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ADS8167: ADS8167 could not communicate with SPI

Emrullah Dere
Prodigy 35 points
Part Number: ADS8167

Tool/software:

Hi,

We have encountered an issue with our integrated circuit during data transmission. Every time we send data, the integrated circuit echoes back the data we sent instead of providing the ADC data. This issue occurs in both on-the-fly mode and auto-sequence mode. Our conversion time is set to 5 microseconds. For auto sequence mode, we divided the 24-bit clock data to be sent into 8-bit pieces.24 bits were created with 8-bit pieces.

I have attached sample data for your reference. In the attached images, you can see that the SDI data is echoed back on the SDO line. Specifically, the SDO line is mirroring the SDI data rather than displaying the ADC conversion results.

Could you please provide insights into why this loopback is occurring and how we can resolve this issue to obtain the correct ADC data?

Best regards,

Emrullah

5707.şematik11.pdf

  • 0
    TI__Mastermind 39430 points

    Hello Emrullah,

    I do not see the SPI-Enable line changing to define each SPI frame beginning and ending.  Maybe you do not have it hooked up, but in order to debug, I also need to see the activity on this signal as well (ADS8167 /CS line).

    Also, which SPI mode are you using?  Default is SPI-00 if you do not change this after power-up.

    I also noticed you are using a Saleae logic analyzer.  If possible, please send the waveform capture file (*.sal) and I can open it using the logic analyzer software.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 35 points

    Hello Mr.Nicholas,

    Actually we are testing on our custom boards. For our custom board we could not reach to Chip select pin so easly thats why we did not show in this waveform. This CS pin works compliant to datasheet.

    We are using SPI-00 mode Phase disabled and polarity is low.

    Best Regards,

    Emrullah

    ads8167_logic.zip

  • 0 in reply to Emrullah Dere
    Prodigy 215 points

    Hello Mr.Nicholas,

    In our projects, we are planning to order 1000+  this IC and we got these errors during the development stage. We do not want to change this IC to another one so can we make a quick call to fix this issue? 

    Best Regards,
    Furkan

  • 0 in reply to Furkan Gungor
    TI__Mastermind 39430 points

    Hello All,

    I found part of the problem that can cause communication errors.  The SPI configuration for your processor is incorrect; it should be set to SPI mode 00 in which case data is launched (MOSI) on the falling edge of SCLK.  In your data, you are launching data on the rising edge of SCLK, which is the same edge the ADS8167 captures data on.

    It is possible for this to work, but the MSB on the MOSI signal would need to high at least 3ns before the first rising edge of SCLK.  You would need a high speed scope to verify if this timing requirement is met.  However, changing the SPI mode on your processor will ensure the timing requirements are being met.

    Also, please send me a list of all register writes you send to the ADS8167 after power-up reset so I can confirm nothing is missing for your intended mode of operation.  (You can also send another logic capture file as well and I can verify.)

    After proper SPI configuration, timing, and register values have been confirmed, if there are still issues, we can look at setting up a quick call.

    Regards,
    Keith Nicholas
    Precision ADC Applications

  • 0 in reply to Keith Nicholas
    Prodigy 215 points

    Hello Mr.Nicholas,

    We can communicate with ADS816 right now. We solved this bottleneck. This issue caused because schematic design. Right now only issue is we can not communicate with SPI Mode - 0. 


    Thanks for your interest.

    Best Regards,

    Furkan

  • 0 in reply to Furkan Gungor
    TI__Mastermind 39430 points

    Hello Furkan,

    O.K.  Please feel free to post any additional questions you may have. 

    Regards,
    Keith

  • 0 in reply to Keith Nicholas
    Prodigy 215 points

    Okey Nicholas,

    Thanks a lot.

    Best Regards,

    Furkan