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ADS1192 always misses R wave in ECG acquisition

Xianwen Zhang
Prodigy 100 points
Other Parts Discussed in Thread: ADS1192

Hope someone can help me.

I used ads1192 to sample the ECG.  When I plotted the conversion data, I found R waves were often missed in conversion results. the figure below is the ECG sampled from a healthy subject and most of the R waves were missed. I do not know why.

    

The register configuration are as below:

writeRegister(0x41,0x02);/

writeRegister(0x42,0xb0);


writeRegister(0x43,0x11);


writeRegister(0x44,0x60);


writeRegister(0x45,0x60);
writeRegister(0x46,0x21);
//
writeRegister(0x47,0x00);
writeRegister(0x48,0x00);
writeRegister(0x49,0x02)


writeRegister(0x4A,0x82);
writeRegister(0x4B,0x00);

  • 0
    TI__Guru**** 175431 points
    Hi Xianwen,

    Welcome to the e2e forum! Have you connected your ADS1192 to a patient simulator? That would be the first place to start. The problem is most likely in your cabling or electrodes. I don't see anything in your register settings that would cause a problem.
  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    Hi Tom,

    I used the ECG simulator to generate ECG waves and connected it to channel 1.  the R waves were still missed and some of the R waves are small. see the plot of the conversion data.

    The picture below shows the setting of the ECG waves. the frequency is 1 Hz;  the amplitude is 200 mV; the offtset is 200 mV. and these parameters are accord with the conversion data. 

    The registers are not changed. could you explain why the R wave were missed or become smaller ? 

    I wonder if there is some problem in the shematic, and I post it below. Could you help me check it ? I wonder if the resistor and capitance in channel 1 are correct. 

    Thank you !

    Xianwen Zhang 

  • 0 in reply to Xianwen Zhang
    TI__Guru**** 175431 points
    Hi Xianwen,

    Can you try putting in a sine wave insted of the ECG wave form (keep the same amplitude and frequency)? The plot above looks like it's missing samples, can you verify that your SPI interface is reading all data out of the ADS1192 between the DRDY pulses?
  • 0 in reply to Tom Hendrick
    Prodigy 100 points

    Hi Tom,

    I put a sine wave and square wave into che channel 1 of ADS1192. The parameters of the wave were not change. The frequency was 1 Hz; The amplitued was 200 mV; The offset was 200mV; The  duty cycle of the square wave was 50%. The plots of the conversion data are showed below.

    1. Square wave. The duty cycle seems not accarate.

    2. Sine wave. 

    From the result of the sine waves, we can see the data were not continuous. I agree that the sample data were missing or not read correctly, but how to verify whether the conversion data was read correctly or not by SPI interface.  How to do this in my firmware ?  

    Thank you for your help.

  • 0 in reply to Tom Hendrick
    Prodigy 100 points
    Hi Tom,

    I figured out why the samples were missing. I should read the data in the DRDY interruption to make sure all the conversion data are read out, and the probblem is solved. It is a problem of my firmware.

    Thank you for your help.
  • 0 in reply to Xianwen Zhang
    TI__Guru**** 175431 points

    Great news!  Thanks for letting us know!