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Original question:

ADS1256 continuous mode results in strange interim conversion values

ADS1256: Continous mode output strange for 30Ksampling rate

Rashmi Mhapsekar
Prodigy 70 points
Part Number: ADS1256

Hi,

I am working in continuous mode for single channel measurement at higher rate 30KSPS.

I am giving sine wave as input to ADC AIN0 channel.

Raspberry Pi is communicating with High Precision AD/DA ADS1256 board over the SPI.

I am using C program got it from github.

SPI clock is 1.92MHz.

I received 30Ksamples at output.

The issue is ~ 10K output samples  are noisy.

The datasheet says If there is a step change on the input signal while continuously converting, performing a synchronization operation to start a new conversion is recommended. Otherwise, the next data will represent a combination of the previous and current input signal and should therefore be discarded.

Is this statement applicable to Sine wave.

I also tried for constant DC input. I got same behavior.

Thanks in advance.

Rashmi 

  • 0
    TI__Guru**** 180931 points

    Hi Rashmi,

    I believe the hardware and code example you are talking about is not from Texas Instruments, is that correct?  Have you gone through the vendors Wiki and the various RaspberryPi forums?  We won't be able to help you with any performance issues that hardware may have.

    To your question about the sine wave - no, there should not be any 'input step' issues when applying a sine wave to the inputs of the ADS1256.  A square wave input would be the better example of the datasheet comment regarding discarded samples.

  • 0 in reply to Tom Hendrick
    Prodigy 70 points

    Hi Tom,

    Thanks for your response.

    We are using RPi and High-Precision AD/DA ADS1256  board.

    The code is got from github.

    Which is the board/controller used to measure 30K sampling rate of AD1256. 

    And which coding language used. 

    Thanks,

    Rashmi

  • 0 in reply to Rashmi Mhapsekar
    TI__Guru**** 180931 points

    The controller with the ADS1256EVM-PDK (our hardware) is TMS320 5000 series DSP, the code is C based.