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Waveform distortion in higher ODR

RU HUA
Prodigy 80 points
Other Parts Discussed in Thread: CC2541, ADS1293

Hi ,

I am working on wireless heart monitor using ADS1293 with CC2541.Everything went well until I adjusted ODR. When increase the ODR I got  waveform distortion.

Here is my test data:

It's OK when ODR=160Hz

 

Waveform distortion when ODR=320

Can anyone kindly help me to find out the reason for waveform distortion in higher ODR.

Many Thanks,

Ru Hua

  • 0
    TI__Expert 3350 points

    From the posted data, apparently  CC2541  is not catching up with the selected higher data rate programmed in the ADS1293.  You may have to run your system at a lower rate to avoid the distortion in the signal.

  • 0 in reply to Bahram Mirshab
    Prodigy 80 points
    This is precisely the answer, Thanks !
  • 0 in reply to RU HUA
    Expert 1245 points
    Hi,
    I am also working on the ads1293 ,but we have designed our custom board.Actually i do not have ecg simulator. So can i check my circuit using function generator?if yes then how to connect it to the ads1293 input channels?
    please help!
    thanks !
  • 0 in reply to Parth Dholakiya
    TI__Genius 16890 points

    Hello,

    You should be able to connect a function generator directly to the inputs.  You need to make sure that your signal at the pins of the ADS1293 are less than the maximum allowed signal and with the CMVR.  This is explained in section 8.3.5 of the datasheet.

    Mike

  • 0
    Prodigy 100 points
    Hi hua ru,

    Could you please let me know if you tried to send signals wirelessly with an ODR of 200 or 267 Hz?

    If you tried these ODR values, were the acquired signals clearer?

    Moreover, if somebody wants to avoid the digital filtering of the ADS1293 chip (by disabling the ECG filter through the DIS_EFILTER register) in order to increase the available bandwidth for each ODR and set it closer to the Nyquist frequency (with the digital filtering the available bandwidth bacomes approximately 5 times less than the corresponding sampling frequency ODR), do you think that this would work?

    Thank you in advance.

    Kostis
  • 0 in reply to Konstantinos Petkos
    Prodigy 80 points
    Hi Kostis, My suggestion would be that ODR=320 will be a suitable number. And it will be clearer than 160. If the CC2541 cannot pick up so many data, a memory chip maybe needs to store the ECG data. Best Regards, Ru Hua