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ADS1115: Conversion Register reading issue in ADS1115.

Snehal Nigudkar
Prodigy 10 points
Part Number: ADS1115

Hello,

Currently we are interfacing ADS1115 with ST32F446ZE micro-controller.

ADC Mode : Continuous conversion mode/Single ended input

configured alert pin as conversion ready signal. Controller will get external interrupt when conversion ready pulse occur.

Currently using channel A2 .

FSR bits : 4.096

VDD : 3.3V

Samples : 8 SPS

Config register setting : 0xE208

Hi threshold register : 0x80000

Lo threshold register : 0x0000

Result :

For 3.3 V analog input : Conversion register reading : 0xFFFF

For 2.0 V analog input : Conversion register reading : 0xFFE5

For 1.5 V analog input : Conversion register reading : 0xFF80

For 0 V analog input :  Conversion register reading : 0x0000

Query: I am configuring the ADS1115 in single ended mode so the output should be in the range of 0x7FFF according to datasheet .(Here the output looks like as if ADC is in differential mode)

Please help me. This is urgent....

Thanks,

Snehal Nigudkar.

  • 0
    TI__Mastermind 22950 points

    Hi Snehal,

    From what you sent, the configuration looks okay to me. Can you please provide a schematic so that I may take a look? If you do not wish to share it publicly, you can send me a friend request and share it privately. Additionally, some scope/logic analyzer shots of the I2C transactions would also be helpful. 

    Regards,

    Aaron Estrada

  • 0 in reply to Aaron Estrada
    Prodigy 10 points

    Sorry for late reply....

    Currently I have used STMF446 Evaluation kit and ADS1115 readymade board. I have checked the I2C communication part.I2C communication is ok as I have read the default values of config and threshold registers. I have also updated config register and read back. It is reading as expected.

  • 0 in reply to Snehal Nigudkar
    TI__Mastermind 22950 points

    Hi Snehal,

    So just to confirm, you are able to read the configuration register and it is showing expected results but the conversion results are still not as expected?

    You say that you are using an ADS1115 readymade board but did you purchase this from TI? If so, are you using the GUI to read back the results?

    Regards,
    Aaron