operating at the same VDD voltage?

    Do the ADC and microcontroller share a GND connection?

    From your digital communication capture it appears as if SDA is being pulled up to 3.3V, but SCL is only being pulled up to 3V. Is this the case? This could be the reason you are not getting a response from the ADC.

    Best Regards,

    Angel

  • Hi Angel.
    very fair observation. I proceeded to equalize the two pull-up resistances. 
    I confirm that the microcontroller and ADL1115 are powered by the same power supply (gnd - 3V3).
    I'll share with you the new timings obtained following the change,
    but unfortunately, as you can see, the problem remains unchanged. I really don't know what I can do anymore.
    I don't know if you have any other possible ideas for solving this.
    thanks again.


  • Hi Matteo,

    What was changed that makes SCL 3.3V now rather than 3V as previously seen?

    I notice that the digital communication does not go all the way down to 0v (GND) when the logic is low. There are also some disturbances when SDA is low (circled in red).

    You might have some connection/grounding issues with your setup.

    It is also always possible that these are counterfeit parts, since they were acquired as a non-TI module through a third party (amazon) and not through ti.com.

    Have you considered using the official TI ADS1115EVM for evaluation purposes? ADS1115EVM-PDK Evaluation board | TI.com

    Best Regards,

    Angel