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DAC161S997: COMMUNICATION ERRORS USING DAC161S997

Kobena Wiredu
Prodigy 30 points
Part Number: DAC161S997

I am using the DAC161s997 interfaced with a cortex M4 microcontroller for the SPI communication. The output is stuck at 3.37mA and as expected, changes to 21mA when i set the ERRLVL pin high. However, it is stuck in this error state. I get an errValue of 0x2300 (where errValue = DAC161_CONVERT_ERR_VALUE(errHigh_uA) & 0xff00;) as per your c code that i adopted. Could you explain to me what this could mean? Is there a guide for one to know the issue based on this errValue?

  • 0
    TI__Expert 5820 points
    Hi Kobena,

    Which C code are you referring to and what MCU are you using? Both 3.37mA and 21mA are default alarm current values. I would assume the errHigh_uA refers to programming the ERR-HIGH register (0x07) to set the upper alarm current value.

    If the device is at the device is at either of the error currents (set by ERRLVL pin) it means that one of the alarm conditions is met. By default the device has a SPI timeout of 100ms set. If a SPI write is not performed every <100ms the device will produce the error current. This can be disabled in the ERR-CONFIG register. To determine which error is occurring you can read the STATUS register (0x09).

    Are you using the EVM or your own hardware? If you are not using the EVM, can you provide your schematic for review?

    Thanks,
    Garrett
  • 0 in reply to Garrett Satterfield
    Prodigy 30 points

    Thanks for your response. I wanted to attach the schematic but struggling to do so. Same as the c code but is a zip file from under software.

    The mcu i am using is ATSAM4CMS from atmel/microchip ().

    I am using my own hardware but picked a lot from the EVM schematics.

    Regards,

    Kobena

    4to20mA.sch

  • 0 in reply to Kobena Wiredu
    TI__Expert 5820 points
    Hi Kobena,

    I am not sure about the details of this firmware or how easily it will port to MCU you are using. The most straightforward way to debug this is to monitor the SPI bus and see what is being written to the DAC161S997. Can you provide these waveforms? Also, it looks like your schematic file is blank.

    Thanks,
    Garrett
  • 0 in reply to Garrett Satterfield
    Prodigy 30 points

    4to20mA-4to20mA.pdfThanks Garrett....it's written in C and so was so easy to adopt....I will look into providing you with the waveforms.

  • 0 in reply to Kobena Wiredu
    TI__Expert 5820 points
    Hi Kobena,

    I don't see any issue with your schematic that would cause this issue. One thing to note if you are using HART the 1uF capacitor across Loop+ and Loop- is too large and will attenuate the signal.

    If the DAC161S997 output is at one of the error current values, it means one of the error conditions is being met as described in section 8.4 of the datasheet. I would suspect it may be the watchdog timer as it is enabled by default.

    Can you provide captures of the SPI transmissions between your MCU and the DAC?

    Thanks,
    Garrett
  • 0 in reply to Garrett Satterfield
    TI__Expert 5820 points
    Hi Kobena,

    Any update on this thread?

    Thanks,
    Garrett