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WEBENCH® Tools/ADS1232: ads1232

Gobinath P
Intellectual 545 points
Part Number: ADS1232

Tool/software: WEBENCH® Design Tools

We are currently working with a dual channel adc ADS1232 in doing so we faced a problem. We connected three of these adcs (adc1, adc2, adc3) with the MCU in which each has it own dedicated DOUT, PWDN and Serial CLK pins connected to MCU. The SPEED, GAIN0, GAIN1, A0 are connected commonly with the MCU And XTAL 2 not connected to GND. When reading adc1 individually with a single load cell adc1 outputs proper voltage from the load cell but the other adcs outputs junk values. I have checked the adc1 data from both channels  they are reading fine but the other adc2 & adc 3 are reading junk values. Does this mean that the adc damaged or the has faulty input?

  • 0
    TI__Guru** 113765 points

    Hi Gobinath,

    Regarding adc2 and adc3, I would verify that all of the digital pins are connected properly and nothing is floating (such as the TEMP pin that you did not mentioned.)  Make sure the reference voltage is valid, and the sensor output is properly connected to the ADC inputs and are within the correct common-mode input range.

    The issue could also be a communication, firmware or timing issue as well.  With an oscilloscope or logic analyzer you can check and monitor DRDY/DOUT of both devices.  Without reading data you should see the output pulse at the selected output data rate.  One other consideration is you must read out the data after the DRDY/DOUT transitions from high to low which signals end of conversion.  The data must be read out completely before the next conversion finishes or the data might get corrupted.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Intellectual 545 points

    Hi Bob ,

            In this conversation I attached some scope shots of DOUT and ADC ch1 and ch2 . check this....this scope shots all are without connecting input to the ADC

  • 0 in reply to Gobinath P
    Intellectual 545 points

    Hi Bob ,

    do you have any scope shots of DOUT ,SCK And PDWN When Without reading data Because you say it pulsing selected data rate when without reading data . if you attach the file it is very helpful for us 

             thank you

  • 0 in reply to Gobinath P
    TI__Guru** 113765 points

    Hi Gobinath,

    The first scope plot is interesting.  Are you turning the power on and off a couple of times?  The yellow trace starts out looking like something is poorly connected, then the second half of the trace starts to kind of look normal then stops.  The blue trace looks as if PDWN is held low.  I'm not sure what the second scope shot is showing.

    When you power up the ADCs, you should pulse the PDWN pin to make sure it starts properly.  Second thing is you need to make sure that the DRDY/DOUT is going to an input pin on the micro and not a pin that is driven.  Third thing is you need to make sure that there are the proper voltages at all of the digital input pins of the ADS1232.  There should be no floating digital input pins or you will see erratic behavior.

    I've attached below a scope shot of DRDY/DOUT on startup.  Here PDWN is pulsed after power-up forcing DRDY/DOUT high.  This will stay high through 4 complete conversions and then go low, and will pulse thereafter at the data output rate when no data is read from the device (no SCLKs sent).  The shot also shows the recommended PDWN pulse and self-offset calibration.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Intellectual 545 points

    Hi bob,

          I have some problem on ADC  input channe Pin numbers (11,12,13,14) and I also attached scope shot of the pin behaviour. that pin give 5V out  I dont no what happen there .

    thank you

  • 0 in reply to Gobinath P
    TI__Guru** 113765 points

    Hi Gobinath,

    If this scope shot is showing what you are seeing on the analog inputs, this appears to be a specific pattern and not a floating input.  So there could be digital signals shorted to the inputs in some way.  If you click on my name at the top of the post you can open a private conversation with me and send me your schematic and PCB layout.

    Were you able to see the DRDY/DOUT and compare to the shot I provided earlier?

    Best regards,

    Bob B