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Original question:

PGA970: PGA970EVM Wave No Longer being Generated

PGA970: PGA970 GUI is not generating waveform

ismail polat1
Intellectual 265 points
Part Number: PGA970

Hi,

I'm working to generate excitation waveform with PGA970's GUI with digital interface not MCU. However I cannot see any waveform from PI or P1-2 pins. AFAIK problem related with waveform ram.

GUI's generating LUT values properly and it writes that to waveform ram. I able to read this value from ram and they are correct.

However when I click the "generate" button, waveform ram changed to two meaningless value and there is no any signal output from PI pin.

I checked Vref voltage and all supply voltages including IC's internal regulators, there is no problem. Registers for waveform generation looks normal. I tried to write register values manually but when I set the waveform gen to enable, waveform ram values disappears.

Also I have read this related question: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1085986/pga970-pga970evm-wave-no-longer-being-generated?tisearch=e2e-sitesearch&keymatch=Pga970%20waveform%20generation#

Maybe I should load hex to fram but I cannot understand what is the role of fram in waveform generation and where are these hex files? Could you advice any solution?

Regards,

  • 0
    TI__Mastermind 31655 points

    Hi Ismail,

    The FRAM would be used if the PGA970 was running from the internal M0 MCU. In firmware, the output waveform would be stored in a lookup table that would then be copied to the waveform RAM to generate the primary side waveform. In digital interface mode with the M0 in reset, the waveform RAM should be all that is needed. 

    Can you confirm that the SPI communication is happening properly? You said that after loading the table you were able to read the waveform RAM and it matched? Can you try reading the full Low Level Configuration page? Does the output make sense? I would also put a scope or logic analyzer on the SPI pins to see how they are behaving during these transfers.


    Regards,

    Scott

  • 0 in reply to Scott Cummins
    Intellectual 265 points

    Yes, table values matched. SPI communication is working correctly bacause I can read and write waveform ram and registers properly. I checked device registers in low level configuration. For instance I can change common mode voltage of driver buffer with register settings. When I set the WAVE_EN bit, waveform ram values turns to two meaningless value.

  • 0 in reply to Scott Cummins
    Intellectual 265 points

    Hi Scott,

    When I load the generic firmware in to FRAM, device starts to working on microcontroller and digital interface both.

    I should ask again but is this hex code necessary for digital interface also?

  • 0 in reply to ismail polat1
    TI__Mastermind 31655 points

    Hi Ismail,

    If you do not plan to run the internal microcontroller, there is no need to program firmware into the FRAM.

    Regards,
    Scott