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ADS1256: Status register

Marvin Gasis Arcangel
Expert 8970 points
Part Number: ADS1256

Hi Team,

Can you help with the issue below?

I am attempting to read the status register, and online it seems to be that the four factory ID bits should be 0011 for 3. However, I consistently measure alternating 6s and 0s. Timing issues aside, is it possible to find out what the default status register for my chip should be?

That is to say, are all ADS1256 factory ID bits 0011?

Regards,

Marvin

  • 0
    TI__Guru** 112765 points

    Hi Marvin,

    Unfortunately I do not have a quick way of verifying the ID bits for the ADS1256.  To verify the communication I would suggest attempting to read a register with a known RESET value that is specified in the datasheet instead.  These would be any of the registers 1 through 4.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    TI__Expert 8970 points

    Hi Bob,

    I have a follow-up question.

    Hypothetically, a ADS1256 is running at 30 ksps (using the DRATE register), and using the ADS in a differential fashion for all 4 differential channels. How does this work exactly? Are each of the four channels being measured at 30 kHz, and then I get 120 kHz worth of data through SPI (30k for each channel)? Or is the 30k split up between the four channels so each channel is actually being measured at 7.5kHz. If this is the case, are each of the four channels being measured at a different time?

    Regards,

    Marvin 

  • 0 in reply to Marvin Gasis Arcangel
    TI__Guru** 112765 points

    Hi Marvin,

    This information is actually given and explained in the ADS1256 datasheet on page 21.  To measure four separate differential mux inputs, you have to cycle through the mux as there is only a single ADC.  The maximum data output rate is 30ksps, but for a single conversion continuously.  However it takes a number of conversion cycles for the digital filter to settle when cycling through the mux.  So to convert a single differential input it takes a period of 228.6us (1/4374Hz as shown in Table 14) for a single differential input channel.  To measure 4 separate channels it takes 4 * 228.6us = 914.5us to measure all four (or about 1.1kHz total throughput to capture all data continuously).

    Best regards,

    Bob B