Can you help me to connect Arduino with AD7718?

Hi,

I'm trying to connect the Arduino 2 board with the AD7718 using SPI interface.

I have followed the configuration instructions of the AD7718 datasheet but the ADC does not response. The data in ADC input (DIN) is correct (I have checked with the oscilloscope), but the DRDY signal is ever high and so the DOUT signal.

Attach my arduino code, if you want to check it.

Ale

ad7718.txt.zip
  • 0
    •  Analog Employees 
    on Apr 16, 2017 7:20 PM

    Hi,

    Can I have a scope shot of your digital interface? May I also ask for your schematic diagram? After powering up, can you perform a reset by writing 32 consecutive 1s to the device? This ensures that all registers are at their default values. Then, just try to read one of the on-chip registers. This will check whether the read function is working. Reading the ID register is the recommended method for verifying correct communication with the device. Following this, you can now configure the device by writing to the registers contents based on the configuration flow suggested on the datasheet. 

    Thanks,

    Jellenie

  • The problem is the signal on the MISO bus (DOUT on the AD7718). It does not pulled to GND (yellow signal in the attached figure below - blue signal is CS).

    The signals rappresent the ID register request.

    The schematic is reported in the figure below.

    I have tried to reset the ADC by 32 consecutive 1s but the result is the same.

  • 0
    •  Analog Employees 
    on May 7, 2017 10:28 PM

    Hi,

    Looks like your not getting a clean scope shot signals. I was thinking what could be those uneven pulses on your DOUT line and also that extra pulse on CS. Can you also include the DIN and SCLK scope shots upon requesting to read the ID register? Another thing, can you try to disconnect the DOUT pin of the AD7718 to the arduino DIN pin, then just try to read the DOUT line in scope shot, are you using the same results? Is there any other signals connected to your digital lines or it just directly connected to microcontroller? Does the DGNDs of AD7718 and microcontroller connected to each other?

    Have you also tried to put the device in continuous conversion mode by writing to the mode register and then pull CS low to monitor the RDY pin? Is it pulsing at the default/selected output data rate?

    Thanks,

    Jellenie

  • Hi Jellenie,

    I attach the image of CS, DOUT, DIN and SCLK signals after a request to read the ID register.

    I have tried to disconnect the DOUT pin of the AD7718 and I shot a scope of the signal.

    There is not other signals connected to the SPI interface between  ADC and microcontroller, and the DGNDs are connected to each other.

    The SPI baud rate is setted to 115200.

    Thanks for your collaboration,

    Alessandro

  • 0
    •  Analog Employees 
    on May 18, 2017 11:33 PM

    Hi, Alessandro.

    Can you try to put the device in continuous conversion mode by writing to the mode register and then pull CS low to monitor the RDY pin? Is it pulsing at the default/selected output data rate? You are using a crystal, can you have a look at this to ensure that it’s working correctly and tseeing the right waveform on this. Also ensure that the caps on the crystal are within the crystal manufactures guidelines.

    Thanks,

    Jellenie