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ADS1298R: ADS1298R

William Yangjaya
Prodigy 120 points
Part Number: ADS1298R
Other Parts Discussed in Thread: ADS1298

Hello,

I'm currently using ADS1298R and Raspberry Pi 4, and having a trouble in using it in 1K SPS.

I already used clock divider 128 and 256.

I am confused in determining the best clock divider.

Sometimes, I got satisfied result.
After the good result, I don't get the good result again.

Why the results like these are happening? Am I doing something wrong? Should I send my code here?

  • 0
    TI__Guru 55062 points

    Hi William,

    I cannot help you debug your Raspberry Pi since it is not a TI product. If you have a direct question for the ADS1298, I will do my best to help. 

  • 0 in reply to Alexander Smith
    Prodigy 120 points

    Hello,

    I have a direct question for ADS1298.
    I want to acquire ECG signal 12-lead from all channels using freq. samp 1K SPS in 20 seconds.
    How can I get exactly 20,000 data?

    Is there a clock divider effect of the excess or shortage of data obtained?

    Can you suggest what clock divider suits my needs?

    Thank you

  • 0 in reply to William Yangjaya
    TI__Guru 55062 points

    Hi William,

    Ah, I think I understand better now.

    The nominal frequency for an external clock is 2.048MHz.

    The modulator samples the input signal at the rate of fMOD = fCLK / 4 for high-resolution (HR) mode and fMOD = fCLK / 8 for low-power (LP) mode.

    Then the decimation ratio, DR[2:0] in the CONFIG1 register sets the sample rate. 

    000: fMOD / 16 (HR Mode: 32 kSPS, LP Mode: 16 kSPS)

    001: fMOD / 32 (HR Mode: 16 kSPS, LP Mode: 8 kSPS)

    010: fMOD / 64 (HR Mode: 8 kSPS, LP Mode: 4 kSPS)

    011: fMOD / 128 (HR Mode: 4 kSPS, LP Mode: 2 kSPS)

    100: fMOD / 256 (HR Mode: 2 kSPS, LP Mode: 1 kSPS)

    101: fMOD / 512 (HR Mode: 1 kSPS, LP Mode: 500 SPS)

    110: fMOD / 1024 (HR Mode: 500 SPS, LP Mode: 250 SPS)

    Knowing the relationship between the clock, modulator, and resulting sample frequency depending on your sample mode should help you calculate the clock frequency you need.