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Evaluate modulation methods for ultrasonic array

Category: Hardware
Product Number: EVAL-ADAU1466Z

Hello Slight smile

I have an EVAL-ADAU1466Z board and I want to use it for a 40kHz parametric loudspeaker array project. My goal is to evaluate different modulation methods like PWM, SSB, AM, etc.

My question is, can I use the board to implement these methods?

Thanks!

  •      Hello,

         This is quite an interesting project.  It is certainly possible to do AM and SSB modulation in a SigmaDSP.  I'm not sure about PWM, it depends on the scheme you envision.  Often the needed carrier frequency is too high for a SigmaDSP to handle.

         As you know, a 40 KHz frequency range requires a 96K sample rate.  Modulation products extending beyond 40 KHz demand a 192K rate.  The EVAL-ADAU1466Z board has its AD1938 codec hardwired in standalone mode, where it's stuck at 48K -- see page 18 of the EVAL-ADAU1466Z manual.  Thus, even though the ADAU1466 can work at 192K, you can't run any projects up there with this board.  I have seen some posts which suggest it's possible to modify the board -- perhaps an ADI engineer has the details on this.  You might consider using the EVAL-ADAU1467Z board instead of the -1466 board.  This board features a switch which selects between standalone mode and setting up the codec via SigmaStudio.  I wish that all the eval boards using -1938 codecs had this switch.

         Best regards,

         Bob

  • Thank you very much for the information, it really helped clarify things! I would like to better understand how I would modify the board but I couldn't find any relevant posts here (maybe I'm not using the correct search terms). Would it require a physical alteration of the board's circuit?

    Thanks again!

  •      Hello,

         I was able to find a few posts which mention the mod, like this one.  Yet they don't describe the mod.  Since the board has its -1938 hardwired via its pin connection(s) for standalone mode, the mod will involve cutting and re-routing traces.  I don't have access to the modification instructions myself.

         Bob

  • Thanks for the quick reply! I'll have a look at the link you provided.

  • Hello Bob,

    Thanks for your inputs as always.

    gdim,

    Here I have explained how to modify the board and program the Codec in ADAU1466Z board.

    The EVAL-ADAU1466Z board has its AD1938 codec hardwired in standalone mode, which means the codec runs only at 48 kHz sample rate in slave mode.
    If you want to run the codec at 192 kHz sample rate, you need to program the AD1938 codec. Here are some steps to program the codec.

    Step 1

    In the eval board, standalone mode is configured by connecting CIN, CCLK and CLATCH to the ground.

    So, you need to remove those R6, R9, R10, and R11 resistors.


    Step 2

    1. Add a single square header pin into the AD1938_/CLATCH test point located near R11 like below image.

    2. Connect/solder a jumper wire from the AD1938_CCLK test point near R10 to the SCLK test point located near Pin 10 of J1.

    3. Connect/solder a jumper wire from the AD1938_COUT test point near R9 to the MISO test point near U5.

    4. Connect/solder a jumper wire from the AD1938_CDATA test point near R6 over to the MOSI test point near J1.

    5. Add a 10 kΩ pull-up resistor on the AD1938_/CLATCH signal line test point. The CLATCH signal must be pulled up to the D3V3 power supply.

    This power supply is located to the left of the C20 capacitor like below.

    Step 3

    MODIFYING THE EVAL-ADUSB2EBZ (USBi)

    The EVALADUSB2EBZ PCB is a footprint for a 14-pin ribbon cable but only a 10-way ribbon is used. The unused pins are the extra SPI latch's,

    Solder a jumper wire with a female connector, like in the below image.

    Here you have 4 extra latches so you can use any one of them. You can see the respective settings in the USBi block in sigma studio.

    Step 4

    Connect USBi like below.

    Step 5

    The below image shows the required setup to control the DSP and codec using SigmaStudio. Drag the AD193x block to the Hardware Configuration tab from the Tree Toolbox.
    The SPI latch setting on the USBi Interface block must be changed from the default SPI 0x1 ADR0 to SPI 0x2 ADR0.
    So that the AD1938 codec uses the second SPI latch output of the USBi ,if you are using SPI 0X3 latch then use SPI 0x3 ADR0 in USBi interface.

    Choose the latch in the Sigma studio USBi interface based on which latch you took out from the USBi hardware.

    Step 6

    Here you have the IC 2-AD193X control register window. By using this window, you can change the AD1938 codec’s sample rate, clock mode etc...

    Regards,

    Harish

  • That's awesome! Thank you very much for the detailed instructions!

  • Thanks Harish for writing up the great response.

    I just want to chime in and say that this is from the EVAL-ADAU1452RevB user guide. This eval board is exactly the same as the EVAL-ADAU1466Z eval board so the modification instructions apply to both boards. 

    When we designed the 1466 board I used that design to update the 1452 eval board. It is so similar that if you check carefully on the board you can see one text label I forgot to update. If I remember right it says 1466_CLK_OUT instead of 1452. Slight smile

    Here is the link to the user guide.

    EVAL-ADAU1452REVBZ User Guide (Rev. 0) (analog.com)

    Dave T