This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS1294R: About ADS1294R applications

Part Number: ADS1294R

Dear Ti experts,

Below is my customer's question about ADS1294R, could you give some advice about it? Thanks!

    I have a project that is using the ADS1294R as ECG signal acquisition chip. The ADS1294R runs in LP MODE and the sampling rate is set at 250 SPS. We use the standard ECG signal generator to send ECG signals. After analyzing the sampling data, we found that the sampling rate was only about 236 SPS, which leads to the deviation of heart rate calculated from the data collected by the chip. The waveform of one section of the data analysis is as follows:

The heart rate generated by the signal generator was 60 bpm, but the heart rate measured by the ADS1294R was 63 bpm. After analysis, if the difference between the two R waves is 250 points, the heart rate is 60 bpm, but the difference between the two R waves measured is 718-482=236 points. So the heart rate measured is 63 bpm. I wonder why there was a deviation in the sampling rate of ADS1294R. Are there any registers' setting I have misconfigured, or are the timing of reading the data incorrect?

On the other hand, the respiration data collected by ADS1294R is very accurate, which is basically consistent with the respiration signal from the signal generator.

 Another anomaly is that the ID read out from the register 0X00 of the ADS1294R is 0xC0, not 0xD0 described in the data sheet. If the ID of the chip that I read was not incorrectly, shouldn't the chip not work at all? Why can this ADS1294R run and collect data, although there are deviations in the data, or is it possible that the ADS1294R in my hand that is a pirated chip?

 Thanks!

  • Hi John,

    Thank you for your post!

    To check the data rate period, use an oscilloscope to probe the /DRDY output. The time between the falling edges is the data rate period for all 4 channels in the ADS1294R. It should be 4 ms for 250-SPS data rate. The only way the data rate could be slightly different is if the master clock frequency was scaled a littel slower than the default 2.048 MHz.

    The data looks correct in your plot, so you do not appear to be missing samples. Are you using RDATAC mode and reading every sample? Or are you using RDATA mode and reading by SPI command? Please share your CONFIG1 register setting.

    Often times, when the ID register value reads an incorrect value, the POR sequence is not correct. This can cause some internal programmed bits to be misread during power-up. A simple fix is to introduce an extra /RESET pulse after power-up. Check to make sure that you are following the power-up guidelines in section 11.1 of the datasheet.

    Best Regards,