Using Arduino to Send Data to AD5781 DAC Register

Hello,

 

I am using an Arduino to send data to the AD5781 DAC register (I have the AD5781 evaluation board) -- specifically, in the big picture, I want to send data continuously from the Arduino to the DAC so that I can get a desired smooth waveform output from the DAC. However, I cannot seem to get an output from the DAC, and so I assume that there must be something wrong with the way I am interfacing the Arduino and DAC.

 

In order to help pinpoint the problem, I have drawn a timing diagram (attached) based on what I am trying to do and what I understand should be the proper method to communicate with the DAC register in order to write data to it from the Arduino.

 

Please let me know if you see any flaws in my logic / timing diagram / implementation.

 

For reference, here is a link to the AD5781 datasheet: http://www.analog.com/media/en/techn...ets/AD5781.pdf

 

Thank you for the help!

 

Neal

DAC-ArduinoTimingDiagramSPOT.pdf
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  • Hello,

    The VREF and VCC are set at +5 V (as indicated on the user guide for AD5781 EVAL) and the VDD is +15 V and VSS is -15V (within the range of operation given). I do not have a drawn schematic on hand but you can see off my code how the pins are connected between the Arduino and AD5781 EVAL. Essentially, pin 7 on Arduino UNO is connected to LDAC pin on AD5781 EVAL, etc.

    As for the waveform diagrams, I am not getting any output from the DAC (VOUT pin) as I mentioned previously, so I'm not able to see the waveforms for writing to control register and DAC register. However, I do have a picture of the waveform for the data being written to the DAC register, solely as a probing of the MISO pin on the Arduino SPI. I have attached this below (blue is MISO and yellow is SYNC for first image, and blue is MISO and yellow is SCLK for second image).

    Please let me know if you can help me figure out how to get an output from the AD5781, given my code and these diagrams. Not sure where I am going wrong still, and would appreciate any guidance.

    Thanks

    First Image:

          blue is MISO and yellow is SYNC for first image

    Second Image:

        blue is MISO and yellow is SCLK for second image

Reply
  • Hello,

    The VREF and VCC are set at +5 V (as indicated on the user guide for AD5781 EVAL) and the VDD is +15 V and VSS is -15V (within the range of operation given). I do not have a drawn schematic on hand but you can see off my code how the pins are connected between the Arduino and AD5781 EVAL. Essentially, pin 7 on Arduino UNO is connected to LDAC pin on AD5781 EVAL, etc.

    As for the waveform diagrams, I am not getting any output from the DAC (VOUT pin) as I mentioned previously, so I'm not able to see the waveforms for writing to control register and DAC register. However, I do have a picture of the waveform for the data being written to the DAC register, solely as a probing of the MISO pin on the Arduino SPI. I have attached this below (blue is MISO and yellow is SYNC for first image, and blue is MISO and yellow is SCLK for second image).

    Please let me know if you can help me figure out how to get an output from the AD5781, given my code and these diagrams. Not sure where I am going wrong still, and would appreciate any guidance.

    Thanks

    First Image:

          blue is MISO and yellow is SYNC for first image

    Second Image:

        blue is MISO and yellow is SCLK for second image

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