• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 31 subscribers
  • Views 1155 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

PGA970: Detailed description of registers to get the phase information

Takuto_Yoshioka
Intellectual 360 points
Part Number: PGA970

Hello,

I am thinking about how to determine whether LVDT core exists left or right.

Now LVDT is connected 4-wire method. 

I guess that I need to use the registers below.

  • DAC_SIN_NDS1
  • DAC_SIN_NDS2
  • DEMOD1_PH1DATA
  • DEMOD1_PH2DATA
  • DEMOD2_PH1DATA
  • DEMOD2_PH2DATA

Refer to PGA970 datasheet, the description about these registers is surprisingly simple. 

I could not figure out how to use them. 

Could you give me more descriptions and example of use about the registers?

Thank you and best regards,

Takuto Yoshioka

  • 0
    TI__Mastermind 31655 points
    Hi Yoshioka-san,

    The DAC_SIN_NDS1 and NDS2 are the registers you set to select where you will sample the DEMOD output. the PH1DATA is the demodulator output at the sample specified by DAC_SIN_NDS1, and the PH2DATA is the output at the sample specified by DAC_SIN_NDS2.

    The simplest way to use this is as follows:

    At DAC_SIN_NDS1 = 0, the DEMOD1_PH1DATA = A*sin(phase)

    At DAC_SIN_NDS2 = WAVEFORM_TABLE_LEN, the DEMOD1_PH1DATA = A*cos(phase)

    You can calculate the phase by taking the arctan of the two data points:

    phase = arctan(DEMOD1_PH1_DATA/DEMOD1_PH2_DATA)

    Regards,
  • 0 in reply to Scott Cummins
    Intellectual 360 points
    Hello Scott-san,

    Thank you for your explanation.
    I understood well.

    Thank you and best regards,
    Takuto Yoshioka