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TMDSCNCD280039C: ADC Reading Problem

Bharat Chauhan
Prodigy 220 points

Part Number: TMDSCNCD280039C

Hello Sir,

I am using TMDSCNCD280039C for my development project in which i have used ADC from A0-A8 .

When I was connecting A0 to 3.3V then in debug window A0 count showing 4096 that is Okay but for A1 count showing 2000 and A2 count showing 1000.

A1 and A2 channels are opened not connected any where still it's showing random count.

Is it hardware problem or firmware side problem.

Kindly suggest reason for the same and how to resolve it.

Regards,

Bharat

  • 0
    TI__Mastermind 42330 points

    Hi Bharat,

    Can you check what ADC VREF is used (INTERNAL/EXTERNAL) from S3 switch position?  Also, what connections are present in channels A0-A8 in your setup?  I'm assuming you have connected the control card to the dock so you have access to A0-A8 channels.  If there are no connections made on A0-A8, meaning they are floating then that explains why you would be getting random readings on these channels.

    You should only expect deterministic values from ADC count if you have deterministic signal at ADC channels A0-A8 and VREF is properly selected.

    Regards,

    Joseph

  • 0
    Prodigy 220 points

    Hello,

    I am using Internal reference for ADC. I am not using any dock board . I am giving 3.3V to analog channel A0 from TP2 (3.3V) of control board through wire. At the same time all other analog channel are open still it is showing random count.

    Regards,

    Bharat 

  • 0 in reply to Bharat Chauhan
    TI__Mastermind 42330 points

    Hi Bharat,

    With the rest of the analog input floating, you will get random conversion counts.  That behavior is expected and it is not a hardware or firmware problem.  You have to either connect the rest of the channels to known signal sources or not convert/use them or connect them to VSSA if unused.

    Regards,

    Joseph