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ADS8166: Auto Sequence Mode - SEQSTS Not toggling

Jason Haedt
Expert 3230 points
Part Number: ADS8166

Hello ,

We are using the auto sequence feature of the ADS8166 following the steps on page 34 of the datasheet to mimic figure 48.  But after we issue the start command our SEQSTS pin never goes high.  I see a note in SDO_CNTL4 that if you set the bit to 1 then it indicates the active status.  I am not doing that in my code today and I am just relying on the auto sequence to automatically drive the SEQSTS pin.  Is that wrong? Do I need to also program SDO_CNTL4 to 1 show the active status so that SEQSTS pin toggles?  What does that statement mean in the SDO_CNTL4 register about active status?

Here is what I am writing to the registers:

Addr: 0x1C, value of 0x02 (dev_cfg)

Addr: 0x80, value of 0xFF (auto_seq_cfg1)

Addr: 0x82, value of 0x01 (auto_seq_cfg2)

Addr: 0x1E, value of 0x01 (start)

  • 0
    TI__Mastermind 36290 points

    Hi Jason,

    Yes, my understanding is the SDO_CNTL4 register must be set to 0x01 in order for the SDO-1 pin to reflect the status of the sequence (SDO_WIDTH=0b, default).  If not set, then this pin will always be a Hi-z level and could float from ground to DVDD depending on the leakage currents present.  If set to 1, then the pin is active and will reflect the status of the sequence.

    Also note that in order to write to the SDO_CNTL4 register, the REG_ACCESS register must first be written 0xAA.

    All other register settings look correct for Auto Sequence Mode with Auto_Repeat=1, scanning through all 8 channels.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • +1 in reply to Keith Nicholas
    TI__Expert 3230 points

    Thanks for the feedback.  We did try this but we are still not seeing SEQSTS toggle on one of our board sets.  We did validate the timings of the configuration so now we are going to order parts and do an A-B-A swap to see if the problem follows the part or the board.