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ADS1217 DATA reading

masoud hosseini
Prodigy 60 points
Other Parts Discussed in Thread: ADS1217

Hi

I have using an ads1217 and i can read all registers and it seems the values are default even i can write in the registers but the problem is when i send read data "01" command i just read back 7f ff ff . i connected ain0 and ain1 as differential input to 1.7 volt. please help me.

thanks

  • 0
    TI__Guru** 113765 points

    Hi Masoud,

    Welcome to the forum! It would appear that you are getting a full-scale reading.  This may be due to using an improper or floating reference.  Make sure that a valid reference is connected.  When using the ADS1217 reference you must make an external connection from REFOUT to REFIN+, and REFIN- must be connected to AGND.  If you are still having issues, please send me your schematic, and all your register settings.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points
    Hi Mr benjamin,
    I appreciate your response I sent you schematic and pcb and the code that i interface with ads1217 and I have to say my Vref+ and Vrefout are connected to gether by soldering a wire. and that voltage is 2.5V.
    my all register values are defaults of datasheet.
    Best regards,

    Masoud H
  • 0 in reply to masoud hosseini
    TI__Guru** 113765 points

    Hi Masoud,

    Pin 48 must go to AGND.  Your schematic and layout show that it is going to a capacitor. Try replacing C18 with a short to AGND.  Also make sure that all pins connecting to AGND or DGND are truly connected at the device as shown in the pin configuration on page 6 of the ADS1217 datasheet.  AGND and DGND must also connect together.  I believe your header allows for this provision, but make sure that the connection is made.  It is very easily to damage the device if the grounds are not connected.  The maximum rating is +/-300mV maximum difference between grounds.  I think your biggest problem is REF- is floating and needs to be connected to AGND.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points
    Hi Mr Benjamin
    I have to say your advice was very helpful and solved my problem.I totally forgot connecting Vref- to AGND(to be honest ,the connected capacitor to Vref- deflected my mind from connecting that pin directly to AGND). now i can read voltages completely true.
    Best regards,

    Masoud H